I tested two different battery eliminators, the Bat-pac and the White Brothers. Both work well, but the the White Brothers is slightly better at idle. I think it stores more charge, because the horn sounds the same at idle or full throttle, whereas the Bat-pac yields a slightly growling horn at idle. For those considering purchasing a Bat-pac, I would advise against buying it directly from the maker's website. I did this, and never received my item or replies to my repeated emails. I've launched a Paypal complaint against him. He sells on eBay as well, and is having an increasing number of complaints about the same thing. I ended up buying one from a friend who had never used it.