AGM battery bank "bubbling" noise

[sprinter99]

Hi

I have a 1.1kw battery bank that consists of 8 12v 141ah C&D technologies UPS batteries. They are wired in 24v. They always "bubble" when they are close to fully charge and in absorption mode on my Victron CC. I read online that the only thing that makes agm batteries bubble is overcharging ? I have them set up on my victron as 28.2 absorption and 27.6 float. What am i doing wrong ?

 

[Hedges]

If disconnected and left for a few hours, what is the resting voltage?
If one cell was low, then others could overcharge and bubble.

I haven't noticed noise from my AGM but I'm not usually around them.

https://cdtechno.com/wp-content/uploads/2020/05/12_1029_MR_0915.pdf

"Recommended Maximum Charging Current Limit C20/5 amperes @ 20hr rate"

"Float Charging Voltage 13.65 ± 0.15 VDC average per 12V unit" (27.3V in your case)

"Equalize charge and cycle service voltage 14.40 to 14.80 VDC average per 12V unit"

1) It doesn't mention absorption charge. Maybe you should just float charge.
2) What is your charge current?

My guess is they don't want 14.1V per cell on a regular basis; that's half way to equalization voltage.
(Assuming I found the correct battery and instructions)

 

[Supervstech]

How much amperage are you pushing?

 

[sprinter99]

If disconnected and left for a few hours, what is the resting voltage?
If one cell was low, then others could overcharge and bubble.

I haven't noticed noise from my AGM but I'm not usually around them.

https://cdtechno.com/wp-content/uploads/2020/05/12_1029_MR_0915.pdf

"Recommended Maximum Charging Current Limit C20/5 amperes @ 20hr rate"

"Float Charging Voltage 13.65 ± 0.15 VDC average per 12V unit" (27.3V in your case)

"Equalize charge and cycle service voltage 14.40 to 14.80 VDC average per 12V unit"

1) It doesn't mention absorption charge. Maybe you should just float charge.
2) What is your charge current?

My guess is they don't want 14.1V per cell on a regular basis; that's half way to equalization voltage.
(Assuming I found the correct battery and instructions)

I had agm before this set up and never heard any noise as well. The max charge current is 60a.

Usually around 25.6 resting voltage.

So would i just set up my absorption set up at 27.3v ? Because with my victron I am pretty sure I have to put a number in the absorption phase.

Thanks for your help

 

[Hedges]

I had agm before this set up and never heard any noise as well. The max charge current is 60a.

"Recommended Maximum Charging Current Limit C20/5 amperes @ 20hr rate"
I think that says max 0.2C
You have 141 Ah wired 2s4p, 564 Ah and 60A charge rate for 0.104C, so good.

Usually around 25.6 resting voltage.

So would i just set up my absorption set up at 27.3v ? Because with my victron I am pretty sure I have to put a number in the absorption phase.

Thanks for your help

Yes, I would set both absorption and float for 27.3, because that seems to be the one and only charge voltage given.

I've often seen two different charge profiles, one for cyclical and another for standby. But this battery only quotes the one.
Concern of course is if your battery won't get fully charged this way, which shortens life.
Mine have absorption voltage and time, but also a preferred charge rate. Mine have an alternate absorption time for low charge rates.
I'm

"Designed for UPS Standby Power Applications."
Not even intended for cyclical, don't know how long they will last or if a different charging profile would be better.
These batteries are optimized for carrying high loads for a short time, spec'd for discharging to a cutoff voltage in 5 minutes to 90 minutes.

 

[HRTKD]

If the array of eight batteries are not configured in a balanced layout, one or two of the batteries could be getting the bulk of the amps, while other batteries are getting much fewer amps.

My two Trojan T-105 6v batteries would have a faint gurgle to them when under charge. I always thought that was normal.

 

[Hedges]

For the Trojan FLA, bubbling would be normal because electrolyte is liquid and charge current supposed to be high enough to keep it stirred.

Trojan Battery | T-105 6V Flooded Battery

The T-105 6V deep cycle flooded lead acid battery provides rugged durability and features T2 Technology for maximum sustained performance, longer life, and increased total energy.

www.trojanbattery.com

AGM charging should minimize gas production, but it will have catalyst for recombination.

Good point on balanced layout. I think his batteries are 2s4p, so perfectly balanced is possible but you have to realize that is desirable and do it deliberately.
His charging is nominally 50% of spec, so very poor balancing of interconnect might exceed current spec.

 

[svetz]

I always thought that bubbling was hydrogen, which would be split from the water in the electrolyte, which would mean it would be bad as you're depleting electrolyte which can't be restored.

 

[Hedges]

I always thought that bubbling was hydrogen, which would be split from the water in the electrolyte, which would mean it would be bad as you're depleting electrolyte which can't be restored.

Both hydrogen and oxygen are released. In a battery, not necessarily lost.

VRLA battery - Wikipedia

en.wikipedia.org

"Under normal operating conditions the gases can then recombine within the battery itself, sometimes with the help of a catalyst, and no additional electrolyte is needed."

 

[Supervstech]

I always thought that bubbling was hydrogen, which would be split from the water in the electrolyte, which would mean it would be bad as you're depleting electrolyte which can't be restored.

As long as the battery remains sealed, the electrolyte can recombine. Of course, if it vents, like in a FLA battery, it is gone.