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50Kwh AGM Battery bank

mig6116

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Oct 31, 2022
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Hi There, My name is Mike, and im reaching from Mexico

I have the need to build a offgrid system, i will use 2 Growatt SPF 3000 inverters configured in parallel mode, and for them i need to have a 50kw AGM Bank, this is 40 12V 110Ah AGM Batteries, at this time i cannot go with LIPO batteries because of the high cost of them, so the only way is to get AGM´s

I plan to use 2 4S5P arrays, and then connect them im parallel, but im not quite shure if this is the best way to achieve a good result on battery life , also plan to use a Battery equalizer/balancer as the HA02


the connections im thinking of will be like this this is a 4S4P array, any thoughts?

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Best case scenario, four strings will be extremely difficult to balance. I had a 24 volt system with four strings and it required constant attention. Your wiring diagram is going to leave the two strings in the center under charged most of the time. I used this method and it helped but was still not easy to keep balanced.
 

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Best case scenario, four strings will be extremely difficult to balance. I had a 24 volt system with four strings and it required constant attention. Your wiring diagram is going to leave the two strings in the center under charged most of the time. I used this method and it helped but was still not easy to keep balanced.
Yes i know it is difficult and also we are talking there would be not four but five strings, and then parallel this with another five string set, as i need to get to 50kwh goal i dont see any way how to get there, of curse were talking a 48V system here, the use of a HA02 per string (10 units total) will help to get the packs balanced it think...
 
The balancers won't be able to give those agm's an *initial* good charge. This very first charge is extremely important as agm's need time to get that last 1% of charge in - something you cannot hurry and balancers using solar-only won't do it properly.

Since you are spending so much already, get a handful of 30-40A chargers to do this job first before you place them into parallel / series service.

Not initially charging an AGM *individually* well (ensures internal balance of those series connected cells), is a major contributor to starting out on the wrong foot.
 
Typically with Lead-Acid ( which AGM is ) you get bigger, single cell batteries, not parallel smaller batteries.


They have up to 2500 ah @ 2V and then put a single string in series.

5 strings of AGM's will just end up as trash and wasted of money, they are not intended for the purpose you are suggesting
 
Exactly. Always reduce your cell-count by getting the largest capacity you can, either singly in cells, or in overall battery count.

Because of the location, having a properly sized array to keep the agm's happy shouldn't be a problem, but you can't wing it. Have to do a tight power-budget. Daily-cycling is easy. Stay in absorb until the sun sets. Other threads for that.

But sometimes you gotta' "run what you brung", or is available. But I'm with you. Crowns have served me well.
 
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Another benefit of single cell installations is that if a cell goes out, adjusting your operating voltage by about -2V usually means you can continue operating while waiting for a replacement cell.

If longevity is your goal, AGM is not the right choice. Well maintained flooded will outlast AGM by 2X.
 
Instead of puting all 5 strings in parallel, run each 48 volt string to buss bars. this is what I did with my AGM,s (3 strings of four with HA02 per string) and the charging was much better.
 
Yes i know it is difficult and also we are talking there would be not four but five strings, and then parallel this with another five string set, as i need to get to 50kwh goal i dont see any way how to get there, of curse were talking a 48V system here, the use of a HA02 per string (10 units total) will help to get the packs balanced it think...

I have used the HA01 balancers in a 24v setup with good success, I imagine the HA02 will be good for 48v
 
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