Comments on: USABC Battery Contractor Comparison

By: GM-VOLT : Chevy Volt Concept Site » Compact Power CEO Describes How Their New Chevy Volt Cells are Better

Wed, 05 Dec 2007 14:51:12 +0000

[...] For more on how some battery companies lithium-ion cells compare with one another, see this post: (LINK) [...]

By: AES

AES — Mon, 29 Oct 2007 07:50:20 +0000

[quote comment="12537"]The motor is 120KW; to generate that power with a 160kg pack you would only need a power density of 750w/kg.[/quote]

Very true. However, the more powerful the cells are, the lower the discharge rate needs to be to achieve 120kW. The lower the discharge rate, the less strain it is on the battery, and the longer the lifespan.

By: Mike756

Mike756 — Mon, 29 Oct 2007 01:51:50 +0000

Having specific power less than 3000W/kg doesn’t seem like a problem. The energy density is much more limiting, but still very good. Assuming 100wh/kg, you would need 160kg battery for the 16kwh pack. The motor is 120KW; to generate that power with a 160kg pack you would only need a power density of 750w/kg.

By: AES

AES — Sun, 28 Oct 2007 21:53:51 +0000

[quote comment="12482"]Until they start delivering the Volt or go public with specifics on each cell then it is all guess work.[/quote]

Yes but given that the automotive A123 cells are made with the same fundamental chemistry, you can at least do some EDUCATED guesswork.

For example, part of the power density of the power tool (M1) cells is that there is a short path length from the electrode to the current collector. If you were to thicken the electrodes, the path from electrode to current collector is longer, and there is more electrical resistance in the way. This reduces the power, but would also increase the amount of energy storage.

Given the premium put on weight reduction and energy storage, the Volt will probably make this compromise.

In other words, expect a specific power lower than 3,000W (~4 horsepower) per kilogram of batteries, but do expect specific energy closer to LiFePO4’s theoretical max energy storage of ~130Wh/kg.

By: Van

Van — Sun, 28 Oct 2007 18:25:27 +0000

Guesswork sounds dismissive, how about feasibility estimate.

By: SteveF

SteveF — Sun, 28 Oct 2007 13:31:56 +0000

As I recall from previous interviews with A123 and maybe others, the battery cells that will be delivered for the Volt is not available on any of the public web sites. Until they start delivering the Volt or go public with specifics on each cell then it is all guess work.

By: Van

Van — Sun, 28 Oct 2007 12:45:17 +0000

Lets see, if the cost per KWH is $1600 and the Volt has 16, then the battery cost is $25,600. That is going to be a hard fit into a car that sells nicely under $30,000.

So either the bulk price will come down or the Volt we not be competitive with the Prius. I expect the actual price to be about $750 per KWH, or $12,000 for the battery. Toss it into a $14,000 car and voila, a $26,000 car that sells nicely under $30,000. Time will tell

By: ryfxor

ryfxor — Sun, 28 Oct 2007 08:31:12 +0000

Cycle life is a very tricky issue. first of all, only projections can be made, because of course nobody has never tested LifePO4 technology over a span of ten years!
It depends on temperature, rates used, depth of discharge…
if less than 5% loss is achieved after 1000cycles, it’s already a good figure.
juste think about your cell phone battery that is dead after a few years.
From the start, a battery is loosing capacity.When graphite anodes are used (the vast majority of Li-ion, including A123) the capacity decreases as soon as the battery is made, because of passivation reactions taking place on the anode and increasing slowly the impedance, even if the battery is not used.

By: AES

AES — Sun, 28 Oct 2007 04:49:57 +0000

re: Kent and the BYD vaporware:

If not LiFePO4, then the batteries BYD is referring to are likely Nickel-Iron.

http://en.wikipedia.org/wiki/Nickel-iron_battery

Only manufactured in China at the moment, and yes, quite cheap. But they’re also horribly inefficient to charge and discharge (65%, vs 99% for Li-ion), and have the absolute worst energy density. They’re also horribly low on power, and have horrible self-discharge (i.e. they “leak” energy).

Knowing that, I think it’s safe to say from a scientific perspective that BYD’s project is dead on arrival.

By: AES

AES — Sun, 28 Oct 2007 02:12:38 +0000

The current OEM price for the A123 cells is probably around 1600/kWh.

Killacycle pack is $12,000 for 7.5kWh.

Source
http://www.autobloggreen.com/2007/03/30/edmunds-editor-karl-brauer-offers-a-brief-opinion-on-batteries-f/