Questions I get in my inbox (fuses for fishfinder)

[Fiskadoro]

I get a lot of tech questions in my inbox, this one I thought I'd share....

I have a question. I just bought a second 12v 7A battery to separate my bait tank and fish finder...... Anyways, my question, is it necessary to have an in line fuse if I have my fish finder hooked up directly to it's own battery? Just wondering what would happen if I didn't have one. ruin my FF? Thnaks for the info.

It would not hurt the fishfinder unless a short formed in the fish finder itself. For instance say you decked a big halibut and it smacked the shit out of the finder while flopping. In theory if something came loose and actually shorted across from pos to neg in the finder, that would make a direct short which could cause the finder to physically burn up and or even melt down your battery. Worse case scenario the battery over heats to the point it melts a hole in the battery case and then through your hull of your yak making a massive hole and sinking it... Not good..... or more likely the wires themselves heat up to the point the melt into your hull, equally not good.

So to avoid these potential disaster scenarios I always wire in sealed inline fuse holders to the finder. Here's one in my X-13..


The holders I use are Bakelite, I think made by Tron. They have built in crimps at both ends, an internal rubber seal, 100% waterproof and from what I can tell virtually maintenance free. I've not had to crack one yet.

The truth is you can do it without a fuse and it will work but you better make your setup so you can get to the wires fast and disconnect them from the battery, because if you do get a short somethings going to get hot fast.

I have to use a fuse because I use a NIMH battery that is 10AH for my fish finder. it's about half the size and weight of your 7ah lead acid.
Those batteries are capable of discharging so much power so quickly you can practically weld with them, and they can cause real problems if they short. Since they are about a 100 bucks a pop I don't want to kill that battery.

One additional comment I'd make is that I'd run a separate battery and separate voltage for your finder and pump. I run my pump on a 6V 10ah Lead acid battery for my bait tank. It's got a better slower flow rate and it lasts much much longer. I also have the wires set up so I can switch it to the 12v if necessary.

Basically I do that so if I have a problem with one battery I can switch to the other. Thought it's only fused when on 12 volt. Then again the wires are right there where I can get to them, only about a foot to the pump and are not touching the hull.

Set up this way I can run both the fish finder and tank for more then 12 hours at a stretch which works for me.

So Yes I'd recommend a fuse, but I'd also switch to a second battery for your pump or your going to find yourself running out of juice all the time. That is just my take though..

Now you got me thinking I should just fuse my pump as well. Couldn't hurt and might save me some real problems down the line.

Jim