You can look into battery problems using the "BetterBatteryStats" app. There's various internet postings about this, checking how much your battery goes into "deep sleep" state, and finding out which apps and settings are keeping your phone awake (using battery) when you're not doing anything. That is, if re-doing your settings after the update doesn't fix it, and a factory reset doesn't help. I went through all my settings after the JB update, and found several that were reverted, or set to more power-consuming settings than I wanted. I didn't need to do a factory reset to normalize my battery usage as a result of fixing my settings. A couple of settings that come to mind are the "Maps" app having "report my location" on, and having 4G/LTE on (which I never use because it sucks battery, I'm in an 4G/LTE fringe area). If your settings are okay, generally speaking one or more apps is misbehaving, and causing your phone to be using battery when it shouldn't be. BetterBatteryStats gives you a way of finding out which apps are the culprits, and taking care of business.