Bad battery or something else? topic

I have a GT-P3113 {stock 4.2.2 I think} (and have the OEM cord and wall charger) it was collecting dust while I was toying with my chromebook..well today I plugged her up (@ the time completely dead)when the battery was @ 50% I unplugged did the update package that was available and when it went to reboot...it didnt. It jus acted like I had plugged it in while it was off..so I checked the battery stats [pic below] jus a massive battery drain or something else any help or anybody else having this problem

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