My N810 keeps turning on and off by itself when charging. I'm quite sure the charger is fine. (I use it to charge other Nokia phones.) I recently flashed the device, so s/w-wise there should be no issue I guess. Would it be because of the failing battery, some soldering issues in the power connector, or something else? I hope I can at least use it as an alarm clock...

is it only when its charging ?
how does it behaves while charging with USB and with charger ?
is it different ?

and if you use it only with battery, does the battey last what it should last? try using an electric tester to check the voltage...

try charge it while powered off... it shouldnt power up if you plug it..

lets see your response and work from there..

I have the same symptoms with my 770. It was not use for a long time. My guess it is related to the battery.

When the charger is not plugged in, it doesn't happen. I don't understand the USB part. (Is it possible to charge it with USB connector?) I also guess it's related to the battery (showing 7days idle and 5 hours in use). Apparently, it doesn't last 5 hours in actual use... Or, maybe the loose connector? I don't have a multi-meter, so can't check the voltage...

BTW, does N810 work without battery (only with charger)? I'm not inclined to spend money for it... How to squeeze out the last drop of this old friend...?

It's almost certainly fixable by replacing the battery (though the fault is not necessarily the battery's, see bug 6206).

So, right now there is no fix other than getting a new battery and let this occur again when the battery ages? Oh........

At the point where it started happening with my battery it had less than half the original capacity left, which is a bit scary because some engineers consider them too "unstable" after degrafation to 80%

Try with different Nokia chargers before to buy a new battery because maybe you battery could be ok,
Even with the same external aspect the voltages/current differs in the Nokia chargers, furthermore nowadays electric devices and batteries have a broad range of input voltages.

It happened to me in the past and after many tests I found this solution (even I answer in other post), and I am pretty sure that is happening to you

If it's rebooting due to battery having worn out, a charger with lower current output is less likely to trigger it.

Thank you for help. The charger I'm using is 5V 890mA one. I have another in my office, which I don't know the spec right now. (I'm quite sure it gives less current.)

BTW, did anyone try to mod the device to charge from USB ports, maybe by opening up the device and soldering jumper lines from USB 5V to charger input?