Unlike the engine and electric motors that make up the rest of the Hybrid Synergy Drive system in the 2010 Toyota Prius, the battery pack is the one component that's changed very little.

It has the same 168 1.2-Volt nickel-metal-hydride cells, providing a total of 1.6 kilowatt-hours of energy capacity. Peak power output is 27 kilowatts (roughly 36 horsepower).

As you might expect after eight years, they're contained in a more compact design with updated electronics that allow slightly higher power output. Among other benefits, cargo volume in the rear load space is slightly increased.

But early rumors for a new, higher-capacity lithium-ion battery pack for the 2010 Prius turned out not to be true. Toyota is fitting a larger lithium-ion pack to the 100 or so Prius Plug-In conversions it will offer to fleets late this year, but so far, it has said nothing about a lithium pack for the standard Prius.

Which leads us to wonder: If the 2010 Prius is the third generation, might there be a "third and a half" generation coming in a few years? Same great car, even better battery?

We can dream, anyway ....

2004-1009 Toyota Prius battery pack, second generation

2004-1009 Toyota Prius battery pack, second generation