Does an EV battery pack need a liquid cooling system? Automakers have different opinions. The Tesla Roadster and Model S have ‘em, the Nissan LEAF does not. Volkswagen initially designed its e-Golf with a liquid-cooled battery, but the production e-Golf, which is now on sale in Germany, and will arrive in selected US markets during the fourth quarter of 2014, relies on air cooling.
The company’s engineers have tested the e-Golf’s battery pack in places like Death Valley and Arizona, as well as cold-weather climates, and found no dramatic impacts on performance. VW’s Darryll Harrison recently told AutoblogGreen that the Panasonic lithium nickel manganese cobalt oxide cells used in the e-Golf had “the lowest self-warming tendency and the lowest memory effect of all cells tested. The need for a cooling system wasn’t there.”
Of course, this doesn’t mean that VW has given no thought to temperature issues. The company says it has developed a Battery Management Unit with an intelligent thermal control that allows the pack to remain within an optimal temperature window, and that waste heat is quickly directed into the chassis, away from the battery.
VW’s engineering goal for the e-Golf was to develop a highly efficient system, as opposed to one that focused on charge time or capacity. The e-Golf’s cells are designed for “gentle” charge and discharge, which helps to reduce heat, compared to cells designed for rapid charging. The lack of a cooling system also translates into weight savings.
On the other hand, the VW GTE plug-in hybrid (which debuted in February in Geneva, but won’t be sold in the US) does have a liquid-cooling system. According to Harrison, that’s because, whereas the e-Golf is designed to be efficient above all, the GTE is a plug-in version of the sporty GTI, and it will be tuned for performance.
(Headline updated 4/4/2014 19:00 EDT: “active cooling system” changed to “liquid cooling system.” Hat tip to Ule Amra)
Source: VW, AutoblogGreen