I'm not a pro here, but it is my understanding that it does not matter which way you go with hooking up the battery....pos or neg. The battery should charge irregardless which way it is hooked up, as current will follow the "open" door, so to speak. In other words, the battery will send current either way, if hooked up pos or hooked up neg. Now, with that said, I have listened to others share that it does matter when it comes to the coil....one indicated that you get twice to volts out of your coil if you have a pos ground verses a neg ground. You may have a drain on your system if the battery keeps going dead, but I don't think it has anything to do with the way the battery is hooked up. This question is a common question among antique car owners just getting started, or among older tractor owners. Good luck...(older cars were pos grounded)