Utilizing Boat's Ground for Hooking Up Downrigger

DreamMaker

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Jun 14, 2007
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Hello Everyone, I have a 14' aluminum boat with a 25hp Honda outboard. I have two batteries: The motor battery powers the motor, fishfinder, bilge pump, livewell, navigation lights, and a Cannon downrigger. The Auxilliary battery powers the Minkota Trolling Motor.

I would like to switch the Cannon downrigger to the Auxilliary battery so that it doesn't drain my motor battery, which by the way has already happened to me and caused me much grief - lesson learned. The problem is that for the Cannon Downrigger's "Short-Stop" and "Positive Ion Control" to work, it must be hooked up to the boat's ground which is the Zinc Electrodes by way of the motor and motor battery.

So now for my query: a) Would I be able to continue the boat's ground to the standalone Auxillary battery by hooking up a wire between the negative post of the Motor battery and the negative post of the Auxillary battery? Would this give me the same result? b) Would this arrangement cause any complications or be detrimental to the life and usage of the batteries?

Your thoughts and comments will be greatly appreciated. Thank you.
 

mfkadz

Petty Officer 2nd Class
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May 26, 2015
Messages
135
A cranking battery was not really designed to have all that stuff hung off it. Unless your running the motor all the time like a car.

Because of the constant use and current draw. I would move the fishfinder and livewell to the deep cycle battery running your trolling motor. Then you should be ok with your downriggers on the cranking battery. Or, get a dual purpose battery to replace your cranking cell. A size bigger than you would normally need. That would give you extra service. But I would still move at least the FF to the deep cycle.

I had a portable color Hummingbird FF. A small thing. It was powered with a 120 CCA (4-wheeler battery) and was good for about 7 hours. That was without anything else on it.

Mike
 

DreamMaker

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Jun 14, 2007
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mfkadz: Thanks for the reply, my cranking battery is an Odyssey Trolling Thunder/Dual Purpose AGM battery. The Cannon downrigger uses "Positive Ion Control" which continuosly puts out a small current. This is why I would like to hook it up to the Auxillary battery. I will take your idea into consideration and likely hook the fishfinder to the aux battery as well but would still like to switch over the downrigger. Just need to know if linking the two negative posts will work without harming the batteries.
 

mfkadz

Petty Officer 2nd Class
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May 26, 2015
Messages
135
Had to look up PIC.

Ground is ground. And if I apply my tube power supply thoughts. I generate 3 different voltages and they all use the same ground. So I'm thinking this should be ok. I might do a little looking online later for any other info on that.

mike
 

duped

Petty Officer 1st Class
Joined
Aug 26, 2009
Messages
307
Yes, that will be fine. You only run the risk of discharging the stronger battery with the weaker one if you have BOTH terminals wired to each other. (paralell).

Although your plan would suit the basic needs, I would strongly consider adding a Perko battery switch. It would give you the option to select which battery to pull from and also give you the option to combine both batteries to start the engine in an emergency.
 

DreamMaker

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Jun 14, 2007
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A big thank you to all that responded :)

I also got confirmation of the above from the Odyssey Battery and Cannon technical reps.
 
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