TTv3 now wont turn on at all

my tom tom one v3 i think (about 2 and a half years old)had intermittent charging type probs in car and cutting out then needed to reset to get it started again. 30 mins later it turned of and then couldn't re-start even with any amount of resetting. plugged into pc and it fired up (several days later) worked for 5 mins then switched of by itself never to start again. have 2.6v at the battery could the battery be the prob or the charging circuit in the unit itself?