At the 2007 Detroit Auto Show, General Motors unveiled an eye-catching — in more than one way — concept. The Volt’s futuristic looks caught the public’s attention but it was the technology underneath the concept’s skin that was truly noteworthy. It featured a lithium-ion battery pack that enabled the concept to travel 40 miles on a single charge and had a 1.0-liter turbocharged gasoline engine to act as an electricity generator after the battery pack was depleted.
Fast forward three years and a few things have changed from the concept but the Volt is a reality — or shortly will be for customers in select regions around the world. The Volt launches in select U.S. markets this November and its siblings, the Vauxhall and Opel Ampera, will be sold across the pond in Europe. GM also announced it will send the Volt to the Far East as a Buick next year.
When the Volt concept appeared, lithium-ion battery technology hadn’t yet been used in automotive applications, but was much more promising for the future of electric vehicle transportation than previous nickel-metal-hydride and lead-acid batteries. Here’s a look at GM’s battery research lab that, in three short years, made the technology behind the Volt — and its series-hybrid Voltec architecture — possible.
General Motors is proud of its battery lab, and it very well should be. Located in what used to be a conventional internal combustion engine powertrain research facility built in 1950 at GM’s Warren Tech Center, the exterior of the building doesn’t portray the advanced technology located inside. It’s one of the most advanced battery research facilities in the world with over 33,000 square feet dedicated solely to battery research. This past April, GM announced it was adding on to the existing facility, almost doubling it in size. When the addition is complete, the battery lab will measure over 63,000 square feet.
Currently, the lab is split into two separate sections, one used for testing battery packs and the other primarily for testing individual cells. For those unfamiliar with battery technology, each battery pack in a Chevrolet Volt consists of a set number of cells wired in series and parallel to achieve the desired output (in voltage and amperage). The key figure to come from the battery pack wiring is the battery capacity, a total of 16 kWh in the Volt.
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.
Across from the battery pack test facility is GM’s battery cell test facility. The facility allows GM to test single cells to see how they react individually to different conditions. Another reason for the cell testing facility is to test cells from different manufacturers before deciding on one brand for a battery pack. The cell test chambers operate exactly like the pack test chambers, but are smaller and have a wider range of temperatures.
What is perhaps [going to be] the coolest part of the battery test lab is attached to the cell testing facility — the 30,000 foot addition to GM’s existing battery lab. There, engineers will conduct battery abuse testing to further battery research. Once completed, it will be one of the only independent battery abuse testing centers in the world. GM eventually hopes to open up an independent battery research segment within the company that would research and test batteries for outside companies without fear of technology infringement.
After more than three years of work, we’ll see the biggest advancement in battery technology to come out of GM’s lab this fall with the Chevrolet Volt. Engineers at the lab test more than Volt batteries and packs, but the Volt has been the big project for the last several years. Other projects include the next-generation 2-Mode Hybrid and upcoming mild hybrids.