By Jim Taylor, Editor MACS ACtion Magazine
We ran some entries recently on how the Chevrolet Volt accomplishes its sophisticated thermal management tasks. Chevrolet keeps releasing information (and some PR…) and we keep finding it. Here’s an update, issued by GM a few days ago.
The Volt’s ability to operate gasoline-free on a day-to-day basis and carry an eight-year/100,000-mile battery warranty is due to active thermal management of the advanced lithium ion battery pack.
“Every battery has a temperature sweet spot where it provides the optimal blend of power output, energy capacity and long life and we keep the Volt right on that target,” said Bill Wallace, General Motors director of Global Battery Systems. Batteries that are too cold are reluctant to release electrons while batteries that run too hot can see a significantly shorter life.
The Volt’s T-shaped battery pack consists of 288 individual cells arranged into nine modules. Plastic frames hold pairs of lithium-ion cells that sandwich an aluminum cooling fin. The design and construction of that aluminum plate is critical to ensuring an even temperature distribution with no hot or cool spots across the flat, rectangular cell. The battery pack has its own cooling circuit that is similar to, but independent from, the engine cooling system.
The Dana Corp-manufactured cooling fin consists of two lightweight aluminum plates joined by a proprietary clean nickel-brazing process. The carefully designed grooves stamped into the plates form channels that allow battery coolant that is pumped through the pack to flow over the entire cell surface.
“Three different systems are used to regulate the temperature of the coolant,” said Wallace. “When the Volt is plugged in and charging in cold weather, an electric heater at the front of the battery pack is used to warm the coolant and pre-heat the battery. During normal operations, the coolant is passed through a heat exchanger at the front of the car, while a chiller in the air conditioning circuit can be used to dissipate heat from the battery when temperatures really climb.”
The management system monitors feedback from 16 thermal sensors arranged throughout the battery pack to maintain a spread of no more than 2 deg. C from the optimal temperature across the pack.”
When having your mobile A/C system professionally serviced, insist on proper repair procedures and quality replacement parts. Insist on recovery and recycling so that refrigerant can be reused and not released into the atmosphere.
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