been there and I can tell you only about my own experience I bought a so called better battery odyssey 680 and researched the battery tender business I found most are made in china with the same schematic inside but with different cosmetics so basically same stuff. I tried several and the end result is they all worked fairly well I currently removed my battery from the cold weather and keep it tendered in my basement connected to a CTEK float tender for gel pack battery ,the charge is regulated and the battery is perfectly maintained I think keeping the battery out of the cold has a higher impact than the choice of tender keeping in mind the style of battery you acquired