bubbling sound when charging VRLA AGM batteries - Page 1
Forum section: electronics / general

author: Freesurfer
author_rank: Regular Contributor
timestamp: April 28, 2019, 02:25:44 am
content: I've been given 30x VRLA AGM batteries of 12V/40Ah each which I have recently installed for an off grid solar system. They have been sitting unused, stored on a pallet outdoors for 5 years without any maintenance charging. The cardboard was somewhat moist and the terminals had some light corrosion. The datasheet specifies a 10-12 year service life design. I didn't expect the batteries to be in great shape considering they need a continous trickle charge of 13.7V for maximum service life, but I thought I'd give them a go. When I unpacked them and checked the voltage with a multimeter, they were all in the 12.4-12.6V range, with an exception of 2 batteries in the 11.x V range which I discarded. "Not bad at all" was my first thought. I topped up some of them with a charger, and I have had 8 of them power 400W of light for around 8 hours without issues. I only tested the load until the battery voltage dropped to around 11.3V, as lead acids shouldn't really be that deeply discharged. They also accept a charge fine, and after a full charge, they come down to a resting voltage of 12.8-12.9V.But I have noticed that when I charge them, there is a little bubbling or fizzing sound coming from them. It sounds a bit like a glass of coke sitting on a table. Based on the research I have done, this is supposed to be a bad thing on sealed batteries as excessive bubbling will cause the cells to vent and dry out with no way to replace the water. I have noticed this when charging with a regular 12V/4A battery charger (charging 4 batteries in parallel), and with a solar panel charging 2 in parallel at around 3A (1.5A each). I have heard this sound both during bulk charge while the battery voltage is <13.7V (when gassing shouldn't happen), and when they are at the topping charge cycle at 14.4V.Is it normal for VRLA batteries to make any sound at all? Or is this a bad sign? Or could it be because they have been sitting around for this long and that the bubbling will stop after a few discharge/recharge cycles? Or could it be that they seem fine for now, but will die after a few cycles? VRLAs are supposed to have a catalyst which will recombine any oxygen and hydrogen that has gassed. But I cannot find any info whatsoever about what rate the catalyst is able to recombine the gas back to water. Or any info on whether or not the fizzing sound is normal or due to unwanted gassing.I am also a little worried about the cheap chinese solar charge controllers as they seem to leave the batteries cooking at 14.4V for longer than they should. The controller has an option to select between "Sealed" (14.4V), "Gel" (14.2V) and "Flooded" (14.6V). So I decided to switch from sealed to gel, but the display still shows 14.4V on a sunny day.Is anyone experienced with VRLA batteries?

author: Freesurfer
author_rank: Regular Contributor
timestamp: April 29, 2019, 02:21:05 pm
content: Thanks for your response.I am fairly sure the voltages are reasonably accurate. The controllers have an LCD displaying the voltage. I have 4 controllers in total (each charging 2 batteries in parallell. Those pairs of 2 are then connected in a string of 4 in series for a total of 8 batteries)When I compare the voltage on the controllers' display with the multimeter, the controllers all report the same voltages as the multimeter. The controllers only have 1 decimal digit showing for example 14.4V, while the multimeter has 2 digits, like 14.40V, but the readings are reasonably close. And even if I haven't checked if the meter itself is good, I'd be surprised if all the controllers are equally inaccurate and the meter also happens to be equally bad :-) But I will bring another meter just to be sure, but my main suspicion isn't on inaccurate readings.Also regarding the wiring itself, the charge controllers are all floating relative to each other with no common ground, and each controller has its own solar panel with The panels or controllers are not connected to each other or sharing any wires anywhere so I am 100% certain there is no current accidentally bypassing the controllers' cutoff.Also, the bubbling noise doesn't only happen at 14.4V near the end stages, but also early during the charging process when the batteries certainly aren't full. The charge process may be in in the range where the terminal voltages are 12.5-13.2V, charging at a rate of about 3A (approx 1.5A for each battery). The bubbling can still be heard.

author: paulca
author_rank: Super Contributor
timestamp: April 29, 2019, 02:39:26 pm
content: Can you take the charge controllers out of the equation and connect a current limited power supply (Or 12V battery charger) across the batteries at 14.40V and see if you still hear bubbling?It would at least focus the issue on the batteries and remove the charge controllers from suspicion.

author: Freesurfer
author_rank: Regular Contributor
timestamp: April 29, 2019, 02:53:02 pm
content: The same thing happens with a 12V 4A battery charger. Even when I had 5 batteries in parallel.

author: mvas
author_rank: Contributor
timestamp: May 10, 2019, 05:12:05 pm
content: After sitting for 5 years, the batteries are probably heavily sulfated.AGM Batteries self-discharge at ~2% per monthSo, after sitting for 5 years the State-Of-Charge was ~30%You state, the batteries are out-gassing when Bulk Charging and the voltage is still less than 13.7 Volts.That is bad, very bad.That loss of water is permanent.The "... 10-12 years service life ...", that you quoted from the datasheet, does not allow for 5 years of sulfation due to non-use.Who is the manufacturer?Lifeline has one of the best warranties, only Pro-Rated for the first 5 Years then nothing, because they know how long their batteries will lastWhat is the warranty for these batteries?The warranty will tell us more about their expected life, than anything else.