Let's start with what we know about the new Bolt's pack. It is supposed to drive the Bolt EV over 200 miles on a full charge. It weighs 960 pounds and is made up of 288 cells. Chevy's other all-electric car, the limited-availability Spark EV, had a 19-kWh pack and offered 82 miles of range. It had 192 cells and weighed 474 pounds. So, in the few years since the Spark EV was released, GM engineers have figured out how to get three times the energy capacity and almost two-and-a-half times more range out of a pack that weighs only about twice as much. And that doesn't even get to the price drops.
Speaking of those 288 cells, that number might sound familiar to regular readers because that's exactly how many are in the new Chevy Volt. But the packs in the Volt and the Bolt are entirely different beasts. For one thing, while the Volt cells are made by LG Chem in Holland, MI, LG Chem will make the Bolt's cells in South Korea. The cell chemistries are also different. We spoke with GM engineer Tim Grewe (again) and while he declined to answer some of our Bolt battery pack questions until more details are unveiled at the SAE World Congress in April, he was able to explain a few things.
GM has figured out how to get 3x the energy capacity and almost 2.5 times more range out of a pack that weighs only twice as much.
"The cell inside the Chevy Bolt EV was specifically designed for EV range so it's up on energy," he said. "That's a different cell chemistry than on the extended range Chevy Volt, which is a smaller pack, smaller energy but more power per cell. We work with all of those vehicle requirements and customer demands and we say how do we meet this and we change the chemistry to make it all work."
Comparing the 60 kWh in the Bolt and the 18.4-kWh pack in the Volt is really one of those apples to oranges issues, he said. "If you look at the Volt battery pack, how it went from where it was and where it's up to, from 38 miles to 50 miles, that was basic, overall industry improvement. Now, the 18 [kWh] to the 60 [kWh] is extended range vs. EV. It's all just about how do you change the mix inside the battery to get the energy up. This [Bolt battery] is definitely a generation past the Chevy Volt, because this is next year and this stuff moves fast, but it's not a huge 2-to-1 [improvement] or anything like that, it's mostly an EV vs extended range [situation]."