It'd be helpful if you could post some screenshots of your battery stats screens. Just because Android System is responsible for 50% of battery use doesn't necessarily mean it's using too much battery--for example, if you're not using much screen time (which is typically the biggest power drain), then other processes that would normally make up a lower
proportion of the battery drain are now responsible for a higher proportion. But if your battery life is still normal, then it doesn't really matter.
So see if you can give us info on what your total battery life is like, and your screen-on time.
In the meantime, check out some of these tips:
http://forums.androidcentral.com/am...how-tos/298919-guide-battery-saving-tips.html