One 6V battery discharging really fast

[RichieW13]

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?

[pianotuna]

RichieW13,

The hydrometer is by FAR the best way to test for state of charge.

Hint--pinch the tube so the liquid stays in the unit.

What was the specific gravity reading in each cell of each battery?

Make sure you wear eye protection. Woolen clothes are good idea, too.

Since the batteries were 3 years old please reconsider only purchasing one.

[RichieW13]

Just an update of where I am.

I picked up a hydrometer and tested the batteries. (That seems like a fairly imprecise way of measuring things.) My weak battery was just measuring very low on the hydrometer. The good battery was a little strange. When I would fill the hydrometer, the float would quickly rise to the top, but slowly drop as the fluid leaked out the tube. But it seemed to be OK.

So I ended up buying a replacement battery for just the one weak battery. It will probably be a few weeks before I get to take the trailer out again and give it a good test.

[MEXICOWANDERER]

Voltage by itself is a useless value. A watch battery may have voltage but enough power to tickle a flea. No flooded battery in my memory (100,000+) has ever recovered from a sitting voltage of 1.33 volts per cell. It is far beyond the ability of a plate to absorb.

Battery manufacturers handle specialty batteries carefully
Trojan industrial batteries are handled with kid gloves. But golf car batteries are less carefully handled. One drop straight down onto concrete from 12" has a great possibility of demaninating plate separator stacking. WW II SUBMARINE batteries had porous material lining giant sediment chambers. Upon return to Freemantle, Pearl Harbor, or Mare Island, Gould and Exide would examine samples for delamination. Severe depth charging shock would fate all batteries for replacement. I visited the Exide battery shop on Mare Island in 1955 with my father. Loading batteries took like 40 people and senior machinery operators. Battery shock really helped sell spiral cell AGM batteries for off road racing.

[time2roll]

wa8yxm wrote:

time2roll wrote:
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.

Inclined to agree with all but one word "Rare" it's not that rare it is one of the more common failures.

for 12v RV batteries yes, don't hear so much about GC2 with shorted cells.

[Gjac]

We are all just guessing that you may have a shorted cell you won’t know for sure until you check it either with a hydrometer or multi meter like wopachop described. That is how I do it I have not had good luck with hydrometers. It is not uncommon as batteries age that some cells read less than others. Equalization usually fixes that. I have brought mine back several times using that function on my charger. Try the test first, if it is totally shorted it’s time for new batteries if one cell is low try to equalize it and see if it holds a charge.

[wa8yxm]

time2roll wrote:
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.

Inclined to agree with all but one word "Rare" it's not that rare it is one of the more common failures.

For the O/P. NEVER replace half a battery (one 6V) Always replace the full battery (Both of them)

[RichieW13]

time2roll wrote:

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.

The original problem was while camping, the lights in the trailer would start dimming about an hour after batteries were charged.

Holding a charge longer now, because batteries not in use.

[wopachop]

jkwilson wrote:

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.

Thank you!! I hope others catch this and read what you said.

[time2roll]

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.

[MEXICOWANDERER]

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.

[pianotuna]

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.

[RichieW13]

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.

[jkwilson]

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.

[pigman1]

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.