I have had my Nokia N810 for probably 2 years now with the original battery but I didn't use it for a while and the battery still seems to last as long as if it was brand-new.

I have put the OS onto my 8GB micro-SD card using that bootloader I forget the name of just know it looks like Microsoft's XP Bootloader.

Anyway, when i use my USB charger or my other Nokia charger everything works like a charm, I have no problems.

Yet the minute I put in the AC-3U or default charger that came with the device I can have totally random reboots of the device and the other day I awoke to the boot menu with TEST written in large green letters.

Why would only the original charger be rebooting the device?

Do the other chargers supply less current? The n810's charger is 890mA and non-n810 Nokia chargers I have are 400-600mA. The higher charge rate can cause reboots if the battery has problems.

Charge it with the others and maybe the battery will allow the default charger after a couple weeks. Otherwise you'll probably need a new battery, they don't last forever, even if rarely used.

I have the same problem. It happens only if battery is below 50%. I have found a thread here, that explains how to find exact reason for this. Mine is the battery. I confirmed it with exchange my battery with the one of my phones. Reboots stopped. Anyway you should find the real reson and proper solution fo your case. Just search TMO.

Looks like it definitely has to be the battery.

It will not even hold a charge for 12 hours when before I used to have it sit on sleep for like 3 days still working.

Now comes the fun part of finding a battery that isn't extremely overpriced but not so cheap it's likely to totally leak/explode in my Nokia.

http://talk.maemo.org/showpost.php?p...&postcount=402

I ended up purchasing a PowerGen (PG) BP-4L from Amazon back in July (5 months ago) and have been quite happy with it. YMMV