April 13, 2009
Chevy Volt Battery Overengineered Due To Unknowns

The Technology Review has an interesting article about Chevy Volt. A second generation of the forthcoming pluggable hybrid Chevrolet Volt will probably be cheaper once factors influencing battery life are better understood.

One way to save money is by improving the battery system. For the first version of the Volt, GM has taken extra pains to make sure that the battery will last, Posawatz said. A dedicated heating and cooling system will prevent the temperature extremes that can quickly degrade a battery. In addition, because discharging the battery completely can also shorten its life, control systems keep the battery from being discharged more than about 50 percent. But these measures could be overkill, Posawatz noted. "We have put in place a lot of extra fail-safe engineering solutions," he said. "So there are some opportunities [to reduce costs] as we refine the design."

Regards those control systems that prevent more than 50% discharge: If the battery warranty is less than the 10 year expected life of the battery then once the battery goes off warranty it would be nice of owners had a way to change the control system calibration to allow deeper discharge. If the owner is willing to take the financial risk then why not let the owner do deeper discharges in order to get longer ranges? A 75% discharge would increase battery range from 50% to 75%.

If battery prices fall then the 50% discharge limit will make less economic sense as replacements become cheaper. Similarly, when the price of oil once more goes above $100 per barrel and even higher the trade-off between avoiding battery replacement costs versus avoiding money on gasoline will shift toward the latter.

Share |      Randall Parker, 2009 April 13 10:11 PM  Energy Batteries


Comments
Engineer-Poet said at April 14, 2009 11:21 PM:

It makes no sense to demand a 10-year service life from the battery.  The car simply cannot run without tires, but who's asking for a 10-year tire?

The PHEV battery should be considered a service item, with a maximum cost over the warranty period (given non-abusive use patterns).  Anything over that cost should be covered by the warranty.  That lets many different battery technologies compete on the basis of cost/mile, rather than the utterly artificial criterion of 10-year lifespan.

Michael said at November 2, 2010 1:14 PM:

"It makes no sense to demand a 10-year service life from the battery."

Yes, it does, because the cost of the batteries is a significant portion of the cost of the car.

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