bubbling/fizzling sound when charging my brand new AGM batteries

Thread Starter

BazsoDombiAndras

Joined Apr 26, 2015
65
Well, it's a question of point of view. I'd call a voltage of 13.65V a float voltage, since it's very low.
My charger does eventually switch to float (13.5V or whatever value I set for it) on most of the days (when there is enough sun to get there), but I think it switches to float because of the absorption timeout, not because it senses that the battery can't absorb enough power. I'm not entirely sure though.
 

takao21203

Joined Apr 28, 2012
3,702
Charging a battery with high voltage is bad.

Actually I have a modern electronic charger and a 12v 18ah battery and have done several cycles.

First the charger probes the battery for voltage. If it has less than 8v need to precharge with 2x 9v battery.

Then there are 3 programs

Motorcycle
Car
Winter

When I change to winter immediately, the charger will reach overvoltage.
Need to charge with lower current for some time first.

Then switching to winter, the voltage goes up first, then gradually goes down to 12.4 typically then charging for a long time.

If you reach high voltage fast and it doesnt go down your battery is defective!

So the max. current is 3.6A in the winter setting. But the charger doesnt just apply a voltage. It will check the voltage all the time and display it.
 

ronv

Joined Nov 12, 2008
3,770
Here is what I would try.
Set the charge voltage to 14.3 and the float to 13.6.
If the voltage is above 13.6 when they start bubbling your problem is the charger doesn't switch to float soon enough. (same problem I have, I think)
The charger should switch to float when the charge current is below 3 amps (battery is fully charged), but I bet you can't adjust that. :(
 

Thread Starter

BazsoDombiAndras

Joined Apr 26, 2015
65
ronv, I think you're probably right. Even if I set the absorption voltage to 14.3V (or whatever value), the charger should switch to float as soon as the batteries can't absorb more than 7.5A (0.05C). However it does not, because this value is fixed at 1A.

So the only solution I have found is to set the absorption voltage to 13.8V and the float voltage to 13.5V. This way they never bubble. The float voltage is OK, I think, but I fear that the low absorption voltage may cause sulfation. Hopefully it won't happen because if there's enough sunshine, the PV panels can keep the charge on for enough time for the battery to become fully charged even at these lower voltages. I hope...
 

ronv

Joined Nov 12, 2008
3,770
ronv, I think you're probably right. Even if I set the absorption voltage to 14.3V (or whatever value), the charger should switch to float as soon as the batteries can't absorb more than 7.5A (0.05C). However it does not, because this value is fixed at 1A.

So the only solution I have found is to set the absorption voltage to 13.8V and the float voltage to 13.5V. This way they never bubble. The float voltage is OK, I think, but I fear that the low absorption voltage may cause sulfation. Hopefully it won't happen because if there's enough sunshine, the PV panels can keep the charge on for enough time for the battery to become fully charged even at these lower voltages. I hope...
You might be able to build something to fool the charger. Don't know if you want to go that far, but it would be interesting to know the voltage and current when you first hear them start to bubble.
I know how you feel, I was very surprised that my charger couldn't charge my 125 AH batteries & yours are bigger. If the timer works good it may not be a big problem since they are so big.
 

Thread Starter

BazsoDombiAndras

Joined Apr 26, 2015
65
Yeah.. I keep hoping that the manufacturer of the charger (Victron Energy - serious company) will give in and allow this setting of tail off current to be changed.
The point where a very faint bubbling starts is somewhere around 13.8V and 6-8A, but I'm not entirely sure about this.
 

LMF5000

Joined Oct 25, 2017
130
@BazsoDombiAndras - I've read the whole thread and having the same bubbling noise with a brand new sealed deep-cycle AGM battery myself now.

Since this thread was started 5 years ago, how did you eventually resolve it? What kind of battery life did you get out of your bank? Still going strong after 5 years? It would be very enlightening to hear from you - this kind long-term test data is worth its weight in gold.:)
 

Marcos32

Joined Nov 16, 2021
2
I've used 3 different voltmeters + the charger's built in voltmeter, they all show the same thing.
Hello! I read all the post, and something like 6 years after your problem I'm EXACTLY on same situation with same fears and worries...4 12v 100ah AGM (2x24v serie/parallel) with same voltages and sounds.

I want to know if you ever fixed your problem, if your batteries still working and what happened into this 6 years xD.

Hope all fine,
bye
 

boostbuck

Joined Oct 5, 2017
501
I reread this old-ish post and I can't see any mention of temperature as a consideration.

Battery specs provide derating figures and graphs and define charge voltages as at 20C because battery temperature rise REDUCES the appropriate voltages for charge limits before gassing.

As well as ambient temperature affecting the process, batteries under charge will SELF-HEAT, which adds to the problem. A hot environment and a C10 rate could REDUCE the permitted maximum voltages before gassing by quite a lot. This is why chargers for large battery systems have provision for a temperature sensor to attach to the batteries.

If you don't have a temperature-compensated charger, then you should set your charge limit voltages to the appropriate values for the hottest likely battery temperature INCLUDING self-heating.
 

Marcos32

Joined Nov 16, 2021
2
I reread this old-ish post and I can't see any mention of temperature as a consideration.

Battery specs provide derating figures and graphs and define charge voltages as at 20C because battery temperature rise REDUCES the appropriate voltages for charge limits before gassing.

As well as ambient temperature affecting the process, batteries under charge will SELF-HEAT, which adds to the problem. A hot environment and a C10 rate could REDUCE the permitted maximum voltages before gassing by quite a lot. This is why chargers for large battery systems have provision for a temperature sensor to attach to the batteries.

If you don't have a temperature-compensated charger, then you should set your charge limit voltages to the appropriate values for the hottest likely battery temperature INCLUDING self-heating.

Me and the author of this post have around 15°C of battery room temp, so I don't think that this can be a problem, right?
 

boostbuck

Joined Oct 5, 2017
501
15C is will be fine if the cells don't feel warm when charging. If they do you might want to put a thermometer on them to check the rise is below 25C or so.

The last time I looked at damaged batteries they were in a tin shed at 35C ambient!
 
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