Originally Posted by ranger42c
Haven't ever heard of North State Batteries....
I think it is a distributor and not a battery brand.
All excellent advice on here. And I personally don't think 4 year old batteries should be considered at the end of their life. One of the best things you can invest in is a good battery charger. If you can find a 4 stage charger, that would be best. I know you will find a lot of 3 stage chargers. In a 4 stage charger, the 4th stage is "idle"...IOW, no charge is being put on the battery. The charger intermittently "tests" the battery and will put a float on it if needed. But having a float charge on your batteries continuously is not as good as having them at idle when they are fully charged.
And Listen to what Maerin said. That is excellent advice and an excellent post!!
My group 31 Odyssey AGMs are 2013 install and they are nowhere near the end of their life. My system theory is very similar to Steve's up above. I have 5 Group 31 AGMs for house AND start. And an isolated Optima GRP27 AGM for generator start. All maintained by a Magnum 2000w/100amp inverter/charger. I do have the original Charles 80 amp charger on standby if needed(it is usually when I make a mistake and that was only once). Another advantage with a charger like a Magnum is you can customize each charge phase to exactly what the manufacturer recommends...and not some "canned" charging profile that is simply "adequate".