Almost 3 years ago I swapped out my 12V battery for two 6V (Trojan T-105) batteries. Last weekend, I noticed that my trailer was losing power really fast after charging up. I used a volt meter and discovered that one battery was reading ~4 volts and the other was reading ~6 volts.The water level looks to be fine on both.Is it possible that one battery is just bad? Is there some other issue I should look for? Should I just replace the bad battery, or do I need to replace both to keep them approximately the same age?

Almost sounds like a cell in the battery is dying

Know anyone who could bring over a charger capable of doing an 8v equalization charge? Or if you have a 12v Battery Tender you can possibly use that on the single 6v.

I believe you have happened upon the very rare situation where your GC2 has a shorted cell.Check your warranty but I think you need a replacement.

wopachop wrote:Know anyone who could bring over a charger capable of doing an 8v equalization charge? Or if you have a 12v Battery Tender you can possibly use that on the single 6v.Are you saying that the method of charging the battery can impact the length that the charge will last?

As mentioned above you might have lost a cell. You can try what's called an "equalization charge" and see if the bad battery can still be used. Wonder if the possible bad cell actually looks different if you shine a flashlight at night down the water holes.

One 6V battery discharging really fast | Good Sam Community

RichieW13
Explorer
Dec 11, 2020
capacitor wrote:
https://www.youtube.com/watch?v=9g1xLnFsob0Could be the way you put them in parallel.

I'm running the 2 x 6v setup, so mine are actually in series.
capacitor
Explorer
Dec 11, 2020
Ahh, my mistake! Sorry
BFL13
Explorer II
Dec 11, 2020
RichieW13 wrote:
Almost 3 years ago I swapped out my 12V battery for two 6V (Trojan T-105) batteries.

Last weekend, I noticed that my trailer was losing power really fast after charging up. I used a volt meter and discovered that one battery was reading ~4 volts and the other was reading ~6 volts.

The water level looks to be fine on both.

Is it possible that one battery is just bad? Is there some other issue I should look for? Should I just replace the bad battery, or do I need to replace both to keep them approximately the same age?

No mention of an hydrometer!!!!

Absolutely must dip an hydrometer into all six cells to know what is really going on.

Say you are into the green on all three of one batt, but only on two in the other batt. Now you must decide whether to to get one new 6 or two new ones.

IMO it would depend on how many cycles the "good" battery has done and what its SG is on the three cells. If almost as good as new I would keep it and get one new one. Or if not, not.
wopachop
Explorer
Dec 11, 2020
I guess he could grab his multimeter and some baking soda water.

Pop the caps and probe the battery acid. Dont forget to neutralize the battery acid on the probes with baking soda.
pigman1
Explorer
Dec 11, 2020
You need a way to check the batteries under load. It doesn't have to be precise, but I've been using one of these Load checker on the farm and on 3 RV's for years. Definitely not as good as a battery shops carbon pile checker, but it's never failed to tell me when I have a bad battery, especially when used to compare with others in the string. I carry one in the rig all the time.
jkwilson
Explorer II
Dec 11, 2020
wopachop wrote:
As mentioned above you might have lost a cell.

You can try what's called an "equalization charge" and see if the bad battery can still be used.

Wonder if the possible bad cell actually looks different if you shine a flashlight at night down the water holes.

I would not try to equalize a battery with a shorted cell. It likely has a mechanical failure which is very likely to create a spark which is a very bad thing with battery cells that are being overcharged. A cell adding no voltage to the battery doesn’t indicate a charging issue, but rather an electrical short.
RichieW13
Explorer
Dec 11, 2020
Update, FWIW.

I towed the trailer home on Sunday night, so presumably the batteries were charged then. I disconnected the batteries on Sunday night. So no use on the batteries for ~4 days.

Just now I went and tested the batteries. Good battery had 6.22 volts and bad had 6.08 volts.
pianotuna
Nomad III
Dec 11, 2020
Possibly time for new jars. Look at SiO2 chemistry.

You may wish to try to equalize since the "bad" battery did take a charge and hold it for 4 days.

It won't hurt to equalize both batteries which may make your life easier.
MEXICOWANDERER
Explorer
Dec 11, 2020
Batteries that are physically dropped especially tall ones like gc220 and L16 can suffer a damaged plate stack and fail prematurely. If the unit is of pre envelope era dendrites can form and short the stack. No matter what, you are facing a "blood pressure" of 30 over 10. The vendor I serviced carbon pile tested every battery received. Adequate voltage but insufficient amperage failed the Trojan and back it went to Santa Fe Springs. He wasn't in business to lose money.
time2roll
Nomad
Dec 11, 2020
RichieW13 wrote:
Just now I went and tested the batteries. Good battery had 6.22 volts and bad had 6.08 volts.
That is a lot different from the original post.

With this data I might try a 6v charger on the single battery. Possibly the battery retailer could help. Need to charge in conjunction. with hydrometer readings to give better indication of the condition.