Originally Posted by FlaRider
I should have said they are Harris AGM batteries in a 2018 DSDP
Some may make way more technical arguments, but I will put it in plain English. Your entire battery bank will only be as good as the worst battery .
The P.O. replaced one battery between the time I purchased it and picked it up. I donít know why he felt it failed but he did. I have 3 12v flooded wet batteries.
I was having trouble going overnight without the voltage going low enough to shut the inverter down. Tv, fridge and a laptop. 480 watts total. Since I only had 2 nights without shore power I left it alone until I got home this spring.
I pulled all 3 out, charged and tested them with my computerized tester. The new one checked out at 100%. The other 2 20%. I put the one new one back in and I had more amps/time with one good one than with 2 bad and 1 good.
I replaced all 3. Bought 3 identical 120 ah flooded at Samís on sale for $68 each.
The only proper way to test batteries is to disconnect each, put a charger on them and test with a good battery tester. Checking voltages even across one battery will give wired readings. You may test one at 6 or 12 volts, but if connected to one with a bad cell one connection may only show 4 v
And just because you have voltage doesnít mean you have amps. Wit 8 6v batteries like you have, if they are all good and fully charged you should get 2-3 days drawing 200 watts.
I know a lot of coaches and a lot of people like using 6v golf cart batteries, I have found 12v deep cycle battery to work as well if not better. Remember, if you buy 6v 120ah batteries and put them in series you still only have 120ah, at 12v I find golf cart batteries just as much as a similar size 12v battery. So why buy 8 when you get the same power out of 4. Plus a lot less cables and less chance to make a mistake.
Find an old 12 v battery, wire just 1 positive and one negative, hook to shore power, so your converter has something to keep 12v on while you charge and test all your batteries. If you find one dead, itís time to replace them all.