[ad#post_ad]After all this time its pretty amazing to hear GM's final decision on the Chevrolet Volt's battery warranty.  Eight years or 100,000 miles.

We have known for a long time that GM was aiming towards ten years/100,000 miles as a goalpost, though using that figure specifically as a warranty was never confirmed.

This warranty is being described as the longest-lasting GM offers on any of its products, illustrating the very high level of confidence the company has in its extensively engineered and managed lithium-ion battery pack.  It exceeds by three years the warranty GM offers on its powertrains.

The warranty coverage includes all 161 components of the Volt's battery, its charging system, thermal-management system and components of its electric drive, and it is transferable to other vehicle owners. GM confirmed that the 400 pound pack houses 288 cells in nine modules.

Volt vehicle line executive Doug Parks GM provided some additional details about the warranty.

First the warranty is good at delivery, no minimum number of miles are required, and the mileage is calculated in terms of vehicle miles, not generator miles.

It was long thought GM must achieve a ten year warranty specifically for California and the other CARB states. This turns out not to be the case.

The "warranty announcement covers all states, including California," said Parks.  "California does not mandate 10 years/150,000 miles for all vehicles."

The reason, as it turns out, is that GM did not submit the Volt as an advanced technology partial zero emission vehicle to CARB (California Air Resources Board). Therefore, GM is not required to meet those warranty criteria. It also means California Volt buyers will not get the $5000 tax credit. GM expects to achieve AT-PZEV designation in the 2013 model.

"The Volt's battery warranty announced this week is based on the remarkable results of our engineering and development testing," GM spokesperson Shad Balch told GM-Volt. "When we complete the additional engineering and submit the vehicle to CARB for AT-PZEV certification it will include the required 10/150K battery warranty."

"We expect to do this with the 2013 MY, which will be available mid-2012," he added. "AT PZEV for 2011 MY would have required additional costs and delayed the launch. We could have pushed back the launch - but customers want a practical EV now."

"California's rebate program has funds to cover fewer than 700 customers, total, for vehicles from all manufacturers - and future funding is uncertain," he added. "Rather than sticking it to thousands of our customers with a delay, we chose to remain on track and launch the Volt this year."

GM is continuing to look at battery performance beyond the ten years as well. "The batteries are being validated beyond the warranty period," said Parks. "We continue to test to see how far they will live."

Parks also noted that the battery is warrantied for both level 1 (120-v) and level 2 (240-v) charging, and that the use of either has no effect on performance or longevity. He said that if a pack wound up needing repair some work could be done at local dealerships. "However all refurbishment/cell replacement will be done at a central specialized repair center," he added.

Parks noted the warranty will cover "all customer charge cycles," even if owners charge the car multiple times per day.

Overall GM noted that its battery warranty was significantly longer that what Tesla offers on its Roadster which is "3-year, 36,000-mile standard," according to Tesla spokesperson Rachel Konrad. "You can buy a two-year extension," she added. Tesla also offers owners the option of paying a non-refundable $12,000 to get a free battery replacement at seven years..

And for what seems like the first time, GM beat Nissan to announcing something about its electric car.

According to Nissan North American Director of EVs, Mark Perry, Nissan has "no comments yet," on the air-cooled LEAF battery warranty. "We will release a bit closer to launch," he added. Nissan has surveyed its $99 reserve holders about their battery warranty expectations, and may be aiming for 5 years/60,000 miles. The LEAF, as a zero-emission vehicle (ZEV) will be eligible for the $5000 California credit for those who can get it.

"No battery warranty requirement/regulations from CARB for ZEV," says Perry. "Nothing for the air resources board to regulate."