13-01-2013 1:15 - edited 13-01-2013 1:21
I've had my n8 for two years, my n8 will no longer charge through the USB port. I'm confident that what triggered this is not giving the n8 enough time to fully charge several times in a row prior to the battery going dead. Each time I "short" charged the phone for an hour or two and it showed full battery life after unplugging the charger, which I knew wasn't possible. I'm posting this in case any Engineers at Nokia are interested in this problem.
Also, as an Electrical Engineer myself, and having worked with Lithium Ion batteries, phone manufacturers would be better off relying on the voltage as an indicator of capacity rather than the artificially derived capacity ratings which "adapt" overtime.
Like you, I've had my N8 for over 2 years and am starting to find both charging points very temperamental. They have to be connected just right and not moved whilst charging.
From reading the forum's it would appear we aren't alone.
If "short charging" has messed up your charge calculation you may need to do a full re-set and installation of the firmware.
I'd start with the Battery out reset and work upwards, not sure at what level the data is held.
I discovered the charging issue after much fiddling. It's the micro-USB port on the phone side. USB female "hole" on the top side, has a thin piece of metal, split in the middle, that is slightly bent upwards, probably less than a millimeter and wasn't making good contact with the outside, top side of the micro-USB plug Wiggling the plug did nothing to help this problem. I got a safety pin and slightly bent the thin piece of metal down and voila, IT"S CHARGING!
I would check the USB cable first. Ground connection is made by two tiny springs on the USB (male) connector. The end of the cable connector can also be squeezed slightly to make a more secure connection to the pins in the phone.
And check for dust and muck inside the USB connector on the phone once in a while!