Please be aware that gas-electric hybrid and plug-in hybrid are completely different vehicles.

Prius/Camry Hybrid are designed as a gas-electric hybrid.
The Prius battery history is...
NHW-10 40 modules
NHW-11 38 modules
NHW-20 28 modules
Toyota reduces the battery capacity, but the results are higher performance, better fuel economy and wider trunk space. It is the innovation.

Also, please be aware that using a lot of battery power means you'll see worse mileage.
Have you ever seen the pulse and glide article?
http://hybridcars.about.com/od/owner...seandglide.htm
To see a good mileage number, avoid using battery power.

Prius/Camry Hybrid are not good candidate for plug-in hybrid.
My opinion the plug-in kit for Prius is a joke.
The better platform for the plug-in hybrid is a series hybrid like Chevrolet Volt.

Ken@Japan