View Full Version : Fish Finder on Separate Battery?

10-23-2005, 03:33 PM
I seem to be getting quite a bit of surface interference on my fish finder and wondered if it was because I have it and my electric trolling motor connected to the same battery. *I also have the transducer mounted to the trolling motor with the Lowrance trolling motor mount.**

I was contemplating using a separate battery for my fish finder to clear up this problem.

10-23-2005, 04:31 PM
i think amotorcycle battery would be a good experiment. let us know how it works.

10-23-2005, 06:00 PM
Surface noise is normal. *If you have to much you may need to adjust the sensitivity down a bit. *To tell if it interference from the trolling motor view the FF with it running and not running. *If it is the same both ways then its not the motor. *If there is visibly more noise with the troliing motor running seperate the wires (FF wires vs trolling motor wires) as much as possible.

I used to run my fish finder on the smaller terminals and the trolling motor of the larger terminals.

The problem with the motor cycle battery is that they are made to discharge and recharge as often as a deep cycle battery. Of course the FF wont drain it very often either.

10-23-2005, 06:49 PM
I have the Lowrance FF unit, also mounted to my Minkota Power Drive with a hose clamp.
I use a second bat to avoid noise and clutter. However, I still get very minimal clutter when the trolling motor is on.you can tell when you switch on and off.

10-23-2005, 07:10 PM
If you use smaller gauge wire than recommended you can get interference. Also, if you co-mingle your wires you can get interference. Keep your fishfinder wiring away from your motor wiring and bilge pump or any large draw as much as you can.

The ground wire is generally the more important wire to protect.

If you do need a battery, Cabela's sells a small deep cycle battery and charger for around 25 bucks that should do the job. I use one on my kayak for a 150 dollar fish finder and it lasts for a week or more. In fact it is too big and I have a hard time drawing it down.

10-23-2005, 08:18 PM
Reno I had a separate battery up on my last boat. I had the same problem you had. The separate battery worked fine. I bought a Totally sealed battery that was very small in size from Batteries plus. I want to say it was a 12 amp. They had 7, 12 and 18 amp batteries. It was like 30 bucks or so. No water Totally sealed deep cycle. Made a little box and mounted it under the dash. Cabelas has them in one size. 7 amp I believe. If you have not checked out batteries plus It is worth a look.
Good Luck

10-24-2005, 06:29 PM
Thanks everyone for all the advice. I'll separate my wires and run my fishfinder on its own small battery.

10-24-2005, 08:55 PM
Like someone already said surface noise is normal. It can be reduced by decreasing the sensitiviy of your fishfinder. Lots of times I'm trolling for fish that are more than 10 ft below the surface. In that case I'll set the depthfinder upper depth of the finder at 10 or 20 ft. When I do this, any surface noise isn't displayed at all. The kind of noise I've experienced when an electric trolling motor is causing interference with a depthfinder doesn't look like surface noise. It's usually looked like faint vertical lines running from the top to the bottom of the fishfinder display. These lines appeared everytime the electic motor was turned on.. Larry

10-25-2005, 09:05 AM
Reno I run mine on a seperate battery, its a 26 amp hour and will run the unit for 2.5 days without a charge,, I'm going to a bigger battery though cause sometimes I fish for 3days and I'll lose my GPS when the voltage drops to low.

50 amp hours would be the ticket.

10-25-2005, 04:09 PM

Thanks for doing the field testing in order to make the recommendation on the 50 Amp hour battery. I'll see if I can find one that's not too heavy.

10-25-2005, 08:30 PM
Sometimes coiling the hot lead to the fish finder will help reduce interference and clutter.

10-25-2005, 10:33 PM
Speaking of coiling the red lead reminds me of a solution I read about. It was to coil the red lead fishfinder power lead around a ferrite core that was sold at Radio Shack. This created a choke(inductor) that choked out the high frequency signals from the trolling motor. A trolling motor will emit a high frequency signal every time it is pulsed on. This hi frequency signal sometimes causes interference on a fishfinder. It worked and was written up as a trick solution in Bass and Walleye Boat Magazine.. Larry