What battery to use with fishfinder

[getlinewet]

Guys:

I'm thinking about finally breaking down and buying a quality fishfinder. I'm also thinking of self installing it. My question is: should I connect the fish finder to the cranking battery or should I buy an auxiliary battery dedicated just to the fishfinder.

Thanks in advance for any help.

[striperjohn]

If you are getting total df pkg i.e. with Ds,Ss, sonar get a separate battery. The new DFs don't use much power but during a long day it adds up and a separate battery will prevent you from wearing down your starting battery. Plus most starting batteries are not meant for slow discharge. In the long run you will be glad you have a separate battery.

[getlinewet]

Thanks Striperjohn

[ghostcomanche©®]

I never had anything connected to my cranking battery but the big motor. All other electronics ran off my T/M batteries.

[tblspoon]

I'm just the opposite, everything (navigation lights, black lights, two fish finders, one live well pump, aerator and bilge pump) on cranking battery, only the trolling motor on the deep cycle battery.

Reasons are:
Trolling motor will cause interference with the fish finders, trolling motor wears on battery and your nav lights and pumps may weaken or stop.
Cranking battery will recharge when big motor is in use.
Always make sure that everything is fused with the proper amperage.

Just my opinion...

[striperjohn]

If you run everything off one battery, just Mho but that's asking for a breakdown of the main starting battery. I don't know about you guys but I'd much rather run out of TM or anything else before the big motor starting battery. Just saying. That TM interference is minimal if you use choke coils, most electronic stores have them for about 6 bucks each. A lot of this depends on how many batteries you have, what are they used for now? If you have enough reserve capacity then run the DF off something other than your starting battery. Also, need to know what type of charging system you have on your boat, any alternate charging leads (Yamaha has for example). Many configurations available. Tblspoon not sure if you live bait fish for stripers or what, but if you're dragging bait around for hours on end, running DFs and aerator pumps etc etc off the battery that starts your big motor, that will eventually lead to a problem. Been there and got the Tshirt! Now if you're greenfishing, where you're constantly running and recharging your battery, that's an entirely different situation.

[smlfishing]

I have the same set up as tblspoon but always had the same fear of my cranking battery (which I replaced with the biggest dual purpose optima battery) fully discharging that I bought a jump box just to keep on the boat. If you use your TM batteries  that are set up 24v can you tap into just one for 12V accessories and if you can will it not cause the two 24v batteries to be out of balance? 

[BentRod]

I have my fishfinders, all of my console electronics/lights, and my bait tank on a 29 group battery and my cranking battery does nothing but start the motor. A 29 is enough juice to run everything all day - a 27 would struggle after it was a year old - keep in mind I'm running two 8" fish finders and the bait tank - a 27 worked fine when I just had the one finder. I like knowing when I go to crank the motor it's going to start (well most of the time!).

[ghostcomanche©®]

Aug 22, 2016 8:37:15 GMT -5 smlfishing said:

If you use your TM batteries  that are set up 24v can you tap into just one for 12V accessories and if you can will it not cause the two 24v batteries to be out of balance? 

Yes, you can tap into one battery, and don't worry about the batteries getting "out of balance".  The amp draw from your electronics is low enough so it won't really discharge the one battery that much.  Once you charge the TM batteries, they will both equalize anyway.

I have run this set-up for over 40 years and have never had a problem.  If your using good batteries to begin with, you should be in good shape.

I also like not having to worry about my motor starting with the cranking battery. It's a real pain, at 3:00 in the morning, 10 miles from the ramp, to have a motor that won't start.

[smlfishing]

Thanks ghost, that would be a lot easier than adding an extra battery. I was always just unsure if that was strictly 24v once you tied them together.