Kyocera 902kc overheating and draining battery fast

I bought a used Kyocera 902kc and replaced the battery on the phone with a brand new one, but the phone gets very hot while charging and during use. In 3 hours, 'system' used 18% and apps used 31%, but it doesn't specify all my apps. The sum of all of my battery usage from apps only totals to 13%, so I'm not sure where the remaining 18% is going? Is it possible to get more in depth battery usage info, and has anyone had any experience with something like this?