Adding deep cycle for stereo

[MILD THUNDER]

My boat currently has two alternators, two batteries, and one switch. I plan to ditch the old style low amp alternators, and go with some 1 wire 100 amp guys.

I'd like to add a third battery, just to run the stereo while on the hook. Im guessing a deep cycle with an isolater?

[flamingo 32]

last season I upgraded my system adding two power amps, I added a third battery and changed my isolator to a two alternater,three battery one, worked really well

[Scarab KV]

My boat currently has two alternators, two batteries, and one switch. I plan to ditch the old style low amp alternators, and go with some 1 wire 100 amp guys.

I'd like to add a third battery, just to run the stereo while on the hook. Im guessing a deep cycle with an isolater?

That's how I'm set up. I run the same deep cycles that we use in the Petes and reefer units.

[Griff]

I would add a second battery switch. The issue I see is that you are putting a lot of charging amps to one battery, and with upgraded alternators, it will be even worse. Deep cylces like a slow charge. I guess you could run the switch on "ALL" and use an isolator. I just like to have a little more control.
I have 2 regular marine batteries and one big deep cycle for the stereo. I have 2 perko switches. #1 on each switch is for the battery for each engine. #2 on each switch goes to the deep cycle. I try to never run both switches on #2 or "ALL" at the same time with both engines running. With the way its wired, I can start both engines as long as I have one good battery. I can also use 2 of the batteries at a time to run the stereo for a long time if I want.

[Airpacker]

Griff, you are only EVER "putting alot of charging amps to one battery" IF that particular battery is low on charge. As battery voiltage rises, the regulator reduces amp out put from the alternator accordingly. It doesn't matter how big the alternator is unless you exceed the needed out put rating of the alternator.

Now, I do like the way you wired yours. The problem with using one switch and an isolater on one motor is that the deep cycle battery will get run down at the beach. The starting battery will not. Once you start cruising again, the starting battery will get an excessive charge rate and boil because the reference voltage the regulater is using will be low due to the drained deep cycle battery.

Better off using two switches.

[old377guy]

great info as I am going with the third stereo battery project this Winter