Battery/brain Problems

The robot was working fine until I downloaded the 1.0.1 firmware, after that the battery randomly died so I pressed the reset button. As soon as I plugged the battery into the brain it turned off again, this kept happening. It should also be noted that, whenever I plug the battery into the brain, the brain says that the communication link need to update, but it turns off before I can do anything. The green lights on the battery have also gone very dim. I was wondering what I could do to fix this seeming as I don’t have my second battery yet to see if it is the brain or the battery that is the problem, thanks in advanced. I have also tried turning it on with no smart devices plugged in but it did nothing.