Solar array with small batteries

ddesigns

I am looking into a solar array for my R/V.  BUT I want to be able to take one of the batteries out of the array to use for my trolling motor on my boat.  I currently have a small 30aH AGM that does the job for a day on the water, but only a day.  After that, it needs recharging. So if I go on a four day trip, and carry 4 30aH batteries, I was hoping I would be able to round-robin them out and use one a day on the water.  But, I now see that introduces a battery back in to the bank that is much more discharged than the remaining three.  I was thinking I could put some kind of charge regulator (if there is such a thing) that would take the charge current and distribute it across the batteries where it is needed most.  E.g. if the bank of four has one that is discharged further, then the full charge current would go to that battery, and the other batteries would be cut out of the charging loop by the charge monitor.  It would seem this would be possible, since they make battery chargers that can cut-off when the battery is fully charged.  But I do not know, as I am a newbie.  So any help would be appreciated.  Initially I had though I could buy a couple of 100aH house batteries, and two 30aH trolling batteries.  But in my research everyone says the battery bank should be all the same batteries both in technology (AGM/LiIon) and aH, and as well by the same manufacturer and of the same age.

Ideas?  A 100aH battery is way too big for my little boat, but I feel like a bunch of 30aH batteries is overkill and wasted space and money, compared to a couple of 100aH.

I thought perhaps I could use a marine switch to isolate the one battery when I return to shore, and just let it have the entire array until it registers fully charged, but then that doesn't help me when I switch back to the full array and now I have varying battery capacities.  So I am at a loss......

mike95490

Morningstar’s SunSaver Duo is for charging 2 different battery banks.  But I doubt it can use power from one bank, to charge the other.

And you do not want to connect a low battery, to a charged bank, you will get a huge amount of amps and that can cause a steam explosion of the low battery as hundreds of amps rush into it.

You may want to devise a way to switch part of your array to power a 2nd controller for the trolling battery

https://www.morningstarcorp.com/products/sunsaver-duo/

And finally, if it was me. I'd use the same batteries (100A) in all places, and designate one for trolling.  That one will age faster than the others and wear out sooner.   Do you only use the trolling motor, or do you have a gas motor to get you to the fishing spot - maybe the gas motor has a battery charging circuit you can use to assist charging the battery on the way back, and it won't be so empty