I have the new model (bought in January 2008). I did remove the
"battery" cap. I found an assembly of 3 metal ion sub batteries.

These batteries are made by GBS in UK. I contacted them in order to
have spare batteries.

I hope that opening the battery cap will not make my flights invalid.

I am a little disappointed about the weakness of this battery assembly
(only after 6 months, I got already problems !).

Bruno