A while ago I tried to connect 4AA batteries to my N800 and used a diode to prevent the power from the internal battery to go to the external ones. This seemed to in some extent charge the internal battery but it got impossible to get any sense out of the battery indicator on the N800 and it seemed that it did empty the int. battery when the v of the ext. batteries had dropped a bit.

Are there some people here with a bit more knowledge of electronics than me that could tell me how to get use of all the 2500 mAh that I have in my AA batteries, some kind of charger chip that I could solder together. If I could get this to work and got some 3000 mAh batteries to add to the internal 1500 mAh I guess I could run the tablet three times as long.

Mabye the voltage needs to be pumped from 4.8v to 5v and expecially when the batteries starts to run low and the voltage drops. Mabye the N800 charger uses some kind of pulse to charge the tablet like some battery chargers do...

Is there someone else that has attempted something similar?

Maybe this would work:
http://www.instructables.com/id/Mint...d-USB-charger/

Someone that want to share some thoughts?