Son , do you have this model ? 200.71222[IMG]
It is a very common Sears Diehard Automatic battery charger. This is not a battery maintenance charger, which is what you need for long term , walk away battery maintenance. Battery Tender , floating charger is what you need for maintenance. The Diehard will not shut off when the battery is fully charged and if left on in that condition can damage your battery.
The Sears Diehard Automatic charger 2/10/50 is to be used ONLY on LEAD - ACID batteries , NOT Gel or AGM.
Do you have the Sears battery charger manual? PM me if you need one.
To slow charge a low battery at 2 amps , I've never had problems just connecting the charger to the in car battery while cables are connected. But with 10 amps , I disconnect negative battery cable before charging.
You can make the negative charger connection at either the battery terminal or engine/ frame., but I personally connect to the terminals. Always connect the negative last and disconnect first to avoid a possible spark as a matter of practice.
No , you will not lose your tune.