I swear by battery tenders. Been using them for over 20 years with a lot of good luck in extending my battery lives. Especially for these expensive repro batteries. Around 5 years ago my AGM yellow cap repro decided to buy the farm. My conventional tender wasn't helping it hold a charge. I put it on my regular charger to see if I could bring it back too and no luck. After I found out they weren't making the repro's anymore I did a hail mary and picked up a Pulsetech Xtreme Auto Charger after hearing a lot of good things about it. To my complete surprise it brought my battery back and it's been working great for the last 5 years. The Xtreme is a fantastic one that desulphates and there are other new ones as well that have algorithms that accomplish the same thing. I'm a believer now.