Found two interesting ICs:

First is a freescale one where google search with the part number shows up with some pages in chinese and then pages on freescale forum with people complaining that they can't find info on the part (and other people hinting that it's some "secret" OEM chip which would explain why there is no public info).

TEC103 (charge logic), as this device could also charge the AA battery inside (if it was of supported chemistry), the "problem" is that it won't work even the other way with "wrong" voltages (so 4AA was no-go, had to try though). 2AA worked fine and the datasheet also says it's ok (I guess the device itself was made 1AA for size reasons)

With two AA alkalines it was drawing about 700-800mA from the batteries (the connection terminal is small and I didn't want to solder anything to it at that point so the connection was less than perfect thus not exactly accurate figures here, saw over 1.2A for a moment as well but that might have been a misplaced probe).

Now test charging N810 with two NiMH batteries, seems to work fine. Picture: http://www.qaiku.com/home/rambo/show...e6b542f9b2f9b/

Ordered the thing agent770 suggested (thanks for the suggestion). They claim 1A charge current then it's twice the USB spec, and the official Nokia charger I have around is 890mA so 10% increase there as well.