Back in the 90's I had to replace the Harley battery every year and I rode it weekly for most of the year. After about 3 times, I got sick of it and after reading a lot about how they work, I got a Battery Tender like the one pictured. The first time I got 3 years out of the same kind of battery with the same type of use. I was so impressed with how well it worked that I put them on everything I had sitting around and all the other bikes, cars, boats and other toys I was working on for others. I even gave these things as gifts. Later, when HD updated my battery to a gel type, I had to switch to a smaller Battery Tender that works a bit differently. Same GREAT results. Still using the type pictured on the boat and on the 68 vw bug battery sitting on the bench for 2 years during the restore. I dont remember any of what I read about them, how they work, and I couldnt carry a conversation about how batteries or tenders function. Maybe batteries have improved and that accounts for my results but I seriously doubt that. My opinion is just that and based on my own experience.