Thread: Fuses for Fishfinder wiring.

any time you connect to a battery you want a fuse (or breaker) as close to the connection as possible. An inline fuse holder works great. Your main fuse that supplies power to your fuse panel needs to be rated to support a little more than the sum of all the devices you will use. The helix 7 says use a 3 amp fuse, the actual draw of the 7 is probably 1.5-2 amps and will say in the specs for the device. You get the main fuse size by adding the actual draw.
Ultimately the fuses are only to protect the wire from becoming hot knives and catching fire when something shorts out.
If it was me I would get a blade style fuse panel on amazon and put a 25amp main fuse at the battery and a bunch of 10-15's in the panel for your devices. You can always use a little bigger fuse, but you cant go smaller. If your device itself fails having a perfectly rated fuse is extremely unlikely to save the device as a fuse pops because the device already failed. Dont let people scare you, this isnt rocket science but you alway always ALWAYs want to use fuses. Even a single fuse at the battery would be sufficient for safety, but if one device or wire fails all your devices would go out which is why you break them down with individual fuses.

Remember that the primary function of a fuse is to protect the wire itself - not the electrical devise.

You do not need a slo-blo fuse. I discarded the 3AG fuse holder on my Helix, and wired to my Blue Sea fuse panel using a 4A blade fuse. I am an EE and consider this to be perfectly fine, and it has been so far (months).

You must take the size and length of the wire in consideration.

FYI, wire length has nothing to do with fuse/breaker rating. Wire gauge size only. The length of the wire has to do with how much voltage is dropped due to the copper losses. I used 8 AWG tinned copper marine wire from the battery & breaker (40A) to the Blue Sea panel. Almost no voltage drop.

Originally Posted by jawjatek

FYI, wire length has nothing to do with fuse/breaker rating. Wire gauge size only. The length of the wire has to do with how much voltage is dropped due to the copper losses. I used 8 AWG tinned copper marine wire from the battery & breaker (40A) to the Blue Sea panel. Almost no voltage drop.

You are right. I was thinking voltage drop. That's what happens when you get old.

ok, going to try this today. i got a 6 circuit blade style fuse panel with negative terminal. I am going to mount within 1 foot of the battery. I am going to connect to battery with 8ga battery terminal wires. I am going to put a 40 amp blade style inline fuse on power side. I am going to connect 1 echomap 93sv, 1 helix 12, 1 helix 7 di gn2, 1 helix 7 combo si/di gen 3n and a panoptix livescope to the blade fuse. i have 3 amp fuses fir the helix 7 and 5 or 7.5 amp fuses in the fuse panel for the helix 12, echomap and livescope black box.
I am also considering adding a second battery in parallel to double capacity. if so i am going to connect them with 4ga battery cables

Originally Posted by crappiejim

I am also considering adding a second battery in parallel to double capacity. if so i am going to connect them with 4ga battery cables

If you are going to add a 2nd battery, then do yourself a favor and buy a Perko battery selector switch (with one, two, both, off). That way, you have only one hot feed into the terminal block plus you have the ability to isolate each battery separately or turn off all power drains from your battery.