A Sharing moment.
I have had a problem with my Tom TOm 710 for some months now. I have sent it in for repair and each time it comes back it works for 1 trip then dies again. After its 3rd return journey I bought new mains and car chargers. Same problem and I was getting the battery level display on it while I was driving, giving the indication that it was not if fact charging. In talking through the problem with the very helpful seller it turns out that the replacement chargers were not up to the job. NB They have to be 5volt and 2 amp... watchout for some chargers as the ones I bought were only 0.5amp which does not charge the battery on the 710. I like some others had assumed that it was a TOM TOM problem, given we had new chargers...
Hope this helps