24v 400ah Mighty Max battery bank

[TimmehTim]

Hi good people!!

I've made myself a 24v 400ah sla battery bank using four 12v 200ah Mighty Max SLA batteries.
Ive connected them in what I believe to be a series‐parallel as shown in the attached diagram.
My battery monitor is showing all sorts of numbers that I'm afraid I can't make sense of. At times, my external resistance will be 3 to 4 ohms. And on a few occasions it has shown internal resistance so high it just showed "- - -" as the reading.
I thought I'd start looking for answers to see if this is normal or if I have some things incorrectly wired or configured.
Is my battery pack rigged correctly?

 

[sunshine_eggo]

To be honest, that's so convoluted, I'm having trouble following it.

Why not this?




Parallel the 12V first and then series them with one cable.

 

[TimmehTim]

Because I've never seen a workup like that. Is that safe? I was going for what is shown on this diagram.

 

[TimmehTim]

To be honest, that's so convoluted, I'm having trouble following it.

Why not this?

View attachment 95232


Parallel the 12V first and then series them with one cable.

I had never heard of connecting all the terminals together quite like that. But in researching it a but more I've come across this other diagram showing all the connections right down the center, essentially showing exactly what you have. I can't find any info on the pros or Cons if either. Is there a name for this type of series‐parallel? Opening my mind a little, I can see where this might help the batteries balance better.

 

[sunshine_eggo]

I had never heard of connecting all the terminals together quite like that. But in researching it a but more I've come across this other diagram showing all the connections right down the center, essentially showing exactly what you have. I can't find any info on the pros or Cons if either. Is there a name for this type of series‐parallel? Opening my mind a little, I can see where this might help the batteries balance better.

That's a little different than what I have. I showed only a single series connection between the 12V groups to insure that the current flow is well distributed between batteries.

In the diagram you linked, the top two batteries would share the bulk of the load/charges and would likely wear out faster than the others. Either the positive or the negative needs to be connected to the 3rd battery instead.