Thread: Fuses for Fishfinder wiring.

how far can that switch be from the batteries and the fuse panel? What gauge wire would I need for say 3-5 feet?

It is best to have the disconnect switch as close to the battery as possible to protect the entire wire circuit if the battery shorts out ...

Remember ... the most likely place for a short is at the battery or the battery itself - breakers, switches and fuses will only protect things “downstream” of the protective device installed ... (thus the need for the first protective device as close to the battery as possible) ...

I’ve seen many boats wiring from the battery to a fuse panel with thinking only of protecting electronics devices - with no thought of protecting the wire between the battery and the fuse panel ... (wire fire hazard if the battery shorts) ...

If it is not feasible to install the disconnect switch within a short distance (I think ABYC standard is like 7” between the battery and the first protective device) - then it is possible to add a circuit breaker at the battery post ... this protects the wire from melting if the battery shorts (regardless of “if” there is a disconnect switch installed or where the disconnect switch is installed in the wire circuit) ...

It is good practice to have a circuit breaker at the battery post with heavy wire thru the disconnect switch and on to the Buss bar fuse panel. ... Then use correct fuse sizes and wire sizes for the individual electronics device(s) runs ...

This practice protects everything “downstream” of the battery post ...

Here is info for marine wire size per length of run ...
Marine Wire Size and Ampacity | West Marine

Rickie

Originally Posted by rnvinc

It is best to have the disconnect switch as close to the battery as possible to protect the entire wire circuit if the battery shorts out ...

Remember ... the most likely place for a short is at the battery or the battery itself - breakers, switches and fuses will only protect things “downstream� of the protective device installed ... (thus the need for the first protective device as close to the battery as possible) ...

I’ve seen many boats wiring from the battery to a fuse panel with thinking only of protecting electronics devices - with no thought of protecting the wire between the battery and the fuse panel ... (wire fire hazard if the battery shorts) ...

If it is not feasible to install the disconnect switch within a short distance (I think ABYC standard is like 7� between the battery and the first protective device) - then it is possible to add a circuit breaker at the battery post ... this protects the wire from melting if the battery shorts (regardless of “if� there is a disconnect switch installed or where the disconnect switch is installed in the wire circuit) ...

It is good practice to have a circuit breaker at the battery post with heavy wire thru the disconnect switch and on to the Buss bar fuse panel. ... Then use correct fuse sizes and wire sizes for the individual electronics device(s) runs ...

This practice protects everything “downstream� of the battery post ...

Here is info for marine wire size per length of run ...
Marine Wire Size and Ampacity | West Marine

Rickie

I appreciate the response but I don’t understand. I don’t know what it meant by protective device. I guess this is just too complicated for me. What is the ABYC equals 7A in your response. Is that 7 feet


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A protective device is a circuit breaker, a disconnect switch or fuse ... a device that protects the wire circuit running to the electronics stuff ...

The ABYC (American Boating and Yachting Council) standard is less than 7 inches between the battery and the first protective device (there can be more than one protective device in a circuit) ... and that still leaves 7 inches of wire unprotected if the battery shorts out (which is why I recommend a circuit breaker at the battery post to not leave any part of the wire circuit unprotected) ...

Rickie

Not sure what you mean by "the battery shorting out". If this happened internally to the battery there would be no current in the wire, and no device would protect anything. The protection is for the much more likely scenario when a short (positive wire touching negative wire) occurs downstream of the battery due to a pinch, cut, or collision with something that damages the insulating plastic. The wires then conduct way too much current and get smoking hot, causing an electrical fire. This is why the main or first breaker needs to be close to the battery, and sized appropriately for the wire gauge.