When to replace 6v batteries

Good for you. Yes, four gc2 are a good way to go. I started with a similar set up and 520 watts of solar. When I added a resi frig I added another bank of 480 watts of solar.

We try to boondock as much as possible and spend months in the desert. Have you looked at freecampsites.net and campendium? They are good sources.

On our trip now, made it to Iowa and for our dry CG ive got 2 new CG2 in my battery bay and 4 6v in the bed of my truck that are 4 and 6 yrs old..My DW loves lights so with this capacity see can leave them all on, But in all our years of travel we just never stayed at any Nat, State or County CG with our dogs, now that their gone (I miss my little friends) we decided to try it out..once out of the N.east they are great, big with 30/50a and cost that helps stretch our cash..Now I found so far for the Montana to do a few days of dry camping its best to have 4-6v CG2 batteries, this is with my 350w of solar it allows me to not have too worry about the batteries or lights.. The CG2 battery is a very durable that will last for many yrs just got to watch the water level

Just to be safe, stopped at sam's club a picked up 2 Duracell GC2 6v batteries for 85$ ea, Not bad, there sitting on the charger now and will test them tomorrow..Its amazing how well GC2 will last with proper care, the battery bank I have a home has my very 1st set of GC2 batteries I bought 12yrs ago to power our battery/inverter backup system...Thanks to all

Yes we should all find some poorly charged batteries that were chronically under charged and barely used so they could slowly be preserved in their sulfates.

OP seems to be charging correctly and has rather low resting voltage. Although the more recent post the battery seems to hold 12.5 pretty solid.
Hard to know without the history.

I would tend to run the batteries until they come up short to where I expect them to perform. Worst case OP could spend a day and pick up new batteries on the road.

I got six Trojan Gc220 batteries in Santa Rosa Ca. For the price of the cores. The needed desulfation badly. The owner grinned as I paid him 60 dollars and carted them off. Here five years later they are still going strong in rancho Arce Arce. He used the money saved to buy more panels snd a battery monitor.

BY
THE
WAY

Those batteries were rescued in 2012. The owner said they were six years old and "never worked right". Had a head as dense as a brick. Keep laughing...

Whimsical "Oh today, I am going to decide they are bad" is a personal inviolate choice. Just let me know if you decision is based on whiffenpoof. Bad batteries do not test good. So-so batteries do not test good. Batteries with a year's service do not test "good". Seems testing is now obsolete.

Guesswork! The mark of somone with money to burn...

One thing that influences my choice in these situations is how heavy those suckers are and how hard they are to move around. If we're trying to squeeze a few more questionable years out of them, when I could just put brand new ones in there and be done with the potentially damaging physical labor. That's my perspective anyhow. I'm late for that global warming parade! :)

Good luck to you Rich. You are going to love that vacation, as those spots are some of our favorites in the country. If you catch the pull-off on the north side of the Yellowstone Canyon around 10:30, you'll see the falls with the rainbow this time of year. Safe travels and may you leave your battery troubles in NJ.

I ck the post and yes I'm using my old rv batteries as a power backup at the house for when the power goes out during the winter months, I keep them charged and yes they work well for what it is...now in my 5th wheel.. im typing sitting here in the camper at Englishtown,NJ at raceway park for there summer Nationals...dry camping batt. voltage is 12.5v lights on,some led, other half not, tv on 12v, this montana is a power hog, especially when my wife camps with me but drag racing isn't her thing...so are they weak? don't know until the morning after needing to use the heat going down to low 50's well its 58' now...see its not the 12.5v it will be the capacity they have.. now why I asked this Question..Leaving fathers day for a 6week vacation into the Rockies, From Grand Teton to YellowStone To Glacier then into Alberta,Canada following rt93 into the (Ice Feild Pkwy) Baniff NP upto Jasper and back down then to the UP of Michigan ...Bucket list vacation for us...THERE WILL BE MUCH DRY CAMPING thats why I asked to see what type of answers to my post I would get..On the roof sits 350watts of solar panels@ 24v and a Outback solar controller 60amp...Thank you for your Answers and tell you how I do at E-town with my batteries

It doesn't cost anything to equalize the batteries, a load test is free also. My 2 6v Sam's Club GC batteries seemed to not hold a charge over the winter and being 9 years old I was going to replace them, but I ran an equalizing function first then a desulfate function for 24 hrs and they are holding a charge well. My starting battery was slow to turn over the engine but was a maintaince free battery so I could not equalize. I took it to Walmart and they load tested it and it was only putting out 590 CCA's It was rated at 770 when new, it was 9 years old also. So I bought another one rated at 810 CCA's at Walmart. You have nothing to lose by trying to equalize first.