My Cells Are "Gurgling"

[alcook62]

So, this has happened to me twice. I was standing next to my three paralleled batteries, and they started to make this sound like "gurgling." The first time I heard it, I initially thought, "Oh, my stomach is vocal." After a second or two, I realized that was not the case, and it was from my batteries. Same the second time, and it continued for nearly ten seconds. I recognized the sound and went to remove the cover, however the sound stopped before I could remove it.
I've looked through the search functions here and Googled the symptoms and found nothing. Has anyone else experienced this? Thoughts?
The cells have not experienced any bloating/swelling, they have been pampered and never over or undercharged.
Edit: These are LiFePO4 cells in an 8S3P setup.

 

[solarHandyman]

wow. What brand of battery? What vendor?

 

[timselectric]

That's not normal, at all. I'm suspicious that it's even possible for LFP. There's very little liquid in them.
I would shut it down, until I figured out what's going on.

 

[Brucey]

Edit: These are LiFePO4 cells in an 8S3P setup.

I would check the voltage of every cell.

 

[AntronX]

Show us what your pack looks like. Which cells? Do you smell anything when opening the cover? Electrolyte has distinct sweet smell.

 

[OffGridForGood]

agree with above plus question: does this happen (only) at high state of charge?
what is the max voltage setting in your system?

 

[sollap]

Sound can be confusing. I'd recommend putting some heavy blankets or something absorptive around those batteries and then listening again. Given that they're LFP, I'd bet that gurgling sound is coming from something else.

 

[v_green57]

Since your battery bank is composed of individual cells, you should be able to take a big screwdriver (or something like it) and listen to each cell by putting the handle end of the screwdriver against your ear, then CAREFULLY placing the tip end on the top of each cell - well clear of the terminals just to be safe.

Unless you already have one of those "mechanic's stethoscopes" laying around:

https://www.harborfreight.com/mechanics-stethoscope-63691.html

in which case you can do this in style...

 

[OffGridForGood]

Funny story time:
I had a bad idler on the hemi one time (ok more than one time) so there are two identical idlers and when the part came in I couldn't remember for certain which one had the bad bearing. So I get the mech stethoscope and start up the truck, my wife was watching and saw me listening to something in the engine bay. I didn't notice her at the time - I was watching to be sure I didn't get wacked by the Rad Fan blades...
So I locate the bad bearing and swap it out with the new one.
Restart the truck and no screeching sound now.
At supper she asks me if my hearing is going - what ? no, why would you ask?
Oh I saw you needed a doctor's stethoscope just to hear that fan-belt screaming, that I could hear clear across the yard - she says!

okay back to the OP's thead...couldn't resist.

 

[outsider]

Even better than the screwdriver is a length of tygon tubing, maybe 3 or 4 feet long and a quarter or a half an inch in diameter. Stick one end in your ear, and explore around with the other end. It works much better than you would think based on this description. You can localize the sound to an inch or less. Try it with something like a ticking watch (if you have such an antiquity) to be amazed by how well this method actually works, and then try it with your batteries.

Incidentally it is useful to localize the source of corona discharge in high voltage circuits, though, this is probably not such a common need in solar circuitry.

 

[shvm]

Check cell voltages.
And dial in your charge settings such that per cell voltage is not over 3.55 V
This factors in some margin for cell imbalances.

 

[alcook62]

I would check the voltage of every cell.

Cell voltages are all well within specs. Both times were during charging, however. I only charge to 3.5 volts.

Show us what your pack looks like. Which cells? Do you smell anything when opening the cover? Electrolyte has distinct sweet smell.

I've never smelled anything. There is no sign of any disturbance regarding any of the pressure-release valves. All cells are flat and even.

I would shut it down, until I figured out what's going on.

I'm fully off-grid, miles from a pole, and reluctant to shut down before fully identifying the problem.

I will continue to observe and listen to my batteries for the next couple of days, especially at the end of the charging cycle. Both times this happened, it sounded a lot like my old lead-acid batteries bubbling during peak charge voltage. It only lasted mere seconds, just long enough to locate the area where

Check cell voltages.
And dial in your charge settings such that per cell voltage is not over 3.55 V
This factors in some margin for cell imbalances.

I don't charge over 3.5 volts per cell and have no issues with cell imbalance. My JBD-based Overkill BMS's passive balancer

I'd bet that gurgling sound is coming from something else.

This could be. I will continue observing/listening and try to eliminate the cells as the source.
has dealt with any potential issues.
the sound was coming from.

 

[timselectric]

Use a piece of tubing, as described above. It will help you easily narrow down the exact location of the sound.

 

[740GLE]

We’re cells at 3.5v when you heard the sounds

 

[alcook62]

Use a piece of tubing, as described above. It will help you easily narrow down the exact location of the sound.

Yes, I'll do that. Doubtful I'll do it today, though, it's raining and not likely to get close to a good charge.

We’re cells at 3.5v when you heard the sounds

I'm only guessing at this point but probably close to that. I was watching the absorb stage as I wanted to see how my new Midnite DIY charge controller played with my original Midnite 200.

 

[alcook62]

Show us what your pack looks like. Which cells? Do you smell anything when opening the cover? Electrolyte has distinct sweet smell.

This is with the cover off. Unknown which battery/cell was making a sound.

 

[740GLE]

I have that same hummingbird feeder!!!

 

[Skypower]

No visible leakage
No smell
No swelling (not fixtured, multiple charges!)
Low delta at full charge?
If so;
I’d not be too concerned about the noise but inspect daily for a while.

 

[Daddy Tanuki]

up looks tidy I would just watch it closely the next couple of days... set a webcam or an old camcorder on it and let it record while you are doing other things.

 

[alcook62]

No visible leakage
No smell
No swelling (not fixtured, multiple charges!)
Low delta at full charge?
If so;
I’d not be too concerned about the noise but inspect daily for a while.

That's an affirmative on all the points you've mentioned. I will be watching and listening toward the end of the absorption cycle for the next few days. I've taken the advice of @timselectric and @outsider and procured a length of hose to use as a stethoscope. It's amazing how well this simple thing works!

and let it record while you are doing other things.

What other things? I'm old late middle aged and retired. This will be the highlight of my afternoon!

 

[Daddy Tanuki]

That's an affirmative on all the points you've mentioned. I will be watching and listening toward the end of the absorption cycle for the next few days. I've taken the advice of @timselectric and @outsider and procured a length of hose to use as a stethoscope. It's amazing how well this simple thing works!

What other things? I'm old late middle aged and retired. This will be the highlight of my afternoon!

So you have the same issues I have I gather.... I wake up with wood and my wife tells me to put that damn thing away before i break a hip....

 

[alcook62]

So you have the same issues I have I gather.... I wake up with wood and my wife tells me to put that damn thing away before i break a hip....

Hers or yours!!

 

[Daddy Tanuki]

Hers or yours!!

Me, she is 10 years younger so at 47 she is still sturdy.

 

[alcook62]

Well, no more guessing. I've conclusively identified the bad cell. Yesterday afternoon I found this:

 

[Skypower]

Well, no more guessing. I've conclusively identified the bad cell. Yesterday afternoon I found this:

Your hearing and instincts proved correct. Did it ever see over voltage? If it didn’t, what you have is pretty rare.