question

francesco avatar image

New victron agm battery accurate solar charging parameters

Hello I just bought a victron deep cycle 110 ah agm to replace the old battery after 3 years.
I would like to ask a Victron technician for the correct parameters.
I only use a solar charge with a fully configurable 30A mppt regulator.
Every day the solar energy is more than enuff to charge completely the battery. 
I discharge the battery every night on average about 20 ah.
I would like to know the correct absorption voltage and the correct duration of the absorption for my use (daily discharge of 20 ah).
Currently I have set 14.5v and absorption duration of 120 minutes with temperature compensation of - 4mV / C / cell. Floating 13.7v.
Today for example after the end of the absorption, the battery absorbed 0.8A in floating at 13.7V.
But trying to increase the floating to 14.5v, I saw that it went up to 2.6A. These is strange for me... 
Does that mean it wasn't fully charged? Or is it due to gas generation?
Then disconnecting the solar panel, after an hour the battery was at 13.5v, so it would appear to be fully charged.

The old agm, at the end of absorption, absorbed 0.8a for both 13.7v and 14.5v.
Why these difference on new battery? 
I can see all these parameters on the victronenergy smartshuunt.
MPPT - Solar Charge ControllerVRMchargingAGM Batteryabsorption
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2 Answers
Paul B avatar image
Paul B answered ·

I have attached the full data sheet for you as well

1618025640563.pngDatasheet-GEL-and-AGM-Batteries-EN.pdf


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thank you very much ... I had already read that document. but it says 14,2-14,6 .... what do I put exactly? Is 14.5 a good compromise for my light use? and the floating? what do i choose between 13.5 and 13.8? 
Regarding the absorption time, I would like to manually copy the algorithm of the smart solar charger, i.e .: 
11.9V <Vb <12.2V 4h 12.2V <Vb <12.6V 2h Vb> 12.6V 1h. my solar mppt charger epever tracer does not have the adaptive function, but I have to set the time manually. usually my battery in the morning is always> 12.6, so 1 h. 
is it useful to do a light refreshment \ equalization once a month? I was thinking like this: discharging the battery to 50% and charging at 14.9v for 2 hours? or is it harmful or useless?

for me if you have the batteries in a HOT area/climate then use the lower voltage settings.

you DONT equalize AGM or GEL batteries EVER


the more cycles the battery do the more harm is done

im in a mid-hot area but i have temp compensation for -4mV \C\cell or -24mV\C like victron reccomend in your datasheet.

My battery make 1 light cycle(from 10 ah to 20 ah) each day, and every early morning is from 12.6 to 12.9v, before the controller start charging.

I fear to overcharge the battery with tomuch absorbtion time, and i copy manually the algoritm of victron smart solar mppt: 1h absorption time with batt>12.6 v, 2h with 12,2v<batt<12,6v. Instead, my mppt controller,by defoult would do 2 h absorbtion each day

These is ok???


Ok , like you said i eliminatethe equalization 1 each month.

francesco avatar image
francesco answered ·
thank you very much ... I had already read that document. but it says 14,2-14,6 .... what do I put exactly? Is 14.5 a good compromise for my light use? and the floating? what do i choose between 13.5 and 13.8? 
Regarding the absorption time, I would like to manually copy the algorithm of the smart solar charger, i.e .: 
11.9V <Vb <12.2V 4h 12.2V <Vb <12.6V 2h Vb> 12.6V 1h.
 my solar mppt charger epever tracer does not have the adaptive function, but I have to set the time manually. usually my battery in the morning is always> 12.6, so 1 h. 
is it useful to do a light refreshment \ equalization once a month? I was thinking like this: discharging the battery to 50% and charging at 14.9v for 2 hours? or is it harmful or useless?
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