For those who pull crankbaits and/or jigs with a 24 volt trolling motor using 4 batteries, do you parallel them all together or keep as separate pairs with some type of switch. If you are using a switch, what type?

I currentlly have two 31's batteries on boat but have another set lying around shop. Thinking about putting in boat. I have had long days where a fresh set of batteries would have come in handy. Also have another 2 bank charger I can utilize in addition to the 3 bank on the boat. Which will make charging 4 batteries no problem.

Appreciate any feedback or comments.