Electronic Interference

[chucker]

I recently set up an older sitex flasher (fl-7) on the bow of my boat. When I use the flasher in conjunction with the bow trolling motor (24v autopilot) I get interference on the flasher?

I wired the flasher to one of the deep cycle batteries used in the 24v system and the
flasher transducer is mounted to the trolling motor.

Is there anything I can install in the power line of the flasher to eliminate this interference, or do I need to wire to the starting battery?

Any help would be really appreciated!

[Wave Runner]

Wire to starting battery, problem solved. Never wire a depth-finder to a battery that has a trolling motor wired to it.

[Guest]

You can install a common ground off the battery but with more than one battery it may not work depending on whats used for the boats main base ground. The best way to solve this common problem is to wire the flasher to its own battery...

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[chucker]

Wired locator to starting battery, problem solved. I am very concerned about draining the starting battery (not much fun starting a 90 merc with a pull rope).

With the livewells, nav lights, interior lights and all other accesories wired to the starting battery I think it draining the starting battery is a real possiblility.

I sure seems like there should be a way to condition the power from the deep cycles to eliminate this interference?

I either need to install a third deep cycle for accesories or rewire non-sensitive items to the deep cycle circuit.

[Gill]

Chucker,
I observed the same problem last year when I hooked up an FL-8 to a deep cycle along with a new Minn-Kota PD. In the past, I had an old all-terrain trolling motor and never experienced any interference. Someone correct me if I’m wrong, but the interference you get from the trolling motor is due to the solid-state technology used to increase efficiency in the newer trolling motors. To adjust motor speed, Minn-Kota’s Maximizer utilizes pulse-width modulation, switching the motor ON and OFF at about 20-kHz. This fluctuation in current draw off the battery is bound to screw up any frequency-sensitive accessories. So, I guess you could place a low-pass filter before the depth finder, if you are set on connecting to the deep cycle. However, use a filter that has a cut-off frequency well below 20-kHz (true DC current has a frequency of 0-Hz). Radio-Shaft has all the components you need to build your own.

[Surface Tension]

Nothing should be on your starting battery other then the depth finder. There is no way your going to drain your battery with a depth finder! You could leave it on for a week and still start your motor. Put the lights, livewell and accessories on the deep cycle.

[chucker]

Thanks everyone for the input. Looks like a rewire job, shouldn't be to tough.

Think I will run my fuse block to one of the deep cycles and run the locators to the starting battery with inline fuses.

Unless theres a better way to do it?

[bigeyes]

Yes, I agree, it should go to the starting battery. You prabably can leave it on for a week and still fire the motor(knowing me I am sure I will someday), but I can vouch for leaving it on for a couple of days, though. Even made it over night with the backlight on, which does pull much more amps. Just make sure you don't skip the inline fuse!