Battery lvl drop from 40% to 9% after reboot

[makaveli]

Hi o/
I just registered on the forum because i have a weird problem.
My GSII first shows 'no network service' and it won't change unless i do a reboot.
after the reboot my battery went from 40% to 9%
It happened 3-4 times in the last 5 days.
I already did the latest ics update via kies.
the phone is not rooted.
I did the hard restart.
nothing helped.
Need serious help xD
Here is the picture from the last drop http://prntscr.com/acp0e

[greenman]

The power fell of the cliff!!!
After changing to ICS from gingerbread it is recommended to carry out a factory reset and clear cache in Recovery.
Think this may resolve your problem.

[makaveli]

Yup a big jump
I did the factory reset but didn't clear cache in Recovery.
How to do that?
A trick with the buttons?

In the meantime the battery lvl jumped from 9% to 12% :/

[greenman]

Recovery is Press and hold Volume up + Home button + Power button until in blue recovery screen.
Use volume button to highlight and power button to select.

[RichH]

I think this is more of a calibration issue. The power meter is showing a rise in battery level which clearly isn't possible unless it is being charged so I think the power is there but is mis reported. Try running the battery flat and charging in one go with wall charger with phone off. Then when full remove charger and battery for 5 mins before restarting phone.

[makaveli]

Thanks for the suggestions.
I did the factory reset and cleared the cache.
I'll try RichH's charging solution and I'll report if this happens again.
Thanks and sorry for bad English o/

[greenman]

Your network APN settings (Access Pont Names) may have you be re installed.
Contact your provider or visit their website.