Quick update. Managed to download the instruction manual and try a few different settings but with no success. Still getting the "battery high voltage error" message.
Switched to my old quad charger (the one where the displays have dimmed to the point they are barely legible) and that charges fine. So it's obviously something that's gone wrong with the GT Power charger. Still fine for LiPo, just not for 4 cell NiMh
