I have one, that came from walmart. I would have to go to the garage to see the brand name it is. I don't remember the cost, but I think it was around 50.00 its about 6"x4" and about 2" thick. keep it connected all the time, when i'm not fishing. my batteries stay full charged. I've used it for 2 years on a waverunner and my boat, never hurt my batteries or never had a problem with it. works great.