I've recently let the battery go down on my n810, it was sitting around for a month or two (I know, shame for neglecting the device). Of course, same issue -- white screen, reboot, white screen, etc.

My fix -- take out the 3.6 volt battery from my cell phone, hook wires to the battery terminals and jumper them to the n810 battery. Sort of like jump-starting it. Had to hold it in place for about 5 - 10 minutes till I had enough charge, put battery back in n810, which was just enough to get it to boot into the charging program. Now it is fully functional again. Whew.

Disclaimer: I am not recommending this to anyone, as charging a lithium battery from an unregulated source can be hazardous and may cause an explosion. In my case I was constantly monitoring both batteries temperature, but I could see the potential for a problem.

Oh, and for extra geek points, I didn't have any wire with me at the camper. Did have aluminum foil though, which made for some nice and dangerous uninsulated conductors. Sometimes I'm surprised I still have all 10 fingers.