Northstar Pure Lead AGM batteries are some of the best you can buy. 4 year free replacement warranty, not prorated, absolutely free replacement. They sure stand behind their product. I run 4 group 31's in my boat and have one grp 31 on my trailer, been flawless for me. AGM batteries self discharge at a far slower rate than Flooded Lead Acid batteries, charge twice as quick and can sustain many more charge/discharge cycles! Expensive but worth every penny, no brainer for me!
https://www.northstarbattery.com/product/nsb-agm31