Regards problem in my device

When ever I used to restart my BlackBerry device battery level goes suddenly down upto 5-10 %. For example If I restart my device when battery is full after few seconds it goes to 93 r 92 %..
Does the problem was with my phone or with my battery?? Can anyone help me??

Posted via CB10

you might have to calibrate your battery. But restarting a phone uses a lot of juice as well.