Default Batteryindicator messed up

Hey people, i've got a kind of anoying problem.
Sience a while back my batteryindicator shows the wrong battery precentage. When i've fully load the battery and unplug the charger, I can use the tablet for several hours without the batterybar is changing below 100%. But after a time the batterybar is starting to changing normaly - until you reach about 50%. Then the tablet completly dies, and cant be started again without loading it.

It seems like it's not completly calibrated. I've treid two things to fix the problem,
First of all i've tried diffrent Roms and kernels.
Second I've tried the Battery Calibrator app from Play Store without success.

Do someone know what the problem could be, or even better - do you have any solutions?

I am currently on latest OmniRom, a completely fresh install with everything wiped.