I had a fault where one of the connections on the opposite end to the led arrangement had failed. It happened while I was using it and I think it was likely a poor connection to begin with and under a high load condition it has let go completely. In my case the fuse link that Collins showed was still good and I accidently put pressure on the failed connection when the battery was upside down and resting on the test button. It started to light up as I was poking around and led to me to the dodgy connection. Soldered back on and good as new.
The symptoms in my case was that it would not operate the trimmer or show any charge with the test button. It also tried briefly to charge and then would cut out suddenly.
