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チペワ CHIPPEWA OCM305001A BLACK 4 PLAIN TOE ワークブーツ

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Innovation in Lithium Batteries
LiFePO4 Power Battery: Faster charging and safer performance
It is well established that small capacity Li-ion (polymer) batteries containing lithium cobalt oxide
(LiCoO2) offer a genuinely viable option for electronics and digital applications. However, lithium cobalt
oxide (LiCoO2) is very expensive and un-safe for large capacity Li-ion Batteries. Recently lithium iron
phosphate (LiFePO4) has been becoming "best-choice" materials in commercial Li-ion (polymer) Batteries
for large capacity and high power applications, such as power tools, e-wheel chairs, e-bikes, e-cars and ebuses. A LiFePO4 battery has hybrid characters: as safe as lead-acid batteries with lower environmental
impact, and as powerful as lithium ion cells. The advantages of large format Li-ion (polymer) batteries
containing lithium iron phosphate (LiFePO4) are listed as below:
1. Fast charging:
During the charging process, a conventional Li-ion Battery containing lithium cobalt oxide (LiCoO2)
needs two steps to be fully charged: step 1 is using constant current (CC) to get 60% State of Charge
(SOC); step 2 takes place when charge voltage reaches
4.2V, upper limit of charging voltage, turning from CC to
constant voltage (CV) while the charging current is taping
down. The step 1 (60%SOC) needs two hours and the
step 2 (40%SOC) needs another two hours. LiFePO4
battery can be charged by only one step of CC to reach
95%SOC or be charged by CC+CV to get 100%SOC.
The total charging time will be two hours.
2. Large overcharge tolerance and safer performance
A LiCoO2 battery has a very narrow overcharge tolerance, about 0.1V over 4.2V of charging voltage
plateau and upper limit of charge voltage. Continuous charging over 4.3V would either damage the battery
performance, such as cycle life, or result in firing and explosion. A LiFePO4 battery has a much wider
overcharge tolerance of about 0.7V from its charging voltage plateau 3.4V. Exothermic heat of chemical
reaction with electrolyte measured by DSC after
overcharge is only 90J/g for LiFePO4 verse 1600J/g
for LiCoO2 . The more is the exothermic heat, the
larger energy heating up the battery in its abusive
condition, the more chance of fire or explosion. A
LiFePO4 battery would be overcharged up to 30V
without protection circuit board. It is suitable for large
capacity and high power applications. From viewpoint
of large overcharge tolerance and safety
performance, a LiFePO4 battery is similar to lead-acid
battery.
3. Self balance
Like lead-acid batteries, a number of LiFePO4 cells in a
battery pack in series connection would balance each other
during charging process, due to large overcharge tolerance.
This self balance character can allow 10% difference between
cells for both voltage and capacity inconsistency.
4. Longer cycle life
In comparison with LiCoO2 battery which has a cycle life of approximately 400 cycles, LiFePO4 battery
extends its cycle life up to 2000 cycles.
5. Simplifying battery management system (BMS) and battery charger
Large overcharge tolerance and self-balance characters of LiFePO4 batteries simplify battery protection
and balance circuit boards, lowering their cost. One step charging processes allows simpler conventional
power supply to charge LiFePO4 batteries, instead of expensive the more expensive Li-ion battery
chargers.
6. High temperature performance
It is detrimental to have a LiCoO2 battery working at elevated temperatures, such as 60degrees
Celsius. In fact, anything above 25 degrees can be harmful to your battery. However, a LiFePO4 battery
runs better at elevated temperatures, offering 10% more capacity, due to higher lithium ionic conductivity.
Comparison data among various Lithium base batteries:
C-LiFePO4
LiCoO2
LiMn2O4
Li(NiCo)O2
Acceptable
Not stable, dangerous
CYCLE LIFE
Best among all
the listed
Acceptable
groups
Unacceptable
Acceptable
POWER WEIGHT
DENSITY
Acceptable
Good
Acceptable
Best
LONG TERM COST
Excellent, most
High
economic
Acceptable
High
WORKING TEMP.
Excellent
45C-70C
Excellent,
SAFETY AND
ENVIRONMENTAL
CONCERNS
Not stable,
Best among all
dangerous
existing
batteries
1.
COMMENTS
-
Decayed
Decayed beyond
extremely fast
-20C ¨C 55C
over 50C
Decayed extremely fast
below -20C and above
55C
Lead Acid batteries are lower in cost and safely
acceptable; however, they are extremely toxic, worse
for the environment, have short cycle life, are heavy in
weight, and therefore, we don't consider it as a viable
group for comparison.
2.
Nickel Hydride batteries have low Power Weight
Density, they decay faster under high temperatures,
suffer worse memory effect, and are not considered
suitable for high output usage.
3.
The C-coated Lithium Iron Phosphate Battery has
been proven as the most environmental friendly
battery. It is the safest and most suitable for high
output usage on electric bikes, and also the best value
for its cycle life.
Source: www.goldenmotor.com
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