Step 11: Battery.. POWER!
Due to size constraints, i was limited to a small battery.
My choise was a 2000mha LION 7.4v cell. LION batteries don't like to be drained, so be prepared for a low life expentency.
The 2000mhz battery gives my wall-e about 60 minutes of life between charges.
You can purcahse your battery at any Battery Depot or similar outlet.