You don't have to have the battery in the slot to power the computer; all you need is the power supply. I take mine out from time to time in order to let it drain.
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Cheers! :-)
- JediJoker

Current:
- "ProBook:" 15.4" MacBook Pro Core 2 Duo 2.33 GHz
- Mac Classic II
- Old PowerBook

Moved On:
- "The Book of Power:" 12.1" PowerBook G4 Aluminum 1.33 GHz
- Purple iMac