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I looked into batteries extensively a few months ago when researching Solar and wind power. It is a great idea to have a separate thread for each of the battery types. In this case , flooded wet cell / lead acid batteries.
I was thinking in my case, Solar / Wind battery storage that salvaging used batteries for the lead and make one large 4ft. x 4ft. x 2ft battery so I would only have one battery with no voltage loss caused by separate batteries trying to equalize the volt differences across the battery pack/ the multiple batteries.
I think one big lead acid battery may be the way to go in your case for the electric car it would eliminate the same problem caused by the voltage differences between the various batteries, as they age.

Or in the EV world do they have a charge control module that eliminates the batteries from charging each other?

My best idea may be to recycle the lead from dead batteries, for your battery builds,it would save a fair amount of $