question

FRA avatar image
FRA asked

Sulfation or stratification (flooded start battery?

I used classic cheap flooded starter batteries in solar light cyclic application (95 ah maintenance free but not vrla). 
I noticed this phenomenon: every month or 2 months of light daily cyclic use (DOD 15% and subsequent full recharge), the real capacity tends to decrease quite, Let's say 10% after 1 month and 20-30% after few months, even if it gives a false Open circuit voltage of 13.1 v. 
However, an equalization charge at 15.0 v for 1-2 hours, and consequent bubbling of the electrolyte, restores the correct full capacity for the next 1-2 months. The strange thing is that the equalization only works if I previously discharge the battery with at least 30-40% dod. While it is less effective with dods below 20%. 
What is the cause of this periodic behavior? 
I thought of slight sulfation or stratification of the electrolyte. But none of these things should happen, as the batteries are charged every day and they move and shaking with the motorhome. The problem happened at the same way with 3 batteries from 3 different brands and it seems to happen only to me. The charging and discharging parameters have always been the same: average dod 15% and complete daily recharge with absorption of 14.4v 1-2 hours and temperature compensation -18mV / C and floating 13.8v. I am afraid that the periodic equalizations will dry the electrolyte that cannot be refilled because they are free from maintenance, even if they are classic flooded. 
Using agm deep cycle batteries this phenomenon has never happened to me and the capacity remains constant over time for the years of use.

What is the cause?
Why does equalization work so much better with previous heavy discharge?
battery chargingequalisation
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3 Answers
Eduard avatar image
Eduard answered ·

Periodic EQ will do the batteries good. Most people are against EQ, but i believe it is important to lift the voltage on a frequent basis. Most of the sealed batteries are sealed only up to the label, pull it of and most batteries have plugs, fill water then if you see it is low. Lastly my opinion is that this is a short life battery, install AGM or if you have sufficient funds then go for lithium.

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Thanks for your opinion ...
This is just a battery that I use alternately (unfortunately, even removing the label it is not possible to remove the cover ... I tried but the cover itself is damaged)
Actually I have already bought a victronenergy deep cycle 110 ah agm.
It works very well ... However, after a month I have a very similar phenomenon.
If I do microcycles continuously (DOD 5% -8%), the voltage seems to decrease slightly (0.05v ... I am writing down the smartshuunt data daily ... VOC for each DOD).
But then, with the first DOD over 14%, with standard charging without equalization, the original voltage is restored.
How do you explain it?
In literature, AGM batteries ARE IMMUNE FROM STRATIFICATION.
Also in the literature (dozens of technical texts) I have never found that microcycles worsen performance.
Likewise I have never read about the "memory effect" in lead acid batteries ....
Yet, by now in 4 batteries (flooded and agm) I noticed this:
- medium cycles (DOD 15% -40%) maintain full VOC and full capacity.
-Repeated micro-cycles (DOD 5% -8%) reduce vov and capacity, much in flooded, little in agm.
It looks like a little memory effect !!

Anyone have a similar experience ??
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H.W.Oelofse avatar image
H.W.Oelofse answered ·

From the behavior you are describing it indeed seems like you will be experiencing the effects of stratification. There is a need to stir up the electrolyte and the equalisation charge will achieve this unfortunately the effect will in long term be loss of electrolyte and ultimately failure of the battery excessive equalisation can also cause shedding of the active material on the plates. In the past I have physically agitated flooded batteries to mix the electrolyte up.

1 comment
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Thanks for your opinion ...
This is just a battery that I use alternately.
Actually I have already bought a victronenergy deep cycle 110 ah agm.
It works very well ... However, after a month I have a very similar phenomenon.
If I do microcycles continuously (DOD 5% -8%), the voltage seems to decrease slightly (0.05v ... I am writing down the smartshuunt data daily ... VOC for each DOD).
But then, with the first DOD over 14%, with standard charging without equalization, the original voltage is restored.
How do you explain it?
In literature, AGM batteries ARE IMMUNE FROM STRATIFICATION.
Also in the literature (dozens of technical texts) I have never found that microcycles worsen performance.
Likewise I have never read about the "memory effect" in lead acid batteries ....
Yet, by now in 4 batteries (flooded and agm) I noticed this:
- medium cycles (DOD 15% -40%) maintain full VOC and full capacity.
-Repeated micro-cycles (DOD 5% -8%) reduce vov and capacity, much in flooded, little in agm.
- in flooded start batteries, equalization combined with a previous average discharge (DOD 20-30%) generates a large increase in voltage (up to voc 13.4 v) and what appears to be a decrease in internal resistance.
This improvement only lasts 4-6 days.
It looks like a little memory effect !!
In any case, to restore capacity periodically, a heavy discharge and subsequent full recharge seems to have more effect than a simple equalization charge without a previous heavy discharge.
Again, none of the dozens of technical texts and datasheets and tests I have read report similar effects.

Anyone have a similar experience ??
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FRA avatar image
FRA answered ·

Thanks for your opinion ...

This is just a battery that I use alternately.

Actually I have already bought a victronenergy deep cycle 110 ah agm.

It works very well ... However, after a month I have a very similar phenomenon.

If I do microcycles continuously (DOD 5% -8%), the voltage seems to decrease slightly (0.05v ... I am writing down the smartshuunt data daily ... VOC for each DOD).

But then, with the first DOD over 14%, with standard charging without equalization, the original voltage is restored.

How do you explain it?

In literature, AGM batteries ARE IMMUNE FROM STRATIFICATION.

Also in the literature (dozens of technical texts) I have never found that microcycles worsen performance.

Likewise I have never read about the "memory effect" in lead acid batteries ....

Yet, by now in 4 batteries (flooded and agm) I noticed this:

- medium cycles (DOD 15% -40%) maintain full VOC and full capacity.

-Repeated micro-cycles (DOD 5% -8%) reduce vov and capacity, much in flooded, little in agm.

- in flooded start batteries, equalization combined with a previous average discharge (DOD 20-30%) generates a large increase in voltage (up to voc 13.4 v) and what appears to be a decrease in internal resistance.

This improvement only lasts 4-6 days.

It looks like a little memory effect !!

In any case, to restore capacity periodically, a heavy discharge and subsequent full recharge seems to have more effect than a simple equalization charge without a previous heavy discharge.

Again, none of the dozens of technical texts and datasheets and tests I have read report similar effects.


Anyone have a similar experience ??

2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.