The Toyota Motor Corp. just showed off a brand-new prototype for a plug-in hybrid based on the Prius. The aptly-named Toyota Plug-in HV, the first plug-in hybrid car to be tested on public roads, can zip along at a top speed of 62 miles an hour and travel up to 8 miles on a single charge.

The car uses low-energy nickel-metal-hydride batteries, which are considered less suited to powering a car than lithium-ion batteries. Why, in that case, did Toyota build the Plug-in HV with nickel-metal-hydride batteries? Apparently, Toyota has built eight prototypes, with plans to study them under real-world driving conditions. So the Plug-in HV had to be approved for use on public Japanese roads--maybe the type of batteries mattered less at this point in testing. Right now, Toyota has no plans to put the car into production.

Battery performance is, not surprisingly, the major issue in battery-powered cars; Toyota, General Motors, and Ford are all working with battery companies to try to improve lithium-ion batteries. If things go well, we may see some plug-in cars for sale in the next few years.