Developing the 2011 Chevrolet Volt's Battery Pack

Testing battery packs is a 24/7 job at the battery lab, but enough of it is automated so that, for the most part, the employees work typical 9-5 hours. If they're performing a test that needs to be constantly monitored however, someone is there no matter the time. The automated system constantly monitors each and every test chamber and notifies employees if something goes wrong in a cell. If necessary, an employee can login remotely from anywhere in the world and abort the test.

The 16-kWh lithium-ion battery packs are set up in fully climate controlled test cells, wired to test up to two battery packs simultaneously. Engineers can set the chambers to a specific temperature and humidity, possibly relating to a certain region of the world where the Volt will be sold, or to torture test the packs (temperature ranges in the chambers vary from -68 F to 168 F).

When testing the battery packs, engineers simulate real world drive cycles. They'll start with a fully charged battery pack, deplete it, run the car in charge sustaining mode until the vehicle "runs out of gas," and then recharge the battery. Within this test cycle, the battery is made to respond as if someone were actually driving the car -- i.e. varying throttle input, braking, etc. Each test cycle takes around eight hours, and the cycles are run continuously. This means that in 24 hours, each battery pack being tested drives a simulated 1200-1600 miles. GM aims to complete the equivalent of around ten years of testing by the end of 2012 for battery warranty purposes.

In addition to the standstill battery testing chambers, GM has one chamber unlike any other in the world. One specially designed chamber allows for truly simulated driving. The floor of the chamber is attached to hydraulics that simulates vehicle dynamics. The chamber effectively allows on-road vehicular battery pack testing without the vehicle. This allows for much more in depth instrumented testing than if engineers simply attached data feeds to a battery pack in a Volt prototype.

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