The thing that strikes you when you enter GM's Battery Systems Lab (BSL) is the EV1. On the hallway walls are the promo images of the Chevy Volt. For our visit, GM also set up two of the T-shaped batteries that powered these vehicles. The older one that moved the EV1 weighed around 1,200 kg lbs. whereas the Volt's powerpack will weigh "just" 400 kg lbs. Standing side-by-side, the batteries are impressive. It's as true to GM today as it was in the '90s that the T-shape is the best way to have a lot of room for the cells without eating into the trunk space.

Micky Bly, director of Global Hybrid Vehicle Integration and Controls, spoke to us for a little bit (sorry for the background noise in the recording, but he was speaking in the BSL while testing was going on) about the tests that GM is running on the batteries - from A123 Systems and Compact Power Inc. - in the lab and on the road.

In the BSL, GM can simulate any possible condition that the batteries might encounter when they're plugged into the grid - high loads, brownouts, etc. While these tests provide good information, the real challenge comes on the road. This month, the li-ion batteries will move out of the lab and into a 2005 Chevy Malibu mule vehicles for runs out at the Milford Proving Grounds. The Malibu has been running on the proving grounds since about October with a lot of the E-Flex control software, including the regen-braking, the small ICE and so on. One thing that the battery tests have discovered already is that at least 20 percent of the 40-mile electric-only range that the Volt will have will come from capturing the braking energy.

Listen to Micky Bly:

A big challenge for the Volt team is figuring out how to pack two years of testing so full they will yield ten years of data. This is being done, in part, by Lance Turner, engineering specialist-battery integration and test, and his team in the BSL. Turner explained that the packs are being tested 24/7 in a way that simulates how they will be used in real life. Some packs are being tested in large thermal chambers that simulate different ambient temperatures and seasons. The heat also accelerates battery aging. Turner would not tell us how many cells are in the packs, just that we'd find out soon enough. If you're hoping for insight into which supplier GM is leaning towards, all Turner would say is that both packs are performing quite similarly right now. As I wrote in my initial post, the Volt will only use half (that is, 8 kWH) of the 16 kWh of power in the pack. The operating range will probably be between 80 and 30 percent or 90 and 40 percent, with the latter being preferred. Roland Matthe, GM's engineering group manager, E-Flex rechargeable energy storage system, was also on hand. Listen to Turner and Matthe:

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