Originally Posted by jurepu
If anyone is interested in connecting the external battery with modification I have made I give you some simple solution.
You can easily use internal battery with jumper ON white/black wire. The external battery can be connected using servo cable connecting red/black wire. I use 3.7V Li-ion cell phone battery and it works well.
Just a word of warning... think what happens if you plug the external battery the other way around: batteries would be in series which means double voltage to the electronics. Not good at all.
A four pin connector with one pin not connected would be a safer solution.