It does not end here as there are others out here.
Have been thinking about this (and watching an episode of Bull Tv series).
Claims on wireing and what the incorrect wire can do can be right but i would not be making statements unless i could see and do testing myself.
The comany a worked for ran a 12 volt 4400 Ah backup supply that would supply 500 amps continuous from a 3 phase power supply and 2 banks of 2 volt 2200 Ah cells and yes they were big!
Each cell measured half a meter square and stood almost a meter tall, there were of course 12 of them and they were wired series parallel with the connections to the controller off one end as per instructions from the company.
It worked! The wires were almost 20mm of copper.
We all know that there are optimal ways of wireing but physical space does not always comply with the theory of optimal.
Enough of that.
In reguards to your question, i am currently working on a system to go in my car (much less nerve racking than the thought of shorting a system capable of delivering 1000 amps ar 13.8 volts for 30 minutes).
It will be set up to run my car fridge and other electronics off the main car battery and a jumpstart pack which it will switch the load to before the main battery gets to low.
Any how i have looked at how to monitor the voltage on both batteries as well as amperage in and out of both.
I wanted to use the Arduino to control and store data but how? when the batteries operate between 0 and 16 volts.
I want to display voltage to two decimal points but the 1024 steps of the a to d dont give that resolution.
Then i realised that anything below 10 volts is useless to me!
Yay the good old Zenar! Working on a voltage swing of 10 to 18 volts and using an 8.2 volt zenar inline to drop my voltage followed by a voltage divider of 2K7 and 2K2 ohms gave me a voltage swing of 0.8 to 4.4 volts, purfect for the Arduino 5 volt input.
So by using the above and setting up another to handle 24 volts you can now monitor the two banks and set off an alarm if an inbalance occurs.
And yes i know the above COULD have ways of going wrong (lets face it Adruinos are cheap) but i did say i was working on it and it does not involve op amps masive voltage dividers or optocouplers.
Using a cheap boost/buck converter from ebay to run the Arduino off the battery bank is not hard.
Once in place you can start looking at more data and narrow down the faulty units, it will at least cut the problem in half.
Please dont set up a system that discharges the higher bank that seems wasteful.
Look at the way they do lithium cells in a pack this could be used for your system as well.
Still if you have cells that are not at full capacity (a speculation not a fact at this time) then the string will only run at the lowest capacity.
Could you tell me what is the largest current draw and how long it would go for?
Hope this gives more to think on and wait for more questions.