I have the same light from Aldis with the same problem, but it work OK, so I just charge it for a few hours when it starts to lose power.
What I'm struggling with today is trying to work out which charger is the right one! Can you look at yours and tell me what the output is? I have two almost identical chargers and one says output 300 and the other 500. Just in case it matters, it would be good to know which one is the right charger.
Thanks!
Jenny, May 2012