I recently put w800 firmware in my k750. After that, i noticed a strange behaviour of the phone(battery): even it was almost fully charged, when i started it, the battery level was indicating only 15%. But after playing a little it increased (first to 50% and the to 80%). At the service they told me it isn't a hardware problem, so I put back k750 firmware and for a while this issue stopped. Last night i pulled out the SIM card and the battery for an hour and the problem reappeared. Any ideas ?