Charging 4 batteries with 3 bank charger safely

I am upgrading the electronics and power on an old boat I purchased recently. I replaced the batteries with new ones (2x 12v deep cycle batteries in series for trolling motor and a 12v cranking battery) and upgraded the charger from an old battery tender 10x2 to a new Bass Pro XPS 15x3. The previous owner of the boat had all house/accessory electronics as well as an old fish finder hooked up to the cranking battery, but the graphs/livescope I plan on installing will draw much more amps than I'm willing to put on the new cranking battery. I'm considering installing a 4th battery dedicated to electronics, but my charger only supports 3 banks.

Before I go too far with the idea of upgrading the charger, is there any way I could safely charge 4 batteries with a 3 bank charger?

Absolutely, positively.

Two of the charger leads each connected to just one battery. The third charger lead to the other two batteries connected in parallel. Via a manual switch or an automatic device (VSR/ACR/Combiner/etc).

You can run all your accessories just fine off of a Group 31 cranking battery, no need to add another one.

Kinda the same scenario i just did. I was told yes this can be done. Wire the cranking batteries together in parallel Lets call them A and B. Then take your charging lead and put the Pos lead to+ on battery A then the Neg lead to - on battery B

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Originally Posted by champ210

Kinda the same scenario i just did. I was told yes this can be done. Wire the cranking batteries together in parallel Lets call them A and B. Then take your charging lead and put the Pos lead to+ on battery A then the Neg lead to - on battery B

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This is the correct way to do it. Just be sure your jumper wires are big enough to handle the amperage and use fine stranded wire. Cj

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Originally Posted by CJ1

This is the correct way to do it. Just be sure your jumper wires are big enough to handle the amperage and use fine stranded wire. Cj

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Can you do this same process if one of the batteries is a LiFePO4 battery for electronics only?

There is a 2 page thread going on right now for Lithium and AGM in parallel