Fuse block

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Scout

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I was shopping for a fuse block on amazon and they have ones with and without ground. I'm sure the correct way to wire it is run a positive and negative from the batteries to the fuse block and run a positive and negative from the fuse block to each load. Also ive seen 1 fat wire from the fuse block to a negative bus bar and all load grounds to that bus bar. 
I'm guessing the fuse block with no ground is using a chassis ground. Does this all sound correct? Is there one way better than the other? If i could do it either way i would rather run all grounds back to the fuse block.
 

safarivan

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the ones with the ground are made boats and other fiberglass body stuff mostly. unless you have a specific need for a separated ground circuit, its not necessary however. I bought one with the ground anyway just in case I may find or run into a need for that. you can use them the same as the ones without.
 

highdesertranger

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you can go either way. however I would go with Blue Sea brand. highdesertranger
 

Weight

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It is easy to bring all the devices positive and negative wires to the fuse block. It is like having a negative bus bar. You could then bring the negative back to the battery, or if you are sure of the chassis connection, bring the negative there. I have two fuse blocks. The one for the water pumps and a few lights is returned by the chassis connection. The other has a return cable for the negative. Just remember the fuse at the positive batter terminal.
 

Scout

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How do i determine the size wire and fuse size between the battery and fuse block?add up the amp draw of all my devices?
 

John61CT

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Yes be conservative (high) about the total possible amps loads, charging or using.

Get a string and measure actual distance of the wire path in feet.

Blue Sea Circuit Wizard is the bomb.
 

Weight

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The fuse block has a rating. My 6 circuit Blue Sea is rated at 100 amps. It is 15 feet from my battery. I used the 4awg marine wire I had in the shop. I used a 150 amp fuse at the battery terminal, because the wire can safely handle 160 amps away from the engine heat. The Rule; Fuse to protect the wire.
 

John61CT

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But if you *know* the loads are going to be a tiny fraction of the overall block rating, the feed wire and upstream fuse can always be lower. No point spending hundred$ more on heavy copper unnecessarily.

Would be good idea to clearly label things, and of course the "outbound" fuses and wiring from the block should also be sized appropriately small to avoid confusion.
 

B and C

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The upside of bigger wire is less voltage drop in a given distance. Both legs (+ and -) need to be added together to get the length of the electrical path. A 7 foot positive feeder becomes 14 feet long when added to the return path. There are online calculators to help figure the voltage drop in a given wire size over a given distance. A bigger fuse also has less resistance in the circuit than a smaller fuse. Big feeder wire to the block and wire/fuses to fit the load at the end.
 

Scout

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I should probably go bigger than my loads so i can add things later, but probably not to the full capacity of the fuse block.
I found some wire that doesn't cost too much at tractor supply. They arw made to connect batteries together and have the ends that fit 6v batteries already on them. I found 2 lenths of 2/0 gauge (9 and 12") I can use to connect my batteries. Then I was thinking maybe using the smaller gauge which i think was 2 or 4 ga, between the battery and fuse block. The blue sea chart says i can go up to 10ft with 3% drop. Is that overkill? I guess overkill on the wires isnt a bad thing if the price is right. How would i put a fuse into one of those premade wires? Maybe find one that bolts directly to the battery and has a stud on it to accept the wire, or cut the wire and find one that has female ends and a set screw. I think i saw the second kind on a solar kit. How would you do that?
 

Scout

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B and C said:
The upside of bigger wire is less voltage drop in a given distance.  Both legs (+ and -) need to be added together to get the length of the electrical path.  A 7 foot positive feeder becomes 14 feet long when added to the return path.  There are online calculators to help figure the voltage drop in a given wire size over a given distance.  A bigger fuse also has less resistance in the circuit than a smaller fuse.  Big feeder wire to the block and wire/fuses to fit the load at the end.

Thanks i didn't realize the return had to be included. I'm trying to keep everything close to the battery so i can run less big wire and longer small wire.
 

DLTooley

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I’m now installing the blue sea 6 circuit with negative ground. I was looking at installing a master circuit breaker on the fuse panel to also have a master off switch but couldn’t figure out how to mount it safely.
 

Scout

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DLTooley said:
I’m now installing the blue sea 6 circuit with negative ground. I was looking at installing a master circuit breaker on the fuse panel to also have a master off switch but couldn’t figure out how to mount it safely.

I wonder if you could use one of those battery isolator switches. I'm not expert just a guess so verify before you try it.
 

tx2sturgis

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We had those square battery terminal fuses on our OTR trucks, they were for the higher wattage inverters. 

If you go that route, be sure to carry a couple of spares...the normal hardware stores and box stores usually don't have them.
 

John61CT

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Both bank fuses and master isolation switches should be very close to the bank.

Circuit breakers get way too expensive for decent quality at high amps, plus complexity, different speed ratings etc, fuses much more KISS.

High current fuse types include Class T, MRBF terminal fuses, and ANL.
 

Scout

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Those are exactly what i pictured in my head. I've never saw them before but that will work for me.
The wire i found at tractor supply was sae sized not awg. I think it will still work i just know there is a difference maybe slight. But if i go 2 or 4 guage that should be plenty right?even if its sae or awg
 

Canine

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I like to oversize a bit on wire. That 3% drop rating is if everything else is perfect, connections are just right, no fuses considered, etc. Every time you add a switch, a fuse, or a connection of some sort, you get some resistance; therefore, more voltage drop. If you are at a rated 3% voltage drop, it will be more of a drop in reality. So I oversize to compensate for other points of resistance and any mistakes I make in crimping, etc. It does cost more because wire ain't cheap, but my system is small. Every watt helps.

That doesn't mean I'm going to use 3/0 wire for a 2 amp, 12 volt light. I will, however, go up a size or two.

Another thing to consider is how much time will the item be on? I have a hot pot, a high draw item of 1000 watts and I use it only 3 minutes per day with a 6% voltage drop- that is great. I would not get a larger gauge of wire. I could go to a larger wire and get a 1% voltage drop, but the .21 amps per day I would have saved is too small to consider. No way is it worth the money to save that small amount of electricity.
 

tx2sturgis

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I like to use the inline ATC MAX (or Maxi) fuse holders. These are somewhat weather resistant, good for under hood or anywhere, and can be placed in a battery box with no worries of corrosion. No exposed metal means less chance for sparks and shorts when working around them with tools. 

The fuses look like common ATC fuses but are twice the size, and are easy to find in the mid range, (30 to 50 amps) and fairly inexpensive. 

Or, they can be ordered from online sources, up to 100 amps. 

I just installed one on my new truck camper in the battery box, for the supply line that goes to the Blue Sea fuse panel.
 
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