I'm getting ready to head south for a few days fishing. I charged my battery up to 100% the other night. I had my depth finder on for about 15 minutes the other night and I plugged the charger in tonight and it said 60%. So I charged it up again to 100% and it didn't take long at all to charge. About an hour later I plug the charge in and it says 85%. The battery is 3 years old.