Korg Poly800/EX800 Users

Hi, 

I got a hold of a poly-800 recently, and it doesn't hold patches so I figured the battery had run out. When I opened it up I found that the place where the various tutorials say the battery should be is just empty, with 2 empty square pads sitting there.  

Not sure why this is... I mean, who would desolder the battery out and not replace it?

Anyway, I'd like to solder a new battery in (I'm not so worried about getting a battery holder), but I'm not sure which pad is + or - , and how is the best way to solder it on (or do I *need* a holder?) 

any info would be appreciated, cheers guys

Jason