Firstly, 11.7 volts is storage level, your 3S battery should read 12.6 volts when charged (4.2 volts per cell) But that has nothing to do with your issue. Something in your connections is either connected in reverse or short-circuited. My guess is you have a short where the pigtail for your connectoe lead is soldered to the board. A couple close-up pics would help, but until you find the issue, DO NOT connect your battery again, you have a big risk of it exploding and burning your house down.