Bubbling batteries at rest

gicamuci · January 8

Is it normal that lead acid batteries at rest, are making a bubbling sound from time to time ?

BB. · January 8

What is the battery voltage and temperature?

One site has a formula/chart for gassing voltage vs temperature (I did not realize that gassing voltage was that temperature dependent):

https://eepower.com/technical-articles/gassing-voltage-in-battery-charging-mitigation-strategies/#

Image: https://eepower.com/uploads/articles/gassing-voltage-in-battery-charging-mitigation-strategies-fig1.jpg

Nominally, Lead Acid batteries are best charged between 25C and 35C... and gassing would start around 14.4 to 14.1 volts at that temperature range.

Ideally, you do not want fully charged Lead Acid batteries to gas when "floating"/not charging/not EQ charging. Uses water, heats battery, and increases corrosion and plate shedding. All are not great for battery life.

Bubbling during end of charging cycle and EQ charging--Some "Fizzing" is OK as it helps "stir" the electrolyte (helps prevent stratification of electrolyte) and shed "sulfated" (no longer active in charge/discharge cycling) plate materials.

-Bill

gicamuci · January 12

Thanks Bill.

I have 16 Dyno D90 batteries in 8s2p strings for 400Ah @ 48V bank.

I also have some relays in combination with a Tuya device that follows the sunrise/sunset to "cut off" the batteries after sunset unless there is no power from the grid.

So they are just sitting all night, truly resting, no charging and no load.

In the morning, before sunrise I can hear them bubbling from time to time.

I am afraid they steal current from each other.

BB. · January 12

If one bank had a shorted cell (or two), then that bank could be charged by the other parallel connected string(s).

A very nice debugging tool is an AC+DC Current Clamp DMM (digital multi-meter)... Just set the function and clamp over one wire/cable and read the current.

A couple of examples... One inexpensive, one "mid-priced" unit:

https://www.amazon.com/UNI-T-Digital-Handheld-Resistance-Capacitance/dp/B0188WD1NE
https://www.amazon.com/Auto-Ranging-Resistance-Klein-Tools-CL800/dp/B019CY4FB4 (more functions, higher current clamp range)

A quick way to see if you have current going from one bank to the other at night.

Note there are AC only current clamp meters too--They are great for measuring AC current flow--But won't work with DC circuits.

Obviously, you could also disconnect one string at a time and see if you still get the bubbling. Also, you could measure each strings' resting voltage (typically at least 3 hours of no charging/no discharging).

Other things to look for--Is one battery bank getting warm/hot during charging? Again, a shorted cell would divert more current to its bank and possibly over charge (and would reach gassing voltage sooner during voltage while the other string is still slow charging).

When batteries gas, the cells can trap the gasses under the plates--That could be slowly bubbling up--Or if there is some vibration in the floor in the morning (or this bank is in a moving vessel/etc.) vibration and/or a little tilting could dislodge some gas bubbles too.

Do you have a hydrometer to measure the specific gravity of each cell? (assuming these are FLA batteries). Just to make sure all battery cells state of charge are equal (within 0.015 to 0.030 SG units).

https://www.solar-electric.com/midnite-solar-battery-hydrometer.html
https://www.amazon.com/s?k=hydrometer+battery+acid

Make sure to rinse the hydrometer out after you are done--The dried electrolyte can get sticky. Also, for glass hydrometers, make sure you set them on something so they don't roll off the table and break.

Just taking some guesses here...

-Bill

gicamuci · January 20

Thanks Bill.

I have all the tools you mentioned.

And indeed the batteries are sitting at around 25C or above during the night. I am on an island in the Caribbean.

Cheers,

Alex

BB. · January 20

Alex,

Did you figure out if one bank is (with a shorted/low voltage cell/battery) is "charging" from the "good string" of batteries overnight?

-Bill

gicamuci · January 21

I am not sure yet. I measured each of the 16 batteries voltage and there is a variation of 0.1 to 0.3 volts. Not sure if that's a lot or normal.

I have to make some time to measure each cell SG.

gicamuci · January 25

Post #2 appears to be true. This morning the temperature "dropped" to under 24C and the bubbling appears to be less.

boB · January 26

If you have access to a FLIR or other thermal imaging camera, you can see if there is one battery getting hotter than the others.
This can be a great indication of problems. That is, aside from voltage being at Absorb or above.

Never did hear what your battery voltage was in the morning when you hear the bubbling.

boB

BB. · January 27

And it would be per battery (or per cell, if you can access single cells) voltage...

-Bill

gicamuci · January 28

I have this infrared thermometer:

https://a.co/d/0Hd0TMG

Though I can only test for temperature per battery, not per cell.

I'll let you know.

Temperatures are set to drop further more this coming week, to around 20C in the morning.

Bubbling batteries at rest

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