Can you charge non-Plug-in hybrid

[Johnny8]

Hello, I know you can't charge standard hybrid, I know they are 'self charging', I know I loose my warranty and risk my life, blablabla... However, putting some electricity to your hybrid battery must improve its fuel efficiency.

The new Honda Jazz/Fit/Life hybrid works like an electric car with a petrol generator until some 80 km/h. It have 0.86 kWh battery. That would be enough for about 4 km, considering electric cars consumption. Of course, the battery is not able to be drained in such a short time. Still, charging it should help, plug-in batch or not, right?

Now how to do it? The battery is "high voltage", so I have to know that number and find adapter. Find some connector to the battery,... I have no idea, what could happen, what about the electronics?

I wish they fill up that under-floor boot space with a battery and include self-winching power cord such as vacuum cleaners have. Mild Plug-in hybrid with 10 km of range...