The guy with the Harley. It sounds like he left the battery in the bike during storage. Big mistake. For storage over the winter I pull my batteries, bring them inside where the temps stay above freezing. I don't leave the chargers on full time. I rotate around.
Try to charge each one every month or so.
Lots of people think the $10 trickle chargers are good but very seldom are. They can overcharge a battery because they use the batteries internal resistance to control voltage. They often have a 800 milliamp output but the voltage can reach 15 volts or more. A trickle charger is ok to use but not hooked up indefinitely they don't shut off. Hook it up, charge say over night, unhook, test battery voltage. If still low another night. Test and repeat as necessary to reach full charge.
Once charged stop charging.
Leo
Try to charge each one every month or so.
Lots of people think the $10 trickle chargers are good but very seldom are. They can overcharge a battery because they use the batteries internal resistance to control voltage. They often have a 800 milliamp output but the voltage can reach 15 volts or more. A trickle charger is ok to use but not hooked up indefinitely they don't shut off. Hook it up, charge say over night, unhook, test battery voltage. If still low another night. Test and repeat as necessary to reach full charge.
Once charged stop charging.
Leo