Electric cars battery check-up 2010

Post date: Apr 26, 2010 5:24:44 PM

Research study says EVs have a tough road ahead

Battery explainer Li-ion, LiFePO4

The proper name is lithium-iron-phosphate often referred to as

LiFePO4. It is a lithium-ion battery but is made with iron and

phosphate.

Li-PO chemistry is good for 1400 cycles before hitting the 80% threshold.

With daily charging, that battery is good for about 4-5 years before the OEM

would consider the battery "unsatisfactory". when you only deplete your

pack 20% you will get more cycles out of it. That is why the Volt estimates

10 year life span as it will deplete to 50% maximum.

Range: 140kmls

For example, a 35kWh pack good for 1400 cycles, it is good for ~49MWh of

discharge over its lifetime. If the 1400 cycle pack can travel 100 miles at

100% utilization, it is good for roughly ~140k miles.

Keep charge level near 50%

The sweet spot is to keep the charge level near the 50% range for the

longest period of time in the life of a battery (50% is near the optimal

level to store lithium batteries with little loss of capacity)

Electric cars

To power larger devices, such as electric cars, connecting many small

batteries in a parallel circuit is more efficient than connecting a single

large battery.

Shelf life

At a 100% charge level, a typical Li-ion laptop battery that is full most

of the time at 25 °C or 77 °F will irreversibly lose approximately 20%

capacity per year. However, a battery in a poorly ventilated laptop may

be subject to prolonged exposure to higher temperatures, which will

shorten its life. Different storage temperatures produce different loss

results: 6% loss at 0 °C (32 °F), 20% at 25 °C (77 °F), and 35% at

40 °C (104 °F). When stored at 40%–60% charge level, the capacity loss

is reduced to 2%, 4%, 15% at 0, 25 and 40 degrees Celsiusrespectively

Laptop batteries for cars ?

"And it points out that while li-ion batteries used in consumer electronics

currently cost between $250 and 400/kWh..."

I wouldn't so quickly dismiss consumer li-ion batteries as a viable type of battery

for automotive applications. After all, the poster boy for BEVs, Tesla, is still using

these batteries and will continue to. Cycle life is about half of the cells most

automakers are using, but you can make up for it by offering a car with twice the

maximum range (twice the battery size). For example: 1000 cycles in the Volt

battery, 80 miles in 100% utilization = 80k life (ignoring for the moment, the

impact of the 50% buffer). 500 cycles for consumer batteries, means you need

160 miles of range at 100% utilization (twice the size 16kWh*2 = 32kWh)

to get the same 80k life.