When you say it was reading a bit over 11v, that's DEFINITELY low.The very minimum needed is 12.5v, and I'd be much happier seeing high twelves or low thirteens. As a check to see if the battery's ok, give it a low charge (my battery tender gives 0.75A) When it's charged, leave it for at least half an hour, then check the voltage. The GZ hasn't got a great charging system, and low voltage is the cause of a lot of problems that folk ask about, on this site.