It’s really weird, I know the batteries are wired correct, the cables are labeled from the factory by skeeter. The trolling motor is unplugged. The charger is off. But as soon as I touch the battery terminal with the charger wire, get a spark and blow the in-line fuse. I tried doing positive first, negative first, putting on both and then putting the fuse in, keep getting a spark and blowing one of the fuses. I could see a short making it not charge or the trolling motor not work, but this is making a spark as soon as I connect the 4th wire. Sometimes it will spark when I touch the negative and blow the fuse on the positive terminal.