The Incredible Shrinking Electric Car Battery, Boosted by Data

After the first generation of electric vehicles, today’s heavy, expensive battery packs could start to make like Alice after a sip of the White Queen’s shrinking potion. It’s not just technology advancements that could pave the way to smaller, lighter battery packs in electric vehicles — but also the collection of data as automakers learn more about how these cars perform on the road.

For gen-1 models, many automakers are “overcompensating on battery pack size relative to warranty,” said Saul Zambrano, Director of utility PG&E’s (s PCG) Integrated Demand-side Management Core Products team, at the recent Berkeley Stanford Cleantech Conference in San Francisco.

Automakers, Zambrano explained to us this week, generally restrict batteries from discharging below about 50 percent. These limits on “deep discharging” are meant to “maintain battery life,” he said. But once data comes in from real-world use in different climates (in conjunction with improvements in energy density and battery management systems), Zambrano anticipates that electric car makers will be able to “reassess the deep discharge level relative to actual usage,” and potentially lower it. That could translate to smaller battery packs in later generations of electric vehicles, basically on the principle of getting more bang for the buck.

The 34 kWh battery pack in Coda Automotive’s upcoming electric sedan, for example, will weigh about 700 pounds and deliver 100-120 miles of range, according to Coda Chief Financial Officer Dan Mosher. For the upcoming Chevy Volt, which will have a gas engine kick in after 40 miles of electric range, 200 kilograms (a little over 440 pounds), “is the rough estimate within the realm of a few digits for battery weight.” That’s according to comments from Micky Bly, the executive director of global electrical systems, hybrids, electric vehicles and batteries for General Motors (s GM), in a recent media briefing.

After that first generation, “based on durability and warranty data,” Zambrano said automakers will likely learn more about how far they can push the limits on those batteries. So if you can get 100 miles of range out of a 700-pound battery pack today when the discharge limits are typically set around 50 percent, you could in theory get more miles out of that same pack if it’s set to allow deeper discharging. Data from upcoming plug-in vehicle deployments could help automakers understand whether and how much they can afford to shift that setting — without foreshortening battery life and risking the cost of replacing batteries under warranty.

On the other hand, you could get the same number of miles out of a smaller pack, helping to reduce vehicle weight. So as the data rolls in and gets incorporated into vehicle designs, said Zambrano, “range will begin to extend.”

Photo courtesy of General Motors

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For a discussion about best practices for large data management, check out the panel on “Dealing With the Data Tsunami” at Structure 2010 next month in San Francisco.