I was charging yesterday at a rapid charger. It got to 94% and then realised I was going no higher. The charger had stopped and unlocked the lead. I thought nothing of it but the car would then not restart. Tried switching it on and off a few times then realised that the 12 Volt battery was showing 12.2V not its usual 14.2V. Eventually had to call the AA who charged the battery and everything was fine again. The AA man tested the 12V and said it was working fine so no idea what went wrong. Strange that it wouldnt work even at 12.2 V . I was not draining the 12V when waiting in the car. Anyone any ideas as to what happened and how to prevent it in the future ?