Fuses at both ends charging cables?

Ken O

Ken O

Member
I'm upgrading my solar power and adding a DC-DC chargers. The chargers can't fit in the starboard lazarette/battery compartment, so they will go in the cabinet under the stove. This means that I will have 2 hefty cables with batteries at one end and chargers at the other. Current source could be at either end. Would there be any harm in putting fuses at both ends of a cable? We are usually told to put the fuse near the battery, but in this case, I could have 20 amps going the other way, and I don't think a short in the middle would care if there was a fuse at the battery end. Thoughts? Thanks.
 
I just went through this with the same sized DC-DC; I also put it in the galley cabinet. It sounds like you are building almost the same system I put together; I had a similar question :)

The manual for my DC-DC charger specified that ANL fuses were required at each end. I used one ATO at the start battery (Bluesea battery terminal fuse block type) and one ANL and it has been working great. My charger recommended 30 amp fuses at each end, which is acceptable for most ATO type fuse blocks.

You mentioned heavy wire. Double check the wire size you need for a 20 amp charger; the manual for my DC-DC charger, and confirmed by Bluesea's chart put me at 10 gauge, which is a lot easier to work with.

http://assets.bluesea.com/files/resourc ... hartlg.jpg
 
I don't think a short in the middle would care if there was a fuse at the battery end.
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Exactly! A fuse protects the wire downstream of the fuse. A short before the fuse (i.e., between the source and the fuse) could fry the wire (fire?) between the source and the short since the over current would not need to flow thru the fuse.

I think you're smart to put fuses at both ends to keep wire between source (any source) and the fuse as short as possible.

P.S. WCF is correct. Wire size mostly depends on max amps flow. Those huge cables you see on batteries are for the circuits that will carry 50, 100, or even more amps (volts don't matter except in terms of voltage drop for longer runs).....such things as engine start cables or inverters or battery to major distribution buss.
 
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