Forever to Charge - What's This?

[jviss]

Update:

I turned off the charger yesterday, around noon or so, I don't remember exactly when. The basement really smelled of sulphur, and the batteries were boiling over (venting) even though I had only enough water in them to cover the plates when I started.

Now, at 8:00 a.m., they are still bubbling(!), and they sit at 12.79V.

I don't know what to think.

I think I will:

1. separate them, i.e., break the parallel connection;
2. clean up! Water with baking soda and lots of paper towels;
3. measure specific gravity in each cell;
4. see if I can equalize them with the power supplies and/or chargers I have - not sure any of them can put out enough current to get them 16.2V (Trojan's recommended equalization charge voltage);
5. test capacity with my load tester, at the 20 hour rate.

180W Constant Current Electronic Load 200V/20A Battery Tester Discharge Capacity

I also have an Argus AA500 which I can first use for a quick test.

I'm thinking I may have shorted cells, from sulfation, which is preventing a full charge, i.e., letting the current drop off; but that doesn't explain the voltage lever seen this morning. I am assuming the equalization charge may be able to blow the sulfation shorts, but I am not sure about this. And, if so, once done what will the battery's capacity be?

Thoughts?

 

[jviss]

Update:

3 days later!!! - and I haven't done any of those things in the list, but the batteries are still making bubbling sounds, and still sit at 12.7V!

 

[Davidasailor26]

Update:

3 days later!!! - and I haven't done any of those things in the list, but the batteries are still making bubbling sounds, and still sit at 12.7V!

Free energy!

I hadn’t realized you had them in parallel when you were first charging them. I’d try charging each separately and see if one goes to float properly. It’s possible you have a short between two cells in one battery, sucking current and keeping the charger in absorption. If that’s the case the other battery should charge normally when separated. Although a short like that doesn’t really explain why the battery still rests at 12.7.

 

[DArcy]

If you haven't already, separate them, let them settle then measure voltage on each battery separately.

 

[Hayden Watson]

Just guessing but given that they are still bubbling, I suspect that one cell in one of the batteries has a short and the other battery is functioning more or less correctly. The resting voltage of a good FLA is about 12.9v. They have 6 cells so that comes to 2.15v each. If the bad battery is only running on 5 cells its resting voltage with 5 fully charge cells would be 10.75v.
Because those 5 cells are being pushed to 12.7v each cell is seeing a charge voltage of 12.7/5 = 2.54v. If you put 2.54v into a 6-cell battery that would be 2.54vx6= 15.24v. So basically, one good battery has been equalizing 5 cells of the bad battery. Because the voltage is so high, the internal resistance of the cells is also quite high so it takes very little current to keep the five boiling but once the good battery runs out of capacity, it will go downhill quickly.
Seperate them and charge each individually. Then you could take them down to your local auto parts store and have them to test them.

 

[jviss]

Then you could take them down to your local auto parts store and have them to test them.

Thanks for the thoughtful reply. I have some pretty good battery testing gear, though, including a programmable load tester. I'll use that and report back.

 

[Tally Ho]

Update:

3 days later!!! - and I haven't done any of those things in the list, but the batteries are still making bubbling sounds, and still sit at 12.7V!

Perpetual energy devices!

 

[LouisMK]

In my experience (3 boats) cheap batteries are a false economy. If you do your research you’ll find that sizes are not alll typical & I think there are some which can lay on their side. If you change battery chemistry (AGM, etc.) remember you’ll also want to change your starting battery to match or risk ruining it when charging.

 

[Hayden Watson]

Thanks for the thoughtful reply. I have some pretty good battery testing gear, though, including a programmable load tester. I'll use that and report back.

What happened when you separated them?
What was the resting voltage for each?
Have you tested them separately?

"Inquiring minds need to know"

 

[jviss]

What happened when you separated them?
What was the resting voltage for each?
Have you tested them separately?

"Inquiring minds need to know"

So, as of about an hour ago, they have been separated, and both charged, and both got down to about 2.5A charging current at 14.4V before I stopped them, and they are both sitting at about 12.9V resting. Weird. I am re-reading the instructions for my load tester, watching an old movie on TCM, and having a Scotch as we speak.

I plan on cleaning up (the acid boiling over) then load testing them.

Please rest assured, I will tell all when I do these things!

 

[cagreen75]

I have over the years experienced many problems with batteries, especially older batteries, where they seemed to be ok after long periods of charging only to leave me stranded without power shortly afterward. Granted these were mostly car batteries, but a battery is a battery in my book, and batteries that are showing their age always give you warnings before they leave you without power. For me instead of trying to get more life for a battery when it starts showing signs it is dying I just replace it. While that may sound like I am jumping the gun before proper charging followed by testing I have found that doing all that is usually a waste of time and I end up with a new battery anyway mostly because I no longer trust it. But that is just me trying to avoid stressful situations. I'm not saying that a battery can't be brought back to life through proper charging, I'm saying I personally don't bother with all that.

 

[jviss]

Well, @cagreen75 I hear what you are saying. I'm just trying to see what I have, and then make a decision. I'd like to get another season from these, as I'm watching my overall budget. This pair were almost $500, and they are "only" 3 1/2 years old.

I have a good load tester, so I can see how they do under a 20 hour rate test. They have been sitting over a day at 12.8V each, after a difficult charging process.

I really don't want to invest in any more lead acid batteries, so if I can squeak by on these, I can look forward to a LiFePo4 system in 2023.

 

[cagreen75]

Well, @cagreen75 I hear what you are saying. I'm just trying to see what I have, and then make a decision. I'd like to get another season from these, as I'm watching my overall budget. This pair were almost $500, and they are "only" 3 1/2 years old.

I have a good load tester, so I can see how they do under a 20 hour rate test. They have been sitting over a day at 12.8V each, after a difficult charging process.

I really don't want to invest in any more lead acid batteries, so if I can squeak by on these, I can look forward to a LiFePo4 system in 2023.

For your situation, I understand your thinking, but in the interest of not ruining a trip, I would replace the batteries. That said, with proper care and maybe close attention to the batteries you can probably get through another season. I personally wouldn't take that chance. I wish you all the best and am hopeful that your not-so-old batteries will serve you well until you can replace them.

 

[jviss]

Resurrecting this old thread with an update.

Scrapped those batteries. Trojan SCS200's are backordered 'til July or August and, yes, $263 each. Due to timing and budget I decided to revert to the tried and true WalMart Everstart Deep Cycle batteries - two 27DC's for the house, and a 24DC for the start battery, also a deep cycle, BTW.

Weight: 51.4 and 43.4 lb. for the 27DC and 24DC, respectively. I recall that the SCS200, a group 27 deep cycle battery, was 60+ lb.

I managed to get really fresh batteries - date code 4/23, so manufactured this month!

So, here we go again.

What's the maximum charging current for these? I can't find a spec for that. I will go with 15% of capacity unless I hear different. C is 109Ah, so for a two-battery parallel bank I'll limit it to 33A. Stil looking for the battery temp sensors for my ancient charger.

The 24DC should easily start my Mitsubishi-based 4 cylinder, 38HP Westerbeke, and also be an O.K. backup for everything else in case the main bank fails.

Also planning on installing low-voltage disconnects for the fridge, main panel, or some combination of things.