[QUOTE=halftone;4608465]If it's a non-sealed battery, check electrolyte levels - it could just be neglect of topping up for a year or two... But I strongly recommend you check the battery voltage with the engine running, using a multimeter.
This sounds very likely to be a regulator and/or rectifier problem with the alternator, and you are probably getting a high voltage sent to the battery, possibly AC. It should be 13.8-14.3v DC max.
Hi sorry for the post hijack, just checked my gt with engine running 14.28v does this point towards alt probs as mine drains the batt over a while as not used every day, will check fuses next.thanks in advance.