Victronenergy AGm deep cycle performance and boost voltage

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Fra asked Dec 8, '21

Victronenergy AGm deep cycle performance and boost voltage

Hello, I have a 110 Ah Victronenergy AGm deep cycle, from April 2021.
-It is managed by a 30 A epever 3210AN mppt charge controller. With a 300 watt panel.
-It is discharged daily on average of 15 / 25AH, which is with DOD 15/25%, which is ún SOC 85/75%.
- has about 260 cycles
- it is recharged to 100% every day (in the Canary Islands the sun is good even in winter) with the parameters of the victronenergy datasheet, boost 14.4v, float 13.8v, temperature coefficient - 24mV / C, boost time 1-3 hours .
- once a month I do a slight equalization at 14.7v 3 hours.
-I collect all data from victronenergy smartshunt and epever module for statistics, in particular I record the open circuit voltage every night after discharge.

I noticed that for the first 2 months the ocv for each SOC rose slightly.
Instead, since November, I have noticed a drop in ocv for each SOC of 0.07v.

For example after a discharge of - 12AH before it had ocv 12.88 / 12.91,
now after a discharge of - 12ah, it has an ocv of 12.82 / 12.85v.
At 100% before it had an ocv 13.20 / 13.25v, now it has an ocv 13.12 / 13.18v.

Instead the capacity remained the same.
Only the ocv dropped by 0.07v.

I did dozens of tests and collected the ocv after 30 minutes of the discharge 270 times, every night.

Do you think this is normal?
Could it be the temperature?
From April to October the battery was discharged at around 26/28 degrees Celsius.

Then I have another question:
The victronenergy datasheet says: boost 14.2-14.6v.
What does it mean?
I am using 14.4v because I have done various tests with smartshuunt and between 14.4v and 14.6v, the current does not change. So I prefer a not too high boost voltage.

I'm doing well?

The Rolls battery technical service told me that I'm wrong and that I have to recharge with boost at 14.7 v and fixed boost time of 4 hours independent of the DOD. Otherwise my battery will sulfate in less than 12 months.
He also claims that the victronenergy adaptive boost time is not good, because the boost time must always be the same, regardless of the DOD, because it always serves to recharge the last 20%.
But I prefer to follow the victronenergy datasheet.

Could the 0.07v drop in ocv be a sign of sulfation?
(I don't believe because the capacity hasn't changed)

MPPT Controllers battery charging AGM Battery

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2 |3000

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michelg commented · Dec 08, 2021 at 08:27 PM

Hi Francesco, not sure if Victron AGM batt. are Rolls or not, but if you have been in touch with Steve H. be sure that he knows what he is talking about.

Michel.

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Fra commented · Dec 09, 2021 at 09:41 AM

Thank you michelg... Yes, is Steve Higgins. Victronenergy aGm are not Rolls products.

I think victronenergy agm have a thinner plates of Rolls agm.

Certainly rolls technical service is competent.
But what it says is different from what the victronenergy datasheet says.

What do you think about my question?
Is a 0.07v drop in ocv normal in 7 months?
Yesterday I did a dod of -24 ah (20% DOD).
The battery had a 12.61v ocv.
With the same dod, until 2 months ago, it had an ocv of 12.69v.

It's normal? Is it the lowest temperature? Is it sulfation?

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michelg Fra commented · Dec 10, 2021 at 01:19 PM

Sure, temperature is a factor, I see differences between the seasons, and how hard I use them or not... Proceeding once as Steve did recommend won't hurt the batteries, aand it may also show that it has a problem.

I would follow his advices and recommendations.He knows pretty well all the circuit from batteries up to inverters, including mppts. He was working at outback power in the past.

Michel.

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Fra michelg commented · Dec 14, 2021 at 11:29 AM

Hi, thanks again for your reply.

Yes I did as Steve said. I did a 3 hour abs for 3 days, the tail current does not drop below 1.4%.

I did not notice any difference in the subsequent discharge between a 3 hour abs and a normal 1 or 2 hour abs.

Do you have agm batteries? Do you use a fixed abs time, or a DOD dependent abs?

Thank you

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