Battery Combiner/Isolator and 3 Bank Charger

[-Marc V-]

I know there's another thread on multi-bank on-board chargers but adding a new wrinkle to it.

Just got a different boat that has a 24v trolling motor and a starting battery with a 3 bank charger. The previous owner was running everything in the boat, except for the trolling motor, off the starting battery. I was thinking of getting an additional battery just for the accessories and leaving the starting battery for its sole purpose of starting the boat. Then linking the accessory battery and starting battery with a battery combiner so when the starting battery is full it feeds the accesory battery.

My question is would I be able to hook up the on-board battery charger to the battery combiner and when the starting battery is full when the charger is plugged into it the combiner will change over to filling the accesory battery?

I was thinking of getting a battery combiner anyway so the alternator can fill one or the other accessory or starting batteries, but wondered if this would also work from the on-board charger without spending the additional coin on a 4 bank charger.

Thanks much!

Marc

[marine_man]

Without knowing the specifics of the isolator you're considering, it's tough to answer for sure; however, I would expect that with the leads on the starting battery from the charger that when the starting battery hit the cutover voltage level you would be able to charge both.

The risk is that if both batteries are drawn down, it will take longer than a dedicated bank on the charger. However, with the alternator on the main motor feeding the starting battery this shouldn't be a frequent issue.

marine_man

[-Marc V-]

That's what I was thinking too that the alternator would keep the starting battery pretty full for the most part so when charging on the bank charger it wouldn't take long for the starting battery to top off and for the combiner to change over to the accesory battery.

Any suggestions on a combiner? I didn't really dig into them too much yet to get my head wrapped around them. Was kind of maybe a little wishful thinking that it'd even work in the first place. Would kind of like a combiner that would be good for gel/agm batteries too, if it matters, if I decide to go that route in the future. Always planning ahead. 😜

Thanks much Marine Man!

[gunner55]

We have a older MK 2 bank/10amp/per(05 or 06 ?) charger that is wired so the TM batteries won't charge unless the starting is fully charged.We run a 12v PD TM on the bow plus have a 24v on the transom.The 24v doesn't get used that much.It's rare but the starting battery will get low once in a while,it takes a long day of using the 12v pretty hard.I will just watch the battery level on my electronics so when it starts getting low I just start the outboard & let it idle.Last year I added another jumper wire so I can hook the 2 TM batteries together to use as 12v