I am tinking of adding a second battery

[fishdawg]

I currently run a 16' Crestliner, it has a 2004 30hp 4stroke Johnson. I do a lot of trolling with it and run all of the accessories of my 27series crank battery (electric downriggers, sonar/gps, Sub Troll, VHF radio, ect..) These are all hardwired indivually (with inline fuses).

The house (lights, bilge, livewell) and motor came indpendently wired together.

Ive been running like this for a few seasons now with no issues but am considering adding a second (smaller) 12v battery for the trolling accessories. Is it neccessary?

If I choose to add a second battery, what would be the best way to go about doing it so that the alternator would charge both?

[ray koziatek]

I tinkI tout about that once!

[Big Dave]

You run a batt switch and a batt isolator. That keeps the main batt and the aux batt. charged and keeps the aux batt from being discharged. Switch from batt 1 to batt 2 when batt 1 won't start the boat. Boat us had a wiring diagram.

[Has Been]

On my boat of similar size I have 2 large Walmart best Deepcycle /starting batteries. I have one for just my motor & one for everthing else. This way I figure I will never kill the motor batt & get stuck out there. If your motor has a alt, get a dual batt switch & wire to intructions. I am going to get a dual bank onboard charger/maintainer for when out of water this year.

[fishdawg]

thanks fellas!

[Knotlost]

There is a switch that is out now that comes with exactly what your looking for. Its called "add a battery" it has a charging sensor to monitor your start battery and charges it first and when thats all fat and happy shunts the charging power over to your house battery. Run all your "stuff" off buss bars off your house battery, don't use your switch its not made for that. Run your buss bars after the switch, this will make your wiring very clean and organized.