Last year at the LA Auto Show, the Volkswagen e-Golf was introduced with a water-cooled battery. Later at the Detroit Auto Show, Volkswagen had quietly removed all terminology related to water-cooled batteries, and then most recently, at a Volkswagen drive event in Germany, a keen reporter from Green Car Reports noticed the battery on display had no liquid-cooling components.
Now, it’s official. According to Volkswagen’s Darryll Harrison, the brand’s US manager of brand public relations west, said that battery performance was not impacted at all by temperatures when using the right battery chemistry. As a result, Volkswagen deemed it unnecessary to have liquid cooled batteries that add complexity, and extra weight that decreases range (albeit a small amount I’m sure).
Volkswagen is using a battery chemistry that is lithium nickel manganese cobalt oxide, and after testing in Death Valley and Arizona, shows the ‘lowest self-warming tendency and lowest memory affect’ of all the batteries tested, during both operation and quick charging at high ambient temperatures. Simply put, as Harrison said, “the need for a cooling system wasn’t there.”
Volkswagen’s new e-Golf does use a thermal control to regulate the amount of energy coming out of each individual cell to keep heat down, and any heat energy that is generated is dissipated into the electric vehicle’s chassis away from the battery pack.
Here is the full statement from Harrison, as he emailed it to AutoblogGreen
Generally speaking, regarding the system, it’s important to note that the e-Golf was designed with efficiency in mind. The battery pack utilizes ultra-efficient lithium-ion cells that deliver 25Ah per cell with an energy density of 59Wh per lb. The pack is comprised of 264 cells, packaged into 27 modules (of either 6 or 12 cells) delivering 323 volts and weighing in at 700 lbs. As it relates to battery temperature, VW has developed a Battery Management Unit with an intelligent thermal control that allows the pack to remain within an optimal temperature window, helping to maintain performance and range in a variety of temperatures. This system allows the e-Golf to operate, even in more extreme temperatures, without the need of a cooling system and without dramatic impacts in performance based on testing.
In terms of the battery pack, the engineering goal was to develop a highly efficient system as opposed to one that focused on charge-time or capacity (like some of our competitors). In partnership with Panasonic, VW utilizes a lithium-ion cells designed for gentle charge and de-charge during use which helps to reduce heat and energy consumption often associated with cells designed for rapid charging and de-charging. Our engineers refer to them as “marathon cells.” Additionally, without a cooling system weight savings are achieved which aides in overall efficiency of the vehicle. Due to the efficiencies achieved, minimal waste heat is created during operation (i.e. during fast charging) and is quickly directed by the battery metal structure into the chassis, away from the battery, helping to prevent extreme temperature conditions inside the pack.
Our engineers tell us that the e-Golf has passed various long-term engineering evaluation milestones in desert temperatures and cold weather climates, without the necessity of a cooling system.