So, I have an old iPhone 4s running the last iOS (10.1?) and the battery drain is crazy, with some Chrome, Facebook app and Whatsup, I reach low levels after two hours, and I'm not a heavy user, every now and then I check messages, but it's not on all the time. I made some tweaks like disabling background refreshing, location and stuff like that, but it's still not helping. Now I'm thinking to buy a new battery, but before I buy one, I want to know how I can make sure if it's software or hardware problem. Is there anyway I can really check?