My battery capacity is decreasing very fast,... moreover now I can charge with a charger 5.2v and0.5mA (it isn't from nokia) but I can't with a nokia (AC-3X) 5V and 350mA

Months ago I bought a new battery in ebay, but the real capacity was less than half of my original nokia battery instead of the capacity printed in the battery ...

I am afraid to buy a new one in internet because there are cheap and more expensive but how could i be sure the it is a good battery? have you bought any?

And buy a original nokia in phone shop is too expensive...

I have found that using different chargers you can avoid the problem, but for it is interesting to see that sometimes you need one and other time other to wake up the charging process.

I have 3 nokia chargers and 2 from other phones (with the connector replaced). I would like to measure the real output voltage supplied to N8x0 in the charge process to have more detail and to reach a conclusion...

furthermore I found the same problem in N800 and N810

As batteries get old, a lower power charger gets better results because the charging current is lower.
I bought a mugen battery in august for the n810, for about 20€ shipping included. While I think it is not as good as the nokia one, it works well.