Review of Lead Crystal Battery
Technology
Report For
Energy Innovation Centre & their Clients
Part 2 – Main Report
Confidential to Client
Contract Reference: DIA150330_Stage 1
Prepared by John Brailsford
Reviewed by Richard Parke
Partners in Power Engineering
Review of Lead Crystal Battery
Technology – Part 2
Contents
1.
Introduction ........................................................................................................................14
2.
Scope and Objectives ..........................................................................................................14
3.
Background .........................................................................................................................14
4.
Lead-acid battery technology ..............................................................................................15
5.
6.
7.
8.
9.
4.1
Electrochemical reaction ................................................................................................. 15
4.2
Cell design ........................................................................................................................ 15
4.3
Electrode design ............................................................................................................... 16
4.4
Failure modes ................................................................................................................... 17
Lead crystal battery .............................................................................................................18
5.1
Design and technology ..................................................................................................... 18
5.2
Performance specification ............................................................................................... 21
5.3
Conclusions ...................................................................................................................... 29
Comparison with NiCad batteries ........................................................................................30
6.1
NiCad technology ............................................................................................................. 30
6.2
NiCad Charging ................................................................................................................. 31
6.3
Service experience ........................................................................................................... 32
6.4
Conclusions ...................................................................................................................... 32
Comparison with alternative technologies ...........................................................................33
7.1
Lithium-ion battery .......................................................................................................... 33
7.2
Nickel metal hydride (NiMH) ........................................................................................... 35
7.3
Non-Battery energy sources ............................................................................................ 35
Conclusions .........................................................................................................................36
8.1
Lead crystal batteries ....................................................................................................... 36
8.2
Comparison with NiCad batteries .................................................................................... 36
8.3
Comparison with alternative technologies ...................................................................... 36
Recommendations ..............................................................................................................37
10. References ..........................................................................................................................37
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Figures
Figure 1 — Discharge characteristic of lead crystal and VRLA batteries ........................................... 22
Figure 2 — Effect of temperature on discharge capacity for a lead crystal battery (Betta Batteries)
............................................................................................................................................................ 23
Figure 3 — Self discharge characteristics of various lead-acid battery types (Deltec Power) .......... 23
Figure 4 — Cycle and float charge characteristics of lead crystal batteries (Betta Batteries) .......... 24
Figure 5 — Cycle life plots for lead crystal batteries (Betta Batteries).............................................. 25
Figure 6 — Summary cycle life plots for lead crystal batteries (Deltec Power) ................................ 25
Figure 7 — Float service life plots for lead crystal batteries (Betta Batteries) .................................. 26
Figure 8 — Summary float service life for lead crystal batteries (Deltec Power) .............................. 27
Figure 9 — Effect of Temperature on expected battery life.............................................................. 28
Tables
Table 1 — Comparison of energy density for lead crystal and VRLA batteries ................................. 22
Table 2 — Indicative prices for lead crystal and VRLA batteries ....................................................... 29
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Preface
This document is the second in a series of two, reporting on a review of lead crystal battery technology
delivered by Threepwood Consulting Ltd on behalf of the Energy Innovation Centre and its clients. Part 1 is
the Executive Summary and Part 2 (this document) is the Main Report.
1.
Introduction
The specification, operation and maintenance/replacement strategies of batteries used for network
applications by Utilities present a continuing problem. New battery technologies are being developed at an
increasing rate to meet the growing demands of other industries and there is an ongoing need to review
these developments to determine if they offer advantages for Utility use. Lead crystal batteries are one
such technology and the claims made by their proponents suggests that they could be applied to traditional
network applications to deliver enhanced service life and other financial and technical benefits. However,
experience with earlier developments, e.g. valve regulated lead-acid (VRLA) batteries, where performance
in service has fallen short of expectation shows caution is needed in accepting such claims. This current
project provides a staged approach to assessing the role that lead crystal batteries could play in Utility
applications. Stage 1 is reported here and is aimed at providing an understanding of lead crystal battery
technology compared with traditional batteries and identification of other competing battery technologies
that may be relevant for network applications now and in the future.
2.
Scope and Objectives
Carry out a desktop review of lead crystal battery technology, applications and perceived benefits. This
includes identification of any other competing battery technologies that may be relevant now and in the
near future. This encompasses the following activities.
1. Literature search on lead crystal batteries.
2. Compare technical specifications, features and benefits with traditional batteries (i.e. lead-acid and
nickel cadmium (NiCad).
3. Literature search on other competing battery technologies.
3.
Background
Effective battery life tends to be much shorter than many of the major components in a substation or
Utility plant room. UK electricity companies report a typical lifetime of 20+ years for Planté cell batteries
but for the more modern sealed VRLA batteries, currently in wide use, the life times are half of this or less.
New battery technologies are being developed at an increasing rate to meet the growing demands of other
industries for batteries that have high energy densities and improved capability for operation at higher
temperatures and the promise of longer lives. Much of the work in new battery types is aimed at providing
high energy density and regular deep cycling duty (e.g. energy storage, electric vehicle (EV) application,
etc.) where compact size and good cycling life is a priority. Such batteries are not necessarily optimised for
float duty. In parallel, developments continue for lead-acid batteries and, taking account of the huge
worldwide demand for lead-acid batteries, manufacturers continue to commit major resource to
developing improved lead-acid batteries. Some commentators suggest that such developments are likely
to prolong the use of lead-acid by many of industries for stationary battery applications for the foreseeable
future [1], in part because they are so well suited to long term float charge duty. The development and
introduction of the lead crystal battery can be viewed in this context and justifies consideration of them
against newer battery technologies.
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The lead crystal battery make use of a new advanced type of ‘Absorbed Glass Mat (AGM)’ material as a
separator, the electrolyte being completely absorbed and stored initially in the AGM. The electrolyte then
crystallizes during initial battery charge conditioning. Claims made by manufacturers are that the battery
performs in a similar manner to AGM VRLA lead-acid batteries but with additional benefits being: longer
service life; extreme temperature resistance; high current discharge performance and improved
environmental/safety impact. Since AGM VRLA batteries are successfully used for float applications, this
suggests applicability of lead crystal batteries for float applications. Manufacturers claim that the cells can
be discharged to zero volts and recover under normal charge conditions to 100% capacity within two cycles.
If substantiated, this would be advantageous for substation standby duty since prolonged outages, when
they do occur, can lead to premature failures for present generation lead-acid cells. The manufacturers
also claim the lead crystal technology is effective in overcoming loss of moisture, plate sulphation and loss
of active material leading to a battery life of 18 to 20 years, although other sources quote a more
conservative 12 years float life at 20°C. Notwithstanding, if a consistent service life of > 10 years can be
obtained then this is a worthwhile improvement over that achieved in service by present generation VRLA
batteries and would represent a significant advantage for lead crystal batteries.
The sections below examine the technology of the lead crystal battery against ‘traditional’ lead-acid
batteries in detail, followed by an assessment against NiCad batteries and other competing battery
technologies.
4.
Lead-acid battery technology
Although the basic electrochemistry and features of lead-acid battery are well known, it is useful to repeat
it here as a preface to a discussion of the lead crystal battery, which makes use of the same basic
electrochemical reactions occurring in the conventional lead-acid battery.
4.1 Electrochemical reaction
The basic lead-acid chemical reactions in a sulphuric acid electrolyte are as follows:
PbO2  Pb  2 H 2 SO4
arg e
disch




ch arg e
2 PbSO4  2 H 2 O
1
When the cell is recharged, the primary reaction that takes place is as shown in equation 1. Finely divided
particles of lead sulphate (PbSO4) are electrochemically converted to sponge lead (Pb) at the negative
electrode and lead dioxide (PbO2) is converted at the positive electrode by the charging source. The acid is
depleted during discharge and regenerated during recharge. For all lead-acid cells, the result of these
reactions is the production of hydrogen and oxygen gas and the potential for loss of water.
4.2 Cell design
Two designs are currently in common use.
4.2.1 Vented Lead-Acid (VLA) also referred to as flooded batteries
In VLA batteries the electrolyte is a liquid and ‘floods’ around the electrodes. In flooded cells, the oxygen
gas generated is released from the cell, and the hydrogen ion moves in the electrolyte to the negative plate
and is reduced there to hydrogen gas, which also leaves the cell. This results in water loss and de-ionised
water must be periodically added, a significant feature of a maintenance programme. Since the lead crystal
battery is a development of the VRLA technology, VLA types are not considered in detail in this report.
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4.2.2 Valve Regulated Lead-Acid (VRLA)
The basis of VRLA cell technology is to facilitate the oxygen recombination cycle whereby the oxygen and
hydrogen produced on float or overcharge are recombined to water. In VLA cells, only a very small amount
of the oxygen gas travels to the negative plate for recombination to water, because the solubility of oxygen
in water is very low. In VRLA cells two phases exist between positive and negative plates; a liquid one,
where the hydrogen ions can be transported and a gaseous one, where oxygen gas diffuses to the negative
plate. There, oxygen is reduced to water, which is far more likely than the reduction of hydrogen ions to
hydrogen gas. This formed water diffuses back. Only a small proportion of the hydrogen ions are reduced
to hydrogen gas, which leaves the cell through pressure sensitive release valves. In this way, the water loss
is virtually eliminated. The realization of the liquid phase, as well as the gaseous phase at the same place
between the positive and negative plates was the breakthrough for the VRLA cell.
There are two main classifications of present generation VRLA batteries: ‘gelled’ type where the electrolyte
has been immobilised by the addition of a gelling agent and ‘absorbed’ type where the electrolyte has been
immobilised in absorbent separators that are approximately 95% filled with liquid electrolyte.
There are performance differences between the AGM and gel type VRLA batteries, which in summary, are
that AGM technology has lower resistance due to its construction making it better for high discharge duty,
while gel technology has better thermal stability, cycle life and longer lifetime. The longer life for gel types
compared to AGM types basically results from the following factors.

Dry-out is a major failure mode for AGM batteries caused by shrinkage by losing water, resulting in
reduced contact with the electrode plates; therefore increasing the impedance and leading to thermal
run-away. The thermal run-away tendency is lower in gel batteries, because the recombination current
is restricted.

Gel batteries have lower oxygen recombination and this reduces the likelihood of premature sulphation
of the negative plates compared to AGM types.

During deep discharge or pole reversal, the microporous separator of gel batteries helps to prevent
short circuits by dendrite growth between the plates.

Cycle life is better in gel cells as they avoid acid stratification.
4.3 Electrode design
The reaction with the electrolyte takes place at the surface of the electrode and much development has
been carried out to optimise the electrode material for different applications, in summary:
• Pure lead, flat plate electrodes for standby long duration batteries with low current demands (original
Planté battery);
• Lead-Antimony used for cycling applications and heavy equipment starting batteries;
• Lead-Calcium (dominates the U.S. market) for flooded standby and VRLA designs;
• Lead-Selenium (dominates the European market) for flooded standby and cycling applications;
• Lead-Tin for VRLA.
In addition, a variety of electrode shapes are utilised; tubular, grid, multi-plate, paste construction, etc. to
increase the surface area in contact with the electrolyte, each designed with characteristics to meet specific
applications.
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4.4 Failure modes
4.4.1 Positive grid corrosion
The lead and lead alloys convert to lead oxide over time. Since the lead oxide is a bigger crystal than lead
metal alloy, the plate grows. After time the plates can grow sufficiently to distort a cell and cause it to fail.
The growth rate has been well documented and is taken into account when designing batteries. This tends
to be the main failure mode for VLA cells, assuming that regular maintenance and topping-up of the
electrolyte has been carried out over the life of the battery. Other failure modes tend to occur in VRLA
cells, particularly electrolyte ‘dry-out’ and shorting between electrodes (see below), before positive grid
corrosion is a factor and mean that they are unlikely to achieve the same design life as VLA types, as is
observed in practice.
4.4.2 Plate sulphation
Plate sulphation is the process of converting active plate material to inactive white lead sulphate and is a
problem in both VLA and VRLA cells. The sulphation leads to problems in the electrical path giving rise to
increased cell impedance and a reduction of discharge capability. Low charger voltage settings or
incomplete recharge after a discharge are the main causes of sulphation. When a battery is left in a
discharged state or for prolonged periods of storage, lead sulphate crystals begin to form acting as a barrier
to recharge and will prevent normal battery operation. Depending on the degree of sulphation, a battery
may be recovered from this condition by constant current charging at a higher voltage, with the current
limited to one tenth of the battery capacity for a maximum of 12 hours. The ‘forcing’ of current into a cell
tends to reverse the sulphation process. In extreme circumstances a cell may never fully recover from
sulphation and must therefore be replaced. An alternative approach for VLA cells is to attempt to remove
the sulphate build up by emptying, flushing and re-filling with electrolyte, before carrying out the
recharging procedure. Clearly this is not feasible with VRLA cells.
4.4.3 Sediment (shedding) build-up
Sediment build-up (shedding) is a function of the amount of cycling a battery endures. Shedding is the
sloughing off of active material from the plates, converting to white lead sulphate. Manufacturers allow
space at the bottom of the case to allow for a certain amount of sediment before it builds-up to the point
of shorting across the bottom of the plates rendering the cell useless. Shedding, in reasonable amounts, is
normal in all current lead-acid types.
In VLA cells action can be taken to prolong the cell/battery lifetime by removing the electrolyte, flushing
the sediment out and then refilling and recharging. Clearly in sealed VRLA cells such remedial action is not
possible.
4.4.4 Dry-out
This is one of the more common failure modes for VRLA cells (also called loss-of-compression at the
electrode plates of VRLA cells). It occurs due to high temperatures and is caused, for example, by excessive
ambient temperatures and over charging leading to elevated internal temperatures. At high internal
temperatures the pressure due to gas evolution can lead to venting through the pressure relief valve
removing the hydrogen and oxygen required to re-generate water. When sufficient electrolyte is vented,
the gel or AGM separator begin to lose contact with the electrode plates through shrinkage, increasing the
internal impedance and reducing battery capacity eventually leading to failure.
4.4.5 Thermal run-away
Thermal run-away is when battery internal components melt-down in a self-sustaining reaction. Normally,
this phenomenon is accompanied by float-charging current increase which hastens the onset of run-away.
It tends to occur more commonly in VRLA batteries because of the likelihood of cell dry-out and the
resulting increases in cell impedance exacerbating the heating due to the float current.
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The use of temperature-compensated chargers that reduce the charge current as the temperature
increases can minimise the chances of thermal run-away occurring, as well as taking steps to limit
temperature rise in the battery room or cabinet.
4.4.6 Minor and severe shorts
Minor (also called dendritic shorts) and severe short circuits are a significant failure mode for VRLA. Paste
lumps pushing through the gel or fiberglass mat and shorting out to the adjacent (opposite polarity) plate
typically cause severe shorts. Minor shorts, on the other hand, develop as the result of deep discharges.
When the specific gravity of the acid gets too low, the lead will dissolve into it. Since the liquid and the
dissolved lead are immobilised by the gel or glass fiberglass mat, when the battery is recharged, the lead
comes out of solution forming dendrites inside the gel or fiberglass mat. In some cases, the lead dendrites
short through to the other plate and can cause sudden catastrophic failures of the cell.
4.4.7 Terminal post leakage
Loss of electrolyte can occur due to leakage at the entry of the terminal posts to the case and can cause
loss of electrolyte. Often this is caused by cracking of the sealing compound in the lid around the pillars, or
deterioration of the rubber grommet in the pillar well. This loss of electrolyte can exacerbate the likelihood
of failure for VRLA batteries. Another possible problem is peroxidation on the positive pillar that can occur
if acid creeps up the pillar. Concentration cells occur on positive pillars when acid becomes trapped in the
sealing area, where the pillar passes through the lid, causing corrosion and reducing the cross-sectional
area of the pillar. If the concentration cell is severe then the whole pillar may be completely corroded away
in the lid seal.
5.
Lead crystal battery
5.1 Design and technology
In trying to assess the lead crystal battery technology, reliance has had to be placed on information
provided by the manufacturers and suppliers. Several UK and European suppliers have been identified (see
Appendix A) and all offer batteries manufactured by Betta Batteries1, the predominant and only
manufacturer identified during the writing of this report supplying the European market. There are a
number of Chinese manufacturers listed on the internet but their provenance could not be gauged by the
author and so information from them has not been included. A description of the lead crystal battery is
given below, obtained from the various suppliers, and which appear to be solely based on information
supplied by Betta Batteries. The author has been unable to find independent verification of the claims
made and others commentators note the lack of independent assessments. This may be explained by the
fact that Betta Batteries was founded in 2009 and so there is limited experience of the lead-acid battery in
service.
5.1.1 Description of the lead crystal battery design
The manufacturer’s literature states that the lead crystal battery consists of lead plates and an acidic
solution of SiO2 (silicon dioxide) as electrolyte. The SiO2 composite electrolyte is claimed to have been
developed by them to replace the traditional sulphuric acid electrolyte commonly used in acid (sic) and gel
batteries. During the initial charging cycles, the liquid composite electrolyte reacts with the lead plates.
This reaction causes the electrolyte to crystallise, forming a non-toxic white crystalline substance, leaving
no free liquid electrolyte in the battery. The crystallized electrolyte fixes to the active material on the
plates.
1
Head office: Betta Batteries Namibia, 40 Copper Street, Prosperta, Windhoek,
Namibia
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It is claimed that a unique blending technology containing a variety of inorganic salts and organic
substances, promotes a combined reaction that improves the reaction between the electrolyte and the
active material on the lead plates.
A new advanced type of micro porous high absorbent mat (AGM) material is claimed to be used as a
separator and which is claimed to have a much higher electrical conductivity, heat resistant and acid
resistant abilities than the standard AGM on the market. The crystallized electrolyte in combination with
the AGM can effectively protect the plates and prevent the active material from falling off during use.
The electrodes are grids cast from high purity lead calcium selenium alloy to ensure an extended life. The
positive grid alloy contains tin and calcium. This alloy is used to increase the plate resistance to corrosion
and improve deep cycle performance. A lead alloy combination in the negative grid plates is used to lower
internal resistance and improve the charge acceptance.
5.1.2 Assessment of the design
In view of the lack of independent verification of the claims made, the following assessment has been made
based on the author’s experience of battery systems and types.
In discussing the lead crystal battery, prior reference must be made to descriptions of ‘hybrid AGM gel’
VRLA batteries. Development of this battery began around 2000 and it utilises techniques for combining a
fiberglass mat separator of an AGM battery with a gel electrolyte. These have been reported in conference
papers [2, 3] and represent a development of present generation VRLA batteries. The concept seeks to
mate the advantages of the AGM and gel VRLA technologies into one battery type, viz. a battery having the
lower internal resistance of the AGM type combined with the better thermal stability, cycle life and longer
lifetime of the gel type. Clearly, the lead crystal battery2 design utilises the ‘hybrid AGM gel’ principle and
has extended the concept by developing a crystalline modification to the gel type electrolyte. As far as the
author is aware, the lead crystal battery is the first commercial product adopting the ‘hybrid AGM gel’
concept, albeit utilising a crystalline form of the gel electrolyte. Thus, the lead crystal battery can be seen
as an iterative development of VRLA technology and rather than a breakthrough.
In assessing the lead crystal battery design, the following comments can be made:

The use of dispersed SiO2 for electrolyte immobilisation
This is a well-established technique for creating the gel electrolyte in gel type VRLA batteries. As with
the lead crystal battery description, the gel structure in standard gel VRLA batteries is formed out of a
liquid solution within the cell to ensure intimate contact with the electrodes before creating the gel.
This allows all gaps to be filled between the separator and between the plates, no matter which
tolerance in thickness the plates have, both flat and tubular. Thus, the use of a dispersed SiO2 gel
electrolyte for the lead crystal is not new but the step of creating a crystalline structure is novel. The
process whereby the crystallized electrolyte fixes to the active material on the plates does appear to
represent a step forward. The claim that this increases battery life, particularly during cycling, by
effectively protecting the plates, in combination with the AGM, to prevent shedding of the active
material, does appear credible since shedding is a significant failure mode for VRLA cells.

Absorbent Glass Mat (AGM) design
A fiberglass mat between the plates is a well-established type of separator for AGM VRLA batteries.
2
United States Patent 4143216 in 1979 describes a design for what is referred to as a “lead crystal battery”. This
describes a storage cell in which the active mass on the positive electrode is a mixture of crystalline and an effective
amount of polycrystalline lead superoxide (PbO2). No further reference to this battery has been found. This does not
describe the lead crystal battery discussed in this report and has been disregarded for the purposes of this report.
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In a lead crystal battery the pore size and fibre diameters of the mat need to be optimised to allow
dispersion of the gel throughout the entire active material of the battery. Smaller pores and fibre
diameters are preferable to reduce problems with acid stratification and so it can be expected that a
development was needed to optimise the mat for the lead crystal battery. The SiO2 colloid size used to
create the gel would have been another variable. In this context the statement by the lead crystal
battery manufacturers’ that they have developed a new advanced type of micro porous high absorbent
mat (AGM) material is acceptable. The claim that this provides a much higher electrical conductivity,
heat resistance and acid resistance capability than the standard AGM on the market cannot be assessed
adequately without more information but it does line up with claims of the proponents of the ‘hybrid
AGM gel’ battery.

Electrode design
The use of high purity lead calcium selenium alloy for the grid electrodes is common practice for VRLA
batteries, as is the use of a tin/calcium alloy for the positive grid. This alloy is used to increase the plate
resistance to corrosion and improve deep cycle performance. A lead alloy combination in the negative
grid plates is used to lower internal resistance and improve the charge acceptance. Whilst
manufacturers will commend the virtues of their electrode technology, service experience from
standby applications indicates [4] that lead-calcium or lead-selenium is the best choice and either can
provide excellent service. Thus, the electrode design is not a novel feature of the lead crystal battery.
Whilst the lead crystal battery is not revolutionary, the manufacturer’s claims that it is superior to the
present generation VRLA battery have some credibility. The crystallized electrolyte state is said to provide
an enhancement of the channel for ion exchange and is effective in overcoming loss of moisture, plate
sulphation and loss of active material. In addition, improved temperature resistance and ability to recover
from discharge down to 0 V (100% depth of discharge) compared to VRLA batteries are claimed. The
potential validity of these claims is discussed below.

Reduced moisture loss
Gel type VRLA batteries are generally acknowledged to have longer life than AGM types, in part due to
the gel having a lower oxygen recombination. This leads to reduced recombination current that
reduces the tendency for thermal runway compared to AGM types. However, low recombination
efficiency can lead to increased water loss, a major factor in determining VRLA battery lifetime. This is
claimed to be addressed in the lead crystal battery by a composite electrolyte having various additives
that participate in the electrochemical reaction to inhibit the oxygen and hydrogen gas during the
charging cycle increasing the batteries gas recombination rate and reduces the water loss during and
after charging. To support this claim, the manufacturers published data of measured gas emission form
their lead crystal batteries. According to tests, performed by SGS (CE authorised testing facility), the
quantity of gas emitted during the chemical reaction phase (charging phase – discharge phase) by the
lead crystal batteries was only 1/200 of a normal lead-acid battery or AGM batteries. Other data
showed the lead crystal batteries only emitted 0.008 ml of gas during the charge cycle and none during
the discharge or storage cycles compared to figures of 0.037 ml and 0.034 ml of gas during all 3 cycles
for VLA and gel VRLA batteries respectively. This latter result does not appear to have been
independently validated but the taking the two results together shows a large improvement in favour
of the lead crystal battery.

Reduced plate sulphation
Lower oxygen recombination is known to reduce the depolarization of the negative electrode and the
premature sulphation of the negative plates. This supports the claim that during discharge the lead
sulphate is totally transformed back into active material, i.e. reduced sulphation, prolonging battery
service life. The promoters of the hybrid AGM gel battery [3] claim a very small decrease in positive
polarization (3 mV) compared to a conventional VRLA that would point to a decreased corrosion rate
and slightly favour increased life and this may be applicable to the lead crystal battery.
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Grid growth is another failure mode and is related to corrosion rate, and this will also favour the hybrid
AGM gel battery. It is not unreasonable to assign these advantages to the lead crystal battery.

Reduced loss of active material
As noted earlier, the crystallized electrolyte is claimed to ‘fix’ to the active material on the plates. The
claim that this increases battery life, particularly during cycling, by effectively protecting the plates, in
combination with the AGM, to prevent shedding of the active material, does appear credible since
shedding is a significant failure mode for VRLA cells.

Improved temperature resistance
The specified temperature range is -40 °C to +65 °C, claimed to be due to the low internal resistance
such that the internal temperature remains low when charged and discharged. The claim is somewhat
misleading because gel VRLA batteries are designed to operate over a range of -40 °C to +65 °C (e.g.
Exide Sonnenschein A range). The recommended temperature range for lead crystal battery is -5 °C to
+35 °C, which is similar to the typical range of 0 °C to + 40 °C that is quoted for gel VRLA batteries.
The manufacturer claims that cycling testing at +41 °C ambient temperature resulted in only 23% loss
of battery life for the lead crystal battery, although the test duration and cycle parameters are not
given. This compares favourably with expected values of around 60% reduction in expected life for
VRLA batteries at this temperature. One supplier states that the lead crystal battery can deliver more
than 85% of its rated capacity at -40 °C but this seems high compared to published data from Betta
Batteries (see Figure 2) , which indicates a capacity nearer 50% at this temperature. Nevertheless this
still compares favourably with gel VRLA batteries. Thus the claim of improved temperature resistance
has some validity.

Deep depth of discharge
The lead crystal battery is claimed to be capable of discharge down to 0 V (100% DOD) and being
restored to full rated capacity within two charges. Deep discharging of lead-acid batteries generally
leads to reduction in battery capacity and premature failure. This is mainly caused by a combination of
excessive sulphation that cannot be reversed by charging, increased loss of electrode material to
sustain the deep level of discharge and possible electrode disintegrate due to mechanical stresses that
arise from deep cycling. An explanation for the ability of the lead crystal to recover from 100%
discharge is not given but it may be due to the design causing less sulphation and the effect of the
crystalline electrolyte in mechanically protecting the electrodes. It is easy for users to test this
capability and there is anecdotal evidence available, particularly on “hobbyist” user forums, which
support the claim.
5.2 Performance specification
The battery characteristics discussed below are taken from Betta Batteries publically available data from
their website (www.leadcrystalbatteries.com) and supplemented by data from two of their suppliers;
Deltec Power Distributors (Pty) Ltd (www.deltacpower.co.za) and Axcom GmbH (www.axcom-batterytechnology.de). The battery range covers 2 V, 6 V and 12 V with capacities from 7.2 to 3000 Ah (10hr rate).
An example specification sheet for a 2 V, 100 Ah cell is given in Appendix B and is typical of all the batteries.
5.2.1 Energy density
The energy density of lead crystal batteries is better compared to ‘standard’ VRLA batteries but the
difference is small. Table 1 compares example data for the lead crystal battery and a typical VRLA battery
(Yuasa batteries data).
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Table 1 — Comparison of energy density for lead crystal and VRLA batteries
Nominal voltage (V)
Rated capacity (10 hr rate) (Ah)
Height (mm)
Length (mm)
Width(mm)
Weight (approx.) (kg)
Specific energy (Wh/kg)
2
1000
Lead crystal
330
475
175
61
32
12
100
VRLA
493
287
165
66
30
Lead crystal
220
330
172
31.5
38
VRLA
238
508
106
35
34
The higher energy density of the lead crystal battery offers some potential for reducing the size of a battery
installation but this is not assessed as providing a significant advantage for lead crystal batteries.
5.2.2 Discharge characteristics
Figure 1 compares published discharge curves at 25 °C for the lead crystal battery (Figure 1a) and a typical
VRLA battery (Figure 1b). It can be seen that the characteristics of the lead crystal battery are similar to
that for general VRLA batteries and indicate the lead crystal batteries are suitable as direct replacements
for VRLA batteries.
(a) Lead crystal battery (Betta Batteries)
(b) Typical VRLA battery (Yuasa)
Figure 1 — Discharge characteristic of lead crystal and VRLA batteries
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Figure 2 — Effect of temperature on discharge capacity for a lead crystal battery (Betta
Batteries)
As noted before, the lead crystal battery is quoted to have a wider operating range than ‘standard’ VRLA
batteries with improved capacity available at lower temperatures. Figure 2 reproduces a published plot of
temperature versus capacity.
5.2.3 Self discharge
Lead crystal batteries are claimed to have a low self discharge rate and can be stored for 2 years without
additional charging. A comparison plot published by one of the lead crystal battery suppliers to support
this claim is reproduced in Figure 3.
Figure 3 — Self discharge characteristics of various lead-acid battery types (Deltec Power)
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5.2.4 Charging characteristics
The manufacturer recommends lead crystal batteries should be charged using constant voltage for both
floating and cyclic charge applications. This agrees with the commonly held view that constant voltage
chargers with temperature compensation are the best choice for lead-acid batteries in general and VRLA
batteries in particular. As with VRLA batteries, the manufacturers of lead crystal batteries stress the need
for careful management of the charger and the charging regime. Thus, it would appear that the chargers
that are installed for use with VLA and VRLA batteries are suitable for lead crystal batteries, albeit with
possible adjustments to voltage and temperature compensation settings. The charging regime should be
comparable to that used for present generation VRLA batteries. Published charging curves at 25 °C for the
lead crystal battery under cycling and float conditions are reproduced in Figure 4. The characteristics are
similar to that for general VRLA batteries and again support the view that lead crystal batteries are suitable
as direct replacements for VRLA batteries with minimal changes needed to the chargers and charging
practice.
Figure 4 — Cycle and float charge characteristics of lead crystal batteries (Betta Batteries)
5.2.5 Battery lifetime
A major advantage claimed for lead crystal batteries is improved battery life compared to existing VRLA
types. The suppliers Deltec Power and Axcom GmbH quote headline figures for the battery life having a
float life of 18 to 20 years at 20 °C and a battery cycle life of 3 100 (charge and discharge) cycles depending
on depth of charge. A more detailed assessment of these claims is given below.
5.2.5.1 Cycle lifetime
The cycle life plots published by Betta Batteries are reproduced in Figure 5 and show the variation with
temperature and depth of discharge. This indicates that the headline figure of 3 100 cycles can be
misleading for when deep discharges are used. Deltec Power also publish a summary of the cycle
performance, reproduced in Figure 6, which better represents the data from Betta Batteries and is more
conservative and is likely to represent more accurately the cycle service life that can be expected.
Whatever the true figure, this cycling performance is adequate for standby duty on float charge that is
likely to be required by the clients of this contract.
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Figure 5 — Cycle life plots for lead crystal batteries (Betta Batteries)
Figure 6 — Summary cycle life plots for lead crystal batteries (Deltec Power)
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5.2.5.2 Float service life
This is likely to be of more interest to clients of this contract. The float service life plots published by Betta
Batteries are reproduced in Figure 7.
Figure 7 — Float service life plots for lead crystal batteries (Betta Batteries)
This data indicates that the headline figure of 18 to 20 years at 20 °C appears to be overstating the true
lifetime. In this context, both Axcom GmbH and Deltec power provide additional data which is more
conservative.

Axcom GmbH quotes a typical life span 12 years (i.e. the figure at 20 °C in Figure 7) in a table comparing
the characteristics of different battery type.
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
Deltec Power publishes a summary of useful float service life against temperature, reproduced in
Figure 8. This appears to be a realistic summary of the actual lifetime of lead crystal batteries in service
conditions and suggests a lower life at 20 °C than the 12 years quoted by Axcom GmbH.
Figure 8 — Summary float service life for lead crystal batteries (Deltec Power)
What is interesting in Figure 8 is that this range of lifetimes is typical of the service lifetime experience by
UK DNOs [confidential data available to the author] for existing VRLA batteries in float service where
lifetimes of 6 to 10 years are typical i.e. comparable to the values in Figure 8. Initial expectations for VRLA
had been over optimistic based on manufacturers’ quoted float lifetimes in excess of 10 years and being as
high as 15 to 18 years at 20 °C for gel VRLA batteries where only occasional discharges are encountered
(e.g. Exide Sonnenschein A range). Initially, users had not recognised the low tolerance of VRLA batteries to
poor temperature environment, charger choice and charging settings, resulting in replacement in 5 years or
less in some cases. Once these lessons had been learnt the performance of ‘second’ VRLA generation
installations has improved. The correct selection of a battery charger equipped with temperature
compensation, combined with regular checking of charger settings, is essential to delivering acceptable
battery life and 10 year life with acceptably low premature failure rates is seen as a realistic target.
In the light of this experience the claims for improved life of lead crystal batteries over existing VRLA
batteries in float service appear less convincing. It can be argued that the superior high temperature
performance of lead crystal batteries over existing VRLA batteries is a factor that could lead to them having
a longer service lifetime. Figure 9 compares the loss of life against temperature for the two types using
published data. Battery installations are rarely provided with temperature control of the battery
compartment and temperatures of 30 °C or more can be experienced in service, particularly for outdoor
equipment. As figure 9 demonstrates, this can have a dramatic effect on battery lifetime even if
experienced only for a few days in a year. The superior performance of the lead crystal battery at high
temperatures will help to mitigate this effect and would be expected to lead to longer life in service than
existing VRLA batteries.
A further factor to consider is the tendency for existing VRLA to suffer sudden premature failures in service,
which can be difficult to predict. Such a failure may only be discovered via (say) a failure to trip by a circuit
breaker.
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In the worst case, there are examples where this has caused catastrophic failure of a circuit breaker panel
or substation and reduction in such battery failures would be of significant benefit to users. At this stage
there is no published service experience, to know if this sudden premature failure mode is less likely in lead
crystal batteries but it is realistic to postulate that this may be the case. The capability of discharged down
to 0 V (100% DOD) and subsequent rapid restoration to full rated capacity may, in part, be due the
crystalline electrolyte providing mechanical protection to the electrode grid. Premature failure of VRLA
batteries can be due to damage and/or disintegration of the electrode grid and the mechanical protection
of the electrode grids within the lead crystal may assist in reducing premature failures.
Figure 9 — Effect of Temperature on expected battery life
In summary, it appears that introduction of the lead crystal battery may not provide a significant, or indeed
any, improvement in battery life in service compared to the best VRLA batteries currently in service. There
are grounds for expecting some improvement but the lead crystal does not appear to represent a major
breakthrough in this regard. This conclusion must be tempered by acknowledging that this is based on an
assessment of the design technology and not on evidence from long term service experience, since such
experience does not yet exist.
5.2.6 Maintenance
As might be expected, the maintenance requirements for lead crystal batteries are similar to existing VRLA
batteries and their introduction should not increase maintenance costs. One aspect to be considered is
that of regular impedance testing. This is used successfully by a number of operators to provide a check on
the performance and degradation of VRLA and VLA batteries in lieu of discharge testing. This provides a
cost effective means of detecting individual batteries in need of replacement and to monitor the overall
degradation rate of the population to establish optimum replacement strategies and has largely been a
successful maintenance strategy. It relies on assessing the impedance results against established criteria
from the users’ experience and widely available information worldwide to support the setting of criteria. It
can be expected that lead crystal batteries will have different impedance values and assessment criteria
from current battery populations and with the lack of operating experience it will be difficult to acquire this
information in a short time. This may present a difficulty in assessing their performance and establishing
service lifetimes. Users may need to return to regular discharge testing of lead crystal batteries in the
initial service period to gain confidence in their operational capabilities, which may add significantly to the
initial costs of maintaining and assessing the batteries.
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5.2.7 Service experience
As noted before, there is little information reporting lead crystal battery service experience. They have
found favour with ‘hobbyists’, particularly by boating users because of the attraction of the very deep
discharge capability and there is anecdotal information on internet user forums of such groups. The
feedback is generally favourable but as is the nature of such forums there is also a good deal of subjective
commenting and personal prejudices. Betta Batteries do publish customer feedback that is enthusiastic
regarding the benefits of their lead crystal batteries but perhaps this is not surprising.
Siemens have recently introduced lead crystal batteries in their range of uninterruptable power supply
solutions for use in traffic signal applications. They state that lead crystal technology provides excellent
charge performance, very high operating efficiency and enhanced operational life. They claim that they
offer an operational service lifetime of typically 6 to 12 years, compared to 2 to 4 years achievable with
standard lead-acid types and provide a charge time which is potentially faster than conventional lead-acid
batteries. It is unlikely that Siemens would jeopardise their high reputation without being confident of the
capabilities of lead crystal batteries. However, the figures for operational service lifetime appear to be
expectations rather than based on service experience.
5.2.8 Purchase costs
This has not been extensively investigated for stage 1 of the project. Advantage has been taken of the
decision by RS Components to supply Betta Batteries lead crystal batteries in the UK. Indicative example
prices are shown in Table 2 for lead crystal and ‘standard’ VRLA batteries in two sizes. Clearly, Utility
operators will be in a position to negotiate more favourable contract terms than the prices in Table 2 but
they do provide ‘ballpark’ values for comparison purposes.
Table 2 — Indicative prices for lead crystal and VRLA batteries
Nominal voltage (V)
Nominal capacity (Ah)
Price ea. 1 off
Price ea. 20 off
12
55
Lead crystal
(Betta Batteries)
£206.00
£191.58
VRLA
(Yuasa)
£168.83
£157.01
Lead crystal
(Betta Batteries)
£33.50
£31.16
12
100
AGM VRLA
(Yuasa)
£21.09
£19.61
AGM VRLA
(Panasonic)
£28.24
£26.26
The lead crystal battery price is higher than equivalent VRLA types but the premium is small when
considered in context of the lifetime costs for battery installations that include installation, maintenance,
disposal, etc. costs. Thus price is not seen as a significant barrier to adoption of lead crystal batteries.
5.3 Conclusions
The lead crystal battery has similarities to the technologies used in existing VRLA batteries, with the novel
concept being to utilise an ‘Absorbed Glass Mat (AGM)’ material as a separator combined with the use of a
gel electrolyte, which crystallises during initial charging the electrolyte, leaving no free liquid electrolyte in
the battery. The technology seeks to mate the advantages of the AGM and gel VRLA batteries into one
battery type, i.e. a battery having the lower internal resistance of the AGM type combined with the better
thermal stability, cycle life and longer lifetime of the gel type.
The manufacturer’s claims that it is superior to the present generation VRLA battery have some credibility.
From an assessment of the technology, it has been concluded that it is not unreasonable to accept the
manufacturer’s claims that crystallised electrolyte state provides an enhancement of the channel for ion
exchange and is effective in overcoming loss of moisture, plate sulphation and loss of active material.
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This can be seen as beneficial in enhancing reliability and increasing battery life as well as improved
temperature resistance and an ability to recover from discharge down to 0 V (100% depth of discharge)
compared to existing VRLA batteries, as claimed by the manufacturer.
However, using the manufacturer’s data the position is less clear regarding the claimed lifetime benefit
compared to existing VRLA batteries. Whilst the cycle life is likely to be significantly improved, this is of less
importance in standby duty and the cycling performance of existing VRLA batteries is generally adequate.
The float lifetime is of more relevance and the headline claims for lifetime are found to be optimistic, with
the figure of 18 to 20 years at 20 °C quoted in some literature appearing to overstate the true lifetime by
some margin. The manufacturer’s own specification sheets of plots of float service life against temperature
(Figure 7) indicate a lifetime of around 12 years at 20 °C falling away to 8 years at 40 °C. Only at 0 °C is the
figure shown as 18 years. Another published plot (Figure 8), described as a summary of float service life,
shows the range of lifetimes lower than this and presents values that are typical of the service lifetime
achieved with existing VRLA batteries. Thus the case for increased lifetimes for lead crystal batteries is not
well supported. This is considered somewhat surprising when the assessment of the technology suggested
that improved lifetimes could be expected. The only conclusion that can be drawn is that the float lifetime
of lead crystal batteries is likely to be comparable but may well be better than present generation VRLA
batteries. The actual position will not be determined until evidence from long term service experience is
obtained and which does not yet exist.
A review of the published data in relation to battery energy density, discharge characteristics, charging
characteristics, self-discharge rate and pricing concludes that the lead crystal battery can replace the
current VRLA battery installations on a like-for-like basis with only minor modifications to the existing
installations and battery chargers. Thus adoption of the lead crystal battery should be straightforward and
be carried out at relatively low installation costs.
6.
Comparison with NiCad batteries
NiCad batteries are in common use as standby batteries with full float operation3 as well as (typically)
transport duties where their good cycling capability and relatively high energy density is advantageous.
Vented/Flooded types and Semi-Sealed/Low Maintenance types fitted with low-pressure self-sealing valves
are available. Both employ the same electrochemical reactions but embody different design criteria and
performance characteristics. The vented types require topping up and in some cases a complete
electrolyte change and in this respect have similar maintenance requirements to VLA. Semi-sealed designs
with a large electrolyte reserve require no topping-up of the electrolyte and the only maintenance required
is an annual visual inspection and so are comparable to VRLA types in this respect.
6.1 NiCad technology
A fully charged Ni-Cd cell contains:
 Nickel oxide-hydroxide positive electrode plate;
 Cadmium negative electrode plate;
 Separator;
 Alkaline electrolyte (potassium hydroxide).
3
Hermetically sealed NiCad batteries of the type used in portable applications are not suitable for float charging
applications and are not considered in this report.
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The basic reaction in a potassium hydroxide (alkaline) electrolyte is:
2 NiO(OH )  Cd  2 H 2 0
Positive
electrode
arg e
Disch




Ch arg e
Negative
electrode
2 Ni(OH ) 2  Cd (OH ) 2
Positive
electrode
2
Negative
electrode
There is much use world-wide of NiCad batteries for power system duties with many claims of superiority
over lead-acid types. The main advantages claimed for NiCad batteries are:
• More robust than lead-acid types;
• Risk of sudden catastrophic failure is considerably lower than VRLA types;
• Manufacturers claim a design life of 20 years, but service experience in power utilities shows this to be
typically more like 8 – 10 years i.e. similar to VRLA;
• More resistant to high ambient temperatures than lead-acid types. The rate of aging is about 20%
reduction in life for 10°C increase in temperature. This compares to lead acid batteries, where the rate
of aging can be as high as 50% for each 10°C rise in temperature. However, it may be difficult to justify
their use on this basis alone unless the temperature conditions are particularly unfavourable;
• Better high current output capability than lead-acid types. A NiCad battery can supply up to 3 times as
much current in proportion to their nominal capacity compared to lead-acid batteries. This clearly is a
major advantage in (say) transport situations. It may be an advantage in small utility situations with
low continuous drain but intermittent higher current demand (e.g. circuit breaker tripping) by allowing
a smaller battery capacity installation than would be required with a lead-acid battery. However, other
techniques can used (e.g. ultracapacitors) in combination with VRLA batteries to achieve this at lower
cost.
• NiCad batteries continue to provide high design current output capability over their whole lifetime
unlike lead-acid where this degrades with age. This again can influence the initial sizing of the battery;
• Like lead crystal batteries, NiCad batteries can be restored to near full capacity after being discharged
to zero volts.
The main disadvantages compared to lead-acid batteries are:
• Relatively high initial purchase cost;
• More complex charging requirements;
• Higher disposal costs at end of life due to restrictions placed on cadmium disposal;
• Special shipping/handling requirements due to hazardous nature of materials used;
• Vented/flooded designs have comparable maintenance requirements to VLA because of the need to
replace electrolyte losses during normal operation;
• Vented/flooded designs have ventilation requirements required to disperse gases produced during
normal operation similar to VLA.
6.2 NiCad Charging
User experience shows correct charging methods are one of the most important factors in obtaining good
performance and lifetime from NiCad batteries, which require more attention to the charging procedure
compared to lead-acid batteries. In NiCad battery installations, it is particularly important that operations
staff are aware of the correct practice in their day-to-day maintenance activities of battery chargers if the
full performance and lifetime expected from NiCad batteries is to be achieved in practice. Poor charging
practice can be a significant factor in shortening the useful life of a NiCad battery.
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Constant voltage chargers are commonly used for standby duty. The float current should be limited to
prevent damaging the battery. Typical figures are 120 –150mA per 100Ah nominal capacity with a cell
voltage of 1.4 – 1.45 V/cell but manufacturers’ figures should be used. Since this charge rate is low, there
may be a requirement for the standby battery to be recharged more rapidly after a discharge. Automatic
boost chargers are available that provide a two-step float voltage characteristic to increase charge rate in
the initial stages when the mains voltage is reconnected. Use of a set voltage above the manufacturers’
specification should be avoided as overcharging generates excess gas leading to rapid water depletion and
shortens their service life and regular attention to the battery settings and performance is a prerequisite
for NiCad battery installations.
Whatever charging method is used, an equalisation charge is recommended initially and every 3 to 6
months with a charging current equivalent to the 5h charging rate for 15h depending on the characteristic
of the charger to ensure full nominal capacity. This arises because each cell in a battery has its own
characteristics, each requiring a slightly different amount of charge.
The temperature in a battery room can have a significant effect on the level of charge in a NiCad battery
due in part to the negative temperature coefficient characteristic, whereby as the cell temperature rises,
the internal resistance falls. This can pose charging problems, particularly with the relatively simple
charging systems. Charging at higher temperatures causes a NiCad battery to take a reduced charge and
the capacity can be significantly lower than expected from the design calculations. This may prejudice any
subsequent standby duty. Similarly, a NiCad battery charged at room temperature will lose capacity if used
at a higher temperature, again prejudicing the standby duty at that temperature.
In summary, the cost of maintaining a satisfactory charging regime can be a significant additional cost
compared to lead-acid batteries.
6.3 Service experience
NiCad batteries have not found widespread use in the UK electricity industry. The experience by UK DNOs
[confidential data available to the author] for NiCad batteries in float service indicates that service lifetimes
of 8 to 12 years are typical and is significantly less that the manufacturers’ figures of a design life of 20
years and is not significantly better than for VRLA batteries. There is much use world-wide of NiCad
batteries for power system duties with many claims of superiority over lead-acid types. However, the few
reports of actual in-service performance do not always support the lifetime claims. For example, NiCad
batteries were used to replace Planté batteries for an ESKOM power station application in South Africa.
The design expectation was a lifetime of 20 years. The actual life span has been 12 years and ESKOM
decided to consider alternative battery technologies.
6.4 Conclusions
NiCad batteries have not found widespread use in the UK electricity industry, caused by a combination of
factors:
• High initial purchase costs;
• Lifetimes only comparable to VRLA batteries;
• Maintenance and charging regime costs higher than VRLA batteries;
• High disposal costs compared to lead-acid batteries.
The cost disadvantage and moderate service lifetime appear to have been a disincentive for UK electricity
companies to adopt NiCad batteries to date.
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This has outweighed the benefits of mechanical robustness, reduced risk of sudden catastrophic failure,
resistance to high operating temperature and good high current output capability. When viewed in the
context of the lead crystal battery, it is difficult to justify adoption of NiCad batteries at this time.
7.
Comparison with alternative technologies
There is much development in the field of battery technologies stimulated particularly by demand in
transport (e.g. electric vehicles) and energy storage for renewable energy support applications. The most
prominent of these are the lithium-ion batteries, which may find a role in float standby duties. Other
possible contenders are reviewed in this section.
7.1 Lithium-ion battery
After well reported initial problems, recent developments have made the Lithium-ion battery viable and it
is in wide use for small appliance, electric/hybrid vehicles and beginning to be utilised for telecoms
uninterruptible power systems UPS and electric energy storage applications. A major advantage over other
battery technologies is the high energy density, which is currently around 6-8 times that of a lead-acid
battery, and excellent deep cycling capability. The complex electrochemistry, materials science and design
technology means that there is a vast array of information available and it is beyond the scope of this
report to cover this in detail. In summary, there are 6 main lithium-ion battery technologies:

Lithium Cobalt Oxide(LiCoO2)
Lithium Cobalt Oxide has high specific energy making it the popular choice for cell phones, laptops and
digital cameras. The main drawbacks are relatively short life span, low thermal stability and limited
load capabilities (specific power).

Lithium Manganese Oxide (LiMn2O4)
Lithium Manganese Oxide has improved thermal stability and enhanced safety compared to Lithiumcobalt but the cycle and service life is limited. Lithium-manganese is used for power tools, medical
instruments, as well as EVs.

Lithium Nickel Manganese Cobalt Oxide (LiNiMnCoO2 or NMC)
Leading battery manufacturers focus on a cathode combination of nickel-manganese-cobalt (NMC). It
is similar to Lithium Manganese and can be tailored for high specific energy or high specific power, but
not both. They are used for E-bikes, medical devices, EVs and industrial applications.

Lithium Iron Phosphate(LiFePO4)
Lithium phosphate offers good electrochemical performance with low resistance. The key benefits are
high current rating and long cycle life combined with good thermal stability, enhanced safety and
tolerance if abused. Lithium-phosphate is often used to replace the lead acid starter battery and other
portable and stationary applications needing high load currents and endurance.

Lithium Nickel Cobalt Aluminium Oxide (LiNiCoAlO2 or NCA)
Lithium Nickel Cobalt Aluminium Oxide battery shares similarity with NMC and has high energy and
power densities, as well as good life span, making the NCA a candidate for EV powertrains (e.g. TESLA
vehicles) as well as medical devices and industrial applications. Their high cost and marginal safety are
negative attributes.

Lithium Titanate (Li4Ti5O12)
Lithium titanate replaces the graphite in the anode of a typical lithium-ion battery. They can be fastcharged and can deliver a high discharge current of 10 times the rated capacity with an excellent
cycling performance and has excellent low-temperature discharge characteristics. Of the Li-ion
batteries, Lithium titanate is rated as one of the safest and having the longest life span. However, the
battery is expensive and at 65Wh/kg the specific energy is low being comparable to that of NiCad cells.
Typical uses are electric powertrains (e.g. Mitsubishi and Honda) and for UPS applications, where safety
and cycle life can be more important than capacity alone.
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To the list must be added the Lithium-polymer types. Their main difference is the type of electrolyte used
with modern Li-polymer battery using gelled electrolyte. Lithium polymer can be built onto many systems
of the above Li-ion types and so is not considered unique battery chemistry. Most Lithium-polymer packs
are for the consumer market and are based on Lithium cobalt.
Energy density is not a major factor in substations and it is difficult to justify lithium-ion on this basis
coupled with the present very high price. However, the high temperature operation is good, with very little
difference in the rate of ageing at 60 °C compared to 25 °C, and is a significant factor in favour of them
since the relatively low life of VRLA batteries is in part due to their poor tolerance to high ambient
temperatures that can be experienced in service. To date, most testing of Lithium-ion batteries has been
directed towards cyclic operation, but work continues to characterise them for continuous float charging
duty, as required in standby applications. Early indications suggest that a float life of 15 years or more [5] is
achievable with the current generation of lithium-ion batteries. To this must be added the fact that they
are virtually maintenance free; an attribute clearly of great importance to EV applications, where users
expect a “fit and forget” approach to the battery. This same attribute is also desirable in utility standby
applications and appears to be an achievable attribute. Given the huge investment in lithium-ion
technology, it appears inevitable that lithium-ion batteries will come into contention for utility standby
applications. Indeed, Lithium-ion batteries for UPS batteries are already commercially available (e.g. Li-ion
Evolion® from Saft) that claim compact, low weight sealed batteries requiring no maintenance and float
lifetimes of 20 years at 20 °C and greater than 10 years at 40 °C.
A factor to be considered is that the charging characteristics of lithium-ion batteries are more complex than
lead-acid and NiCad batteries. Overcharging is not beneficial to charge capacity and can lead to destruction
of the battery. Recent high profile incidents with lithium-ion batteries are testament to what can occur
with inappropriate practice. Ideally, lithium-ion battery charging systems should incorporate electronic
controls, also referred to as a Battery Management System (BMS), to manage the lithium-ion battery
performance and also ensure safe operation [6] leading to a further cost penalty. Whilst, the constant
voltage charging systems commonly used in utility float operation can be adapted for use with lithium-ion
batteries, compromises in battery performance and greater attention to battery charger settings and
maintenance checks would have to be accepted. The charging voltage must be at a set and maintained at a
specified constant level and below a specified maximum. This means that the temperature equalisation
setting in a charger may have to be disabled. In addition, the float voltage used for maintaining 100% stateof-charge may be too high for permanent operation of connected loads because of the different voltage
rating of lithium-ion cells compared to lead-acid and NiCad cells [7]. This may mean a re-design of
connected devices to operate at a different voltage or accepting that the in-service state-of-charge is <
100%, requiring the installation of additional nominal lithium-ion battery capacity to compensate. In both
cases there is a cost penalty. These present new variables that the battery end user must consider when
evaluating and consideration of adoption of lithium-ion batteries.
In summary, lithium-ion batteries can be expected to offer attractive benefits in a number of standby
market sectors and these will be fully developed and quantified in the near future. It appears inevitable
that lithium-ion batteries will come into contention for utility standby applications and indeed commercial
batteries are currently available. However, the onus will be on users to make a careful and thorough
evaluation of the suitability of a particular Lithium-ion product for their application, and whether the
manufacturer is likely to remain in business over the coming years to provide service and spare parts for
their batteries.
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7.2 Nickel metal hydride (NiMH)
These are chemically similar to NiCad but have a higher energy density. This is a major factor for electric
vehicle applications but of much less importance to utility standby duties. Large capacity NiMH batteries
are now in production for electric vehicles. Although NiMH batteries are maintenance free with respect to
the electrolyte this advantage is offset by increased intolerance to temperature extremes compared to
NiCad. Since high temperature operation is one of the factors in considering batteries, this counts against
NiMH along with the higher cost compared to NiCad. Clearly future developments will improve this
situation but it appears unlikely that NiMH batteries will be preferred over NiCad batteries in the
foreseeable future.
7.3 Non-Battery energy sources
There are a number of energy sources such as ultracapacitors, flywheels and fuel cells, which show some
potential for standby duty.
7.3.1 Ultracapacitors
In the UK electricity industry, traditional electrolytic capacitors have seen some use as replacement to
battery switch tripping units for several years now. These have proved very reliable. The use of
ultracapacitors, which are technically superior to electrolytic capacitors, in this and similar roles to
substitute for batteries, seems a logical development. A commercial unit is currently available for use
within overhead auto-reclosers, as an alternative to lithium batteries, but the author is not aware of
whether any units are actually in service. They can be seen to have a role in float standby situations by
reducing the battery capacity to support the constant Ah duty, with the ultracapacitor handling the
transient switching duty. However, this role does remove the need for a battery for the constant drain
standby applications.
7.3.2 Flywheels
Flywheels have been deployed in energy storage roles in both the electricity and transport industries. They
could be developed for standby duty to replace batteries but the author is not aware of any active
development in this idea.
7.3.3 Fuel cells
As might be expected, hydrogen fuel cells are attracting attention since they will continue to provide power
indefinitely, as long as hydrogen fuel is available. However, they do not provide an instantaneous response
that is required in UPS and float standby duties, requiring time to warm up before delivering full output.
Thus, it may be necessary to operate them as hybrid systems in combination with a small capacity battery
or ultracapacitor to provide current during the warm up time of the fuel cell. At this time, they are
untested in this application.
7.3.4 Zinc air regenerative cells
These are being developed for large capacity energy storage purposes and some utilities are exploring their
use in this role. Currently, such batteries are complex, high cost devices but as development continues
some commentators suggest that they offer promise as a stand-alone system suitable for standby battery
applications. Therefore this option may come to the fore, in the near future, but at this stage do not
appear to be a viable option.
7.3.5 Pnu DC power source
This is a compressed air source driving a proven scroll expander connected to a generator to provide DC
power, marketed by Energetix, the pneumatic generator coming into operation on loss of mains supply in
the same manner as a battery. Outputs of 12/24/48/54/110/120V dc, up to 5kW are available. It is
designed to replace standby battery and battery charger installations. A major advantage is the capability
of an indefinitely long run time, limited only by the compressed air capacity.
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The product is in limited use in telecoms and IT industries and National grid are conducting a trial at a
275kV substation. This is a commercial product that is available off-the-shelf and does appear to offer a
viable alternative to the use of batteries for standby duty. Whilst it is not within the scope of this current
project, the clients of this contract may wish to pursue further in a different project.
8.
Conclusions
This project has sought to assess the role of lead crystal batteries, in particular, and new battery
technologies, in general, to address the issue of disadvantages and limitations arising from the use of lead
acid and NiCad batteries in traditional UPS and float standby applications. The methodology has been to
carry out a literature survey to understand the new lead crystal battery technology (specification and
features) compared with traditional batteries and to identify other competing battery technologies that
may be relevant for network applications now and in the future.
8.1 Lead crystal batteries
The overall conclusions are that:
 Based on an assessment of the design technology, the manufacturer’s claims that it is superior to the
present generation VRLA battery have some credibility.
 However, using manufacturer’s published data the case for increased service lifetimes for lead crystal
batteries compared to existing VRLA batteries is not well supported.
o Whilst the cycle life is likely to be significantly improved, this is of less importance in standby duty
in the UK and the cycling performance of existing VRLA batteries is, in general, adequate.
o The float lifetime is of more relevance and the headline claims for lifetimes of 18 to 20 years at
20 °C quoted in some literature are found to be optimistic. The manufacturer’s specification sheets
of float service life against temperature indicate that a lifetime of 18 years is expected only at 0 °C,
being 12 years at 20 °C and 8 years at 40 °C. Other published plots of expected service float service
life, show the range of lifetimes lower than this and the values given are typical of the service
lifetime achieved by UK DNOs for existing VRLA batteries. This is considered somewhat surprising
when the assessment of the technology suggested that improved lifetime might be expected.
 Overall, the best assessment is that the float lifetime of lead crystal batteries can reasonably expected
to be as good and potentially may be better than the VRLA batteries they would replace. The actual
position will not be determined until evidence from long term service experience is obtained and which
does not yet exist.
8.2 Comparison with NiCad batteries
It is concluded that there is not a strong case for adoption of NiCad batteries either as a policy of
replacement for VRLA batteries or as an alternative to the introduction of lead crystal batteries.
8.3 Comparison with alternative technologies
The current viable options appear to be:


Lithium-ion batteries
Lithium-ion batteries can be expected to offer attractive benefits in a number of standby market
sectors and these will be fully developed and quantified in the near future. It appears inevitable that
lithium-ion batteries will come into contention for utility standby applications and indeed commercial
batteries are currently available. However, the onus will be on users to make a careful and thorough
evaluation of the suitability of a particular Lithium-ion product for their application.
Pnu DC power source
This is a commercial product that is available off-the-shelf.
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9.
Recommendations

The current project should continue to completion as the lead crystal battery does appear to offer
some tangible benefits. In the long term, a trial of lead crystal batteries is seen as a sensible step. It
would be reasonable, at least as part of a trial, to substitute lead crystal batteries in place of VRLA
batteries in some in-service locations where VRLA battery lifetimes are known to be low (e.g. 5 years or
less). The like-for-like replacement appears straightforward and the operational risk is perceived to be
low since the performance of the lead crystal batteries can reasonably be expected to be as good as
and potentially better than the VRLA batteries being replaced.

The clients should consider projects to assess the viability of introduction of lithium-ion batteries and
the Pnu DC Power Source for float standby duty.
10. References
[1] How automotive battery developments will influence future stationary batteries. D Cox. Battcon
Proceedings 2009.
[2] VRLA battery with AGM-gel hybrid for superior performance. S S Misra, S L Mraz, J, Dillon & D B
Swanson. Telecommunications Energy Conference, 2003. INTELEC '03.
[3] Hybrid advanced GEL VRLA batteries. T O’Sullivan. Battcon Proceedings 2008.
[4] Lead-antimony, Lead -calcium, Lead -selenium, VRLA, NI-CD. What’s in a name? M S Clark. Battcon
Proceedings 2009.
[5] Long-term field experience with a stationary Lithium-ion battery in a substation application. M Leksell,
P Krohn, B Nygren & Trond Beyer. Battcon Proceedings 2015.
[6] Commercial Lithium ion reserve power systems. J Anderson, J Frankhouser & D Boyer. Battcon
Proceedings 2010.
[7] Game changer? The potential impact of vehicle electrification on the stationary battery world.
J McDowall Battcon Proceedings 2012.
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APPENDIX A
UK and European Suppliers of Lead Crystal Batteries
Lead Crystal Batteries
Dovecote Manor Barns
Main Street
Snarestone
Leicester
Leicestershire
United Kingdom
DE12 7DB
Tel: 01530 274680
Website: lead-crystalbatteries.co.uk
Harland Simon UPS Limited
Bond Avenue
Bletchley
Milton Keynes
MK1 1TJ
Tel: +44 1908 565656
Fax: +44 1908 568400
Website: harlandsimonups.com
Head Office Elfa United Kingdom:
Elfa Elementenfabriek Ltd.
Burrough Court
Burrough-on-the-Hill
Melton Mowbray
Leicestershire
LE14 2QS
Tel: +44 (0) 1664 250025
Website: elfa.com
RS Components Ltd
Birchington Road
Corby
Northants
NN17 9RS, UK
Tel: 08457 201201
Website: rs-components.com
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APPENDIX B
Example Specification Sheet - Betta Batteries 2 V, 100 Ah Cell
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Document History
Version
1.0
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Date
Amendment
Issued by
Authorised by
First issue
Richard Parke
Senior Consultant
Gary Eastwood
Executive Director
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