Everyone tends to agree that 100% battery powered cars need batteries with energy densities only achieved with lithium ion technology, but virtually all hybrid cars still get by with nickel metal hydride batteries. No more.
Today in Geneva, Switzerland, at the 78th International Motor Show, General Motors announced that by 2010 they will be using lithium ion batteries for their entire (and expanding) hybrid vehicle fleet. Just for clarification: There are three basic ways to use electrical systems to power a car (1) a 100% battery powered car such as the vaunted Tesla Roadster, (2) a “series-hybrid” car, where the gasoline (or diesel) engine has no connection to the drive-train, only to an onboard generator that powers an electric motor for traction – such as the upcoming Chevy Volt, (3) and a standard hybrid, or “parallel hybrid,” where the gasoline engine and the electric motor-generator(s) share responsibility for providing traction to the wheels. Based on today’s announcement, GM may be the first automaker to deliver lithium ion batteries in standard parallel hybrid vehicles.
The advantages of lithium ion batteries go beyond the obvious fact that they contain equivalent energy storage with 40% less weight when compared to nickel metal hydride batteries. They also deliver about 33% more surge power compared to nickel metal hydride batteries. Providing power to electric motors from batteries has been problematic not only because of the low energy storage capacity of batteries relative to their weight, but also because they can’t easily discharge large amounts of electricity when required to provide surges of energy. The lithium ion battery is significantly better than the nickel metal hydride battery in both of these critical areas.
GM’s next generation hybrids will utilize not only more voltage from lithium ion batteries, but will also employ a larger motor generator than GM’s current hybrids. This combination will allow the electric motor to provide more torque throughout the RPM cycle, which in-turn will reduce the constraints on downsizing the turbocharged gasoline engine. Because small turbos have trouble in low RPMs as well as kicking in smoothly at high RPMs, the electric motor assist plays a vital role in providing a smooth torque profile throughout the RPM range. GM’s use of a higher voltage lithium ion battery combined with a more powerful motor-generator system completely solves this problem.
It is still possible to hear criticism from time to time regarding GM’s decision to recall the EV-1. But the ecosystem of manufacturers for key components, batteries in particular, was not in place back then. Meanwhile, GM learned an awful lot about what happens when you have a large battery mass in a car. The bottom line – when a large battery is drained, it is an amazingly huge bunch of dead weight. Hence GM has decided to design electric cars with batteries weighing 400 pounds or less. Unless this changes, GM will never deliver a 100% battery powered car. But GM is very close to converting their entire fleet of parallel hybrids to use lithium ion batteries, and they are very close to delivering the world’s first series hybrid cars, the Chevy Volt and the Flextreme.
Toyota won the first round in the hybrid car revolution by achieving volume production of the revolutionary Prius. But GM could be favored to win round two, with their parallel hybrids and series hybrids – using lithium ion batteries – that are affordable and available in mid-size and larger. GM claims they will be delivering these cars in quantities of 100,000+ within a few years.