flat battery

My mate who a m800 left his heated grips on and flattend his battery. He jump started it from his car, now he has the dial going around and the Fi light coming on and off.
Any ideas would be great

sorry don't really know errrmmm maybe he could check that he connected the battery back up properly and everything is tight the light might be coming on and off coz there is a lose connection or it could just be that the battery has had it and the bike is picking up on that might need a new battery?

Thanks for your reply. Dead cell in the battery was the problem

Could it be a dead cell in the battery?    I never knew that would make the FI light flash? Interesting to know