I picked up one of the small ones the size of a thick, full sized phone. Didn't even know the technology had gone past the massive versions from years gone by. I did it because I never got around to adding my second battery to my boat as the wiring and modifications for the blue sea systems add a battery switch were more than I have ever had time to deal with which doesnt comport with my upgraded sound system. Never used it yet and so I tossed it into my car just In case for the winter here in Minnesota. The videos of the number of vehiclea it can start are kind of surpprising. Diesles, v8's, it doesn't matter.