My son has two golf cart batteries from Costco in his travel trailer. One is dated February 2019 and the other April 2019. I took them out after being fully charged and had them load tested. They both tested OK. Prior to the test they had been fully charged with Solar.
An hour after the test the batteries read as follows: 6.34 volts and 6.48volts. 24 hours later completely disconnected they read 6.27 and 6.43. The older battery is the lower. He does not have a specific gravity tester, and I went to two places and both were out of stock. What is your analysis of the voltages after 24 hours? Water level is good. They went camping last weekend and the batteries went down pretty significantly during the night, but recovered with Solar during the day. Loads weren't that heavy. He has a trail manor travel trailer. The batteries have been deeply discharged once when he stored the trailer and forgot to turn on the disconnect.
Your last sentence says it all. Charge and record data to establish a pattern. If it went below 10.5, harm has been done, it not, it may recover after a series of charges.
Pierce
Thanks
There six volt right , I would be concerned with the oldest one with the lowest voltage.
I would do like mentioned and watch closely after a few charges.
I strongly doubt that Costco golf cart batteries are true deep discharge batteries so we might as well consider them starting lighting and ignition batteries. SLI batteries are made with grids filled with lead oxide paste. What happens when you fully discharge one of these batteries is the lead oxide sifts to the bottom of the case and when it builds up high enough it shorts the bottom of the plates.
True deep cycle batteries have solid lead plates and as such can't deliver the high current needed for starting an engine. But you can deep cycle them until there's no plate material left. Or they short internally.
Art Joly
Even though they are around 2 years old, just because they where deep discharged one time doesn't mean they are permanently damaged. As others have said try a few charge cycles. Of course we don't know how much load was on them overnight.
Both those 6 volt readings are good the higher one is very good.. Just double them and you have the equivalent of 12.54 and 12.86 on a 12 volt system. The lower one you should check again after another recharge.
Thanks. I'll run them through a couple cycles. These are Interstate 210 amp hour batteries. I would like to have a shunt style monitor to see where the power is going.
Just a little bit of a additional information.
The AiLi-Battery-Monitor-Voltmeter is showing a 7 -10 week delivery time per amazon.
The Victron BMV-712 Battery Monitor is a great meter, but at $206 it's at the high end of monitors.
You may want to check out the Renogy 500A battery monitor that has a lot of features for $97.
They are based based in Florida and amazon shows 3 day delivery. And they did!
Renogy is big in the solar market.
When you replace the COSTCO batteries, look at the Trojan T105 6 volt golf cart batteries. They are rated at 250ah.
If you treat they right, they should last 7-9 years.
Compare batteries at the 20 hr rating. The Trojan T105 wet cell batteries are rated at 225 amp hrs. AGM batteries might be a better (but more expensive) choice with less maintenance. Both require best practices for long life.
And to the best of my knowledge the Trojan battery line are the only solid plate deep cycle batteries around.
With wet cell batteries you need to do an electrolyte check. Check the specific gravity of the electrolyte. I don't know what would be for those but look it up. Then after making sure they're topped off with distilled water and with the caps off I would do a equalization run on them. This will bring them up equalizing and stress them a bit. Then let them sit and see what happens again checking specific gravities. Be careful when equalizing they'll get hot. Also watch for electrolyte coming out of the fill holes.
But I agree that the best thing to do would be to get rid of them and start over with something like Trojan t105's. You might be able to salvage them for a few more cycles but what cells do not like to be overly discharged it cuts their lifespan significantly.
Nothing wrong with wet cell batteries. But the amount of maintenance they require and the cycles that they give out in my opinion just not worth it. But they've been used successfully for many years on boats, RVs, trucks, etc.
Thanks for the help. Had to leave New Mexico for Texas to finish getting home on the market. Will send this thread to my son and he can make a decision. I found a load tester and retested the batteries myself. Results were good. Hopefully he can find a specific gravity tester to borrow. There were lots of empty hooks in the auto parts store's as evidently there is a supply chain slow down on restocking.
It's safer to top off the cells to just above the plates before charging as the liquid level will rise with the state of charge. Again, that's the mechanical action of the lead oxides accepting the charge. Then top off the cells to the full line with distilled water and give a 15 minute equalization charge to stir the electrolyte.
The care and maintenance of wet cell lead acid batteries isn't that big a deal if it's all you've known for 1/2 century.
If you have wet cells in a 98 coach the battery compartment is not vented correctly and a dangerous gas build can occur.
Earlier coaches had a battery tray with a lid that was vented to the wheel well area. Yours does not.
If you were talking about your sons trailer obviously that may be a different arrangement.