@Antidean @Rivers or anyone else that may have knowledge, because I'm a moron about batteries.
My wife talked me into buying a new Icon electric cart 3 years ago. They came with six 8 volt AGM batteries that are supposedly no maintenance (don't need to add water, etc.) and the cart has an internal charger and we were instructed to leave it plugged in all the time. We only use it in the neighborhood, and after we got our pool last year we only take it out about once every 6 weeks on average. The other day we got it out (charger light indicated it was fully charged), but the dash display said battery was only 65% and it wouldn't go faster than 11mph. I drove it a couple miles then plugged it back in over the weekend. Now it says it's fully charged but the battery display says 28%. The Icon company won't respond to my questions, and the dealer I bought it from in Tomball wants to charge me an arm and leg for a diagnostic, then sell me either a new set of AGMs for $2500 or upgrade/convert to lithium for $3500.
I don't know if any of my description gives hints at what the problem is (infrequent use killed one or more AGM batteries? Defective charger?). Is converting it to lithium myself the best option, or is $3500 a good price to not have to hassle with it myself? The other consideration is since we stopped using it frequently, we could sell it and maybe upgrade to a Polaris/CanAm later for off-roading capability. I'm going to take a bath on the transaction since we bought new during late Covid at over $9k and I'd probably be lucky to get $7k with working batteries. If I go that route, do I buy "good" AGM or find the cheapest 8v lead batteries I can find and then sell it?