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Author Topic:   Console wiring for sonar and other accessories
17 bodega posted 05-31-2006 07:31 PM ET (US)   Profile for 17 bodega   Send Email to 17 bodega  
I am re-wiring my console and have purchased a nifty little 6 switch panel with newer fuses and LED indicators.

1. Why should a sonar/depth finder be wired directly to the battery as opposed to a fused panel switch?
2. Should other accessories like a VHF be wired direct to a battery too?
3. What would be any advantages of wiring a marine electronic device (of any kind) directly to a battery?
4. What type of conduit or wire housing can be used to run wires along the floor of a boat to the console? Or would it be acceptable to run (let's say for a bow light) a wire all the way from the bow to the stern down to the bilge (rigging tunnel) back up to the console, to avoid having to traverse the deck of the boat and create a trip hazard. (don't tell me I answered my own question!)


Tight lines mates...

Electrical feng shuei here I come!

Chuck Tribolet posted 05-31-2006 09:08 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
The only thing that should be wired directly to the battery
is the bilge pump, and then only if it has a float switch
and a fuse.

But use an adequate gauge of wiring to connect your panel to
the battery.

No problem running wiring in the bilge tunnel. Just use
marine grade wiring (Ancor is the best known brand). That's
what Whaler did for my bow light.


17 bodega posted 05-31-2006 10:21 PM ET (US)     Profile for 17 bodega  Send Email to 17 bodega     
Thanks for that Chuck.

For some reason, the manufacturer (Lowrance) has recommended the straight wiring to the battery. I will check that again to make sure. I used 10 gauge wire for the connection from the battery to the panel (This is the thickness supplied by the panel manufacturer. The common ground wire that comes off the panel is very wimpy, but I used it figuring it was adequate since it was OEM.

I solved my bow light wire issue by running it all the way down the rubrail to the stern light connector. The only issue now is to tie the stern and bow light together. I may end up having to run a separate set of wires to make it simple, but am wondering about a possible 3 way switch or method to avert pulling more wire through.

Is there any problem with using some 3 way male adapters and tying into the stern light with the same switch? I thought about putting a small set of terminals at the stern like the old stock whalers had.

Any ideas or input welcomed and appreciated.


aquaman posted 05-31-2006 11:05 PM ET (US)     Profile for aquaman  Send Email to aquaman     
Things like sonar should be wired direct to battery to avoid interference from other electrical circuts. It is also recommended that an amplifier or stereo be wired directly for the same reason. I agree that on some boats the bilge should be direct wired.


Chuck Tribolet posted 06-01-2006 09:54 AM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
I think I'd upgrade the ground wire too.

Your batteries are in the stern?

You have two lights, bow light, and all-round stern light,
right? If so then you have to wire it so that you can turn on
both (while running) or just the stern light (at anchor).
That requires a DPDT center off switch. You may be able to
replace one of the switches in the panel. Whose panel,
what model? and we can probably point you at source for the
switches. And you'll need to run the bow light wire through
the console.

Next time you pull a wire through the console, leave a string
(1/8 nylon parachute cord is good) behind for the next time.


17 bodega posted 06-01-2006 10:52 AM ET (US)     Profile for 17 bodega  Send Email to 17 bodega     
Yes, I have the bow light, and a long 360 degree stern/anchor light. With the "center off" switch both hot wires and a common ground are wired to the switch? That makes sense.. but it might just be easier to wire the two lights separatley.

The panel is a "victory" model #AA10064LTW 6 gang lighted white. The switches are all the rubber coated toggle style. I already picked up the wire and I'll pull it through today.

I have two batteries in the console, and I also just purchased a perko two battery switch with alternator "field disconnect". that will be my next project.

Thanks for all the help.


ratherwhalering posted 06-01-2006 07:41 PM ET (US)     Profile for ratherwhalering  Send Email to ratherwhalering     
I was under the assumption that only the negative grounds need be isolated to prevent any interference from parallel electronics. Is this incorrect?
JMARTIN posted 06-01-2006 08:08 PM ET (US)     Profile for JMARTIN  Send Email to JMARTIN     
Steve, my Lowrance said the same thing, wired direct to battery unless used in salt water, then they wanted a switch. I put mine on a switch and it has performed very well. John
Chuck Tribolet posted 06-01-2006 08:20 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
Use a DPDT center off switch. Wire power to
both middle terminals. Wire the bow
lights to one terminal on one side. Wire the
stern light to both terminals on the other
side. If the switch has a pilot light, wire
that like the the stern light.

No need to switch the ground.


jimh posted 06-01-2006 11:41 PM ET (US)     Profile for jimh  Send Email to jimh     
When instructions call for a device to be wired directly to the battery in order to reduce potential of interference (pun intended), the manufacturer probably is worried about introducing common mode power supply noise or voltage variations into the supply to his device. It would be far more appropriate if the device contained proper power supply decoupling so that it was not necessary to wire directly to the battery.

The notion that you should or could wire all devices directly to the battery is a flawed concept. There is a general rule in electrical practice that demands that only one conductor be secured under each screw terminal. Thus, in a proper installation, there ought to only be one wire or cable connector to the terminal on a battery. This wire or cable should in turn be connected to a distribution block, with proper fusing. Devices should be wired to the distribution block, and not to the battery terminal.

The concern about common mode interference is along this line. Assume there are two devices, A and B, connected to the power source and drawing their current from a common distribution line. The distribution wiring has a finite resistance R of 0.1-ohm. Let us assume that device A draws a current I of 20-amperes. This causes a voltage drop in the distribution of (20 x R) = 2-volts. Because device B is connected to a common distribution, it also sees a voltage drop of 2-volts. Thus device A can modulate the voltage to device B. If device B is sensitive to variations in its supply voltage, this fluctuation can cause interference in device B.

Also, if device A has very poor power line decoupling, it may put some noise or hash on the power line itself. This will be coupled into device B by the common power line. If each device had a separate power line, the noise would tend to be shunted away by the very low impedance of the storage battery. In this example, if each had its own power distribution with resistance 0.1-ohm, the common mode path would be via a 0.2-ohm circuit with a shunt to ground of the battery, which represents an extremely low impedance, probably on the order of 0.01 ohm. The ratio of the two (0.2/.01) would be about 1:20, and this would tend attenuate any common mode noise between the devices.

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