Dual Battery Switch

[moorpark]

I'm planning to install a dual battery switch to better utilize both batteries in my bass boat. I'd bet the electrical systems in most boats float the negative side of the battery, but the outboard's metallic clamp to the transom might create a quasi-ground point for the electrical system. (The spark plug's negative side is the block and thus, the engine and it's mount)<br /><br />Even though I plan to common both negative posts of the batteries together and switch their positive sides via the switch, is there any concern about potential corrosive or electrolysis action on the hull of my aluminum boat? The sacrificial anode on the motor is in good shape, but will tying the grounds of both batteries together make the possibility of corrosion worse? (Fresh water application only)

 

[12Footer]

Re: Dual Battery Switch

Yes there is a corrosion problem created by using an aluminum hull for a common ground.<br />Allways (regardless of hull material type), use 2 conductors to all electrics and electronics. I have found the best stuff to use is that heavy duty speaker wire sold at auto sound and auto parts stores. It has a copper color and a silver color wire(silver negative,copper posative), and the insulation is thick,waterproof,uv resistant.<br />And it's cheap. But make sure it's the big stuff, you know, the kind they use in "boom-boom" cars.<br /> <br /><br />------------------<br />I'm no expert, but I DID sleep at a Holiday Inn last night!

 

[moorpark]

Re: Dual Battery Switch

Thanks for the response. Yes, I intended to use two separate conductors, but Radio Shack type wire isn't the size I'm planning to use. Instead, I'm going to employ #4 stranded with a PVC jacket. The current consumption of the trolling motor, combined with the length the cables need to be in order for them to be dressed, don't lend themselves to zip cord style, even if it does have an "attitude."<br /><br />I still don't understand how the aluminum boat manufacturers get around the electrolysis problem with an outboard whose electrical negative connection is via the motor's block. Is the sacrificial anode the solution?

 

[JB]

Re: Dual Battery Switch

Check your motor, Moorpark. I'd bet that the boat is not a return path, merely a floating ground. You should have two #6 or bigger wires for the starter. The negative serves as return for both the ignition and the starter. On some motors it is also the return for the alternator, on others there are two wires from the alternator/rectifier. This arrangement actually inhibits corrosion.<br /><br />Good luck.

<br />JB

 

[ODDD1]

Re: Dual Battery Switch

Moorpark, on non metallic hulls,we 'bond' all underwater metals [thru hulls,shafts,ect] together so all have the same potential underwater then a metal less "noble" like zinc is added to the system to sacrifice itself...end result..less corrosion on the stuff you want to keep... alum or steel hulls really no different.