Sounds like your logic board is at fault. I can guarantee you have a bad capacitor somewhere causing a short between the +/- at the battery connector.
you can check this with a multimeter by connecting the first and last pin of the battery connector. If it has continuity then you have a short. You will have to take out the emi shields and find out exactly which capacitor is causing the problem. sometimes you can take out the circuitry from a battery and solder it to a dc outlet and find where it gets hot. Most of the time you can tell visually where the short is due to the corrosion