Is my 85amp leisure battery shot? Just replaced the 20 amp fuse which was blown, (don't know why it blew...) and found the battery voltage showed 3volts. Had it on charge for about four hours now, and it is now showing 9.6volts. What you think. The spec onnthe charger is 3.5 amps output so would this need a good overnight chrage to bring it up?