24 volt AGM battery pack configuration

My neighbor is running a battery bank consisting of 8 Powersafe SBS 190 AH 12 volt agm batteries. He has them wired in 2 banks of 4 batteries in parallel. These 2 parallel banks are then wired in series so there are 4 batteries on each side of the series connection cable.
Electrically this produces 24 volts nominal, which is what he wants, but I'm unsure if this is the best configuration for charging with 24 volts.
Will one side of the parallel pack get charged up before the other. I can see the positive side getting the leftovers from the negative side.
He has a 60 amp mppt charger.
I hope I am wrong here.

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Ironman said:

My neighbor is running a battery bank consisting of 8 Powersafe SBS 190 AH 12 volt agm batteries. He has them wired in 2 banks of 4 batteries in parallel. These 2 parallel banks are then wired in series so there are 4 batteries on each side of the series connection cable.
Electrically this produces 24 volts nominal, which is what he wants, but I'm unsure if this is the best configuration for charging with 24 volts.'

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Most manufacturers recommend multiple single element strings, i.e., 2 batteries in series in parallel with other groups of two batteries in series. This allows you to see how each individual battery is performing.

Parallel first is fine too, but you lose that visibility on individual batteries.

Ironman said:

Will one side of the parallel pack get charged up before the other.

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Depends on how it's connected.

Ironman said:

I can see the positive side getting the leftovers from the negative side.

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Maybe.

Ironman said:

He has a 60 amp mppt charger.

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A little undersized. A 760Ah bank should be charged at 76-152A typically.

Ironman said:

I hope I am wrong here.

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Again, depends on how it's connected. See Victron's "Wiring Unlimited" in Resources.

Thanks for your response Eggo.
I read the Wiring Unlimited and it was a good informative article other than from page 9 consistently getting the DC flow direction wrong. They have shown electron flow from positive to negative.
Electrons are repelled by the negative charge and attracted to the positive, so flow is from neg. to pos. terminals.

Hi,

I'm new here and i'm hoping to gain the best knowledge to enable me manage my solar system more efficiently.

I currently have a 5Kva 24v inverter with 8 12v 200a lead acid batteries. Its a Grid connected Energy Storage System and the battery bank is connected with in series of 2 12v battery and then connected in parallel as 4 sets of 24v.
My system is in its 4th year and 4 of my batteries just went bad. Probably due to bad connection setup, as i just discovered it would have been better to connect the main battery bank cable diagonally and with a bus-bar, rather than cables on one end. I also realized my solar system is too big for the battery bank.

Now i wish to replace my battery bank, but this time with a 16 12v 200a lead acid batteries. I would like to know the best way to connect it without running into problems. Should i connect them the same way as it was previously done as one single set of "2 12v battery in series to make up 24v and stack all 8 sets in parallel, or do i break it up into half by making it 4 parallel 24v setup on each; then combine them to my system?

I really would appreciate your professional advise, so i don't end up damaging my new batteries.

You would be better to post a diagram of your battery bank connections if you want advice, and read the above recommended files. There is a good way and a bad way to connect.

Hi,
Thanks for your response to my query. Attached below is the 8 battery system i currently have setup:




You may also find attached below my proposed 16 battery setup:

Neither are right.

The main lead should be connected to the opposite end of the bank.

Note that the end batteries will take on more than their fair share of load/charge. Current sharing will progress inwardly to a minimum at the center two pairs. This means the batteries will wear progressively faster as you progress from center to ends.

It is critical that you monitor the individual series 12V and confirm that they are nearly identical through the entire operating voltage range.

Picture 1 is pretty much the worst way to wire multiple banks. For best results, get a couple of bus bars and wire them as seen in Picture 2. Assume each black box is a 24v bank of batteries.

Rednecktek said:

Picture 1 is pretty much the worst way to wire multiple banks. For best results, get a couple of bus bars and wire them as seen in Picture 2. Assume each black box is a 24v bank of batteries.

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And if they are 12v each black box in the picture would be two 12's in series

sunshine_eggo said:

Neither are right.

The main lead should be connected to the opposite end of the bank.

Note that the end batteries will take on more than their fair share of load/charge. Current sharing will progress inwardly to a minimum at the center two pairs. This means the batteries will wear progressively faster as you progress from center to ends.

It is critical that you monitor the individual series 12V and confirm that they are nearly identical through the entire operating voltage range.

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Thanks for providing me with clarity on this topic. I will do this with bus bars.

Rednecktek said:

Picture 1 is pretty much the worst way to wire multiple banks. For best results, get a couple of bus bars and wire them as seen in Picture 2. Assume each black box is a 24v bank of batteries.

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Ironman said:

And if they are 12v each black box in the picture would be two 12's in series

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I don't think this is limited to AGM batteries, is it?
I have 4 Lifepo4 batteries and will use them as a 24 volt bank.
I would assume one would want all 4 of the long wires the same length. And in a perfect world the 2 short wires could be bus bars.
So, something like this?

You would be way better off to use lower voltage/higher ah. batteries in your bank. You have too many strings to manage even charging paths. You are showing 1600 amp hours total, at 24 vdc. You can buy 1,100 amp hour 2 volt cells. 12 of these would give you 1100 amp hours @24 volts in ONE string ! , super simple wiring and, being a single string, uneven charging is impossible.

littleharbor2 said:

You would be way better off to use lower voltage/higher ah. batteries in your bank. You have too many strings to manage even charging paths. You are showing 1600 amp hours total, at 24 vdc. You can buy 1,100 amp hour 2 volt cells. 12 of these would give you 1100 amp hours @24 volts in ONE string ! , super simple wiring and, being a single string, uneven charging is impossible.

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Is "You" the OP?

Actually, now that I review the thread my comment isn't for the OP. I was referring to RenExT, who I see now has a total of three comments and all are right here but as he jumped into this thread had me thinking he was the OP. My bad.

littleharbor2 said:

Actually, now that I review the thread my comment isn't for the OP. I was referring to RenExT, who I see now has a total of three comments and all are right here but as he jumped into this thread had me thinking he was the OP. My bad.

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Yep, I see it now as well. RenExT just popped in and out. Oh well.