What he said. I have an Optimate 3 and charge via a Powerlet port that I installed as an un-switched outlet via a PC-8 fuse block. The Optimate should come with a battery harness with it's own connector, mine did. That works very well too. I have three ends that plug into the Optimate III. One is alligator clamps for a plain battery. One is the pigtail for the battery that was supplied, and the third is one I ordered extra with the powerlet port plug. Love the Optimate. Great quality and has kept a FJR battery alive for 160k miles and 7 years. Worth every penny of the cost.