VW e-Golf, like LEAF, will have air-cooled battery
Every battery is different. Automakers use different li-ion chemistries, different shapes and sizes of cells, and different thermal management systems. Nissan made headlines for huge range loss experienced by some LEAF owners in the southwest United States because the air-cooled battery could not sufficiently moderate its temperature.
Since then, rather than switch to a liquid cooling system, Nissan has tweaked their battery chemistry to be more heat-tolerant. Adding a dedicated liquid cooling circuit, as in vehicles like the Tesla Model S and Chevrolet Volt, adds cost, weight, and complexity which Nissan is loath to do as they attempt to drive costs down.
Volkswagen has said that the e-Golf, the electric version of the popular hatchback, will not need a liquid cooling system. Arriving on American shores toward the end of this year, the e-Golf employs a lithium nickel manganese cobalt oxide battery chemistry from Panasonic that boasts “the lowest self-warming tendency and the lowest memory effects of all cells tested. The need for a cooling system wasn’t there.” (VW’s Daryll Richardson, via AutoblogGreen).
The e-Golf will still have a thermal management system of sorts, integrated with the Battery Management System. The controller monitors each cell individually and regulates how much energy each cell produces to moderate temperature rise. Allegedly, waste heat will be redirected into the vehicle’s chassis so as to avoid unacceptable temperature increase in the battery.
One rather unfortunate trade-off that comes with air-cooled systems is that vehicle performance must be restrained slightly because demanding high current from the battery raises the temperature quickly. That is one reason why the VW GTE, the plug-in hybrid version of the high-performance GTI, will use liquid cooling for its battery. The e-Golf is more optimized for efficiency than performance, so liquid cooling isn’t absolutely necessary.
VW engineers say they have rigorously tested the battery in extremely hot climates and found that an air-cooled system would be sufficient for their needs. We’ll take a wait-and-see approach and keep tabs on real world performance once the e-Golf arrives, but I wouldn’t bet against the German automaker. With Nissan’s mistakes to learn from, Volkswagen has complete confidence their solution will withstand the rigors of even the warmest regions.