I have a standby generator with a small car battery to start it. I added a trickle charger to keep the battery charged. The battery finally gave out after 10 years.

The trickle charger was overcharging the battery which caused the bolt on the battery clamp to corrode. I assume the battery clamp is lead. I cannot for the life of me get the corroded bolt out. Any suggestions to get the corroded bolt loose? I am replacing the battery charger with a better one that should only charge the battery as needed so it won't overcharge.