Toyota, Daimler and BMW have all turned to the laptop battery cell technology utilized by Tesla in the Roadster to power at least one of their electric car models. For Toyota, the laptop-style cells will find a home in the automaker's limited test fleet of battery-powered RAV4s. Daimler has chosen to power its Smart ForTwo Electric Drive and Mercedes-Benz A-Class E-Cell with the small, cylinder-shaped cells while BMW outfitted its Mini E prototype with the Tesla Roadster-like power supply. Judging by these inclusions, it could be argued that the small-format cell pack is the way to go with electric vehicles.
But wait. BMW's upcoming Megacity and ActiveE electrics will forego the laptop-style cells in favor of large-format ones provided by SB LiMotive. Additionally, Toyota has not committed to a single battery type for its mass-produced electric vehicles and will try out large-format units on the upcoming plug-in Prius and iQ-based battery electric and even Daimler has enlisted the help of Evonik to develop large format cells for use in the company's future EVs.
Choosing between laptop cells and the larger format, car-only batteries, according to Automotive News (sub. req.), is a decision that's based on cost and availability. Large format lithium-ion batteries cost around $700-$800 per kilowatt hour to manufacture. Whereas mass-produced packs that utilize laptop-type cells could set automakers back as little as $200 per kWh and are an off-the-shelf item that allows companies to build EVs while adhering to a strict time schedule. What all of the small-format programs listed above had in common is that they were quick-out-of-the-gate programs that OEMs used as promotional and test programs and, since they needed something fast, they were able to make use of Tesla's available and tested technology. Other automakers, like Nissan, Chevrolet and Mitsubishi, have chosen to only use large-format cells for their mass-market plug-in vehicles. There's no obvious right answer today about which size format is right for every EV and, with automakers flip-flopping between battery types, could we see another Beta-versus-VHS-style battle in the near future? If it results in better EVs, maybe that'd be a good thing.