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Discussion Starter · #1 ·
My 63 has the battery relocated and I want to put a fuse there in case the wire gets damaged and grounds out. Not sure why there isn't one, but I kinda think there should be.

What size main fuse would you run and any links to a setup?

Thank in advance!

-Paul
 

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I've done this before, and I'm about to tackle this on a screwed up post-war Mopar that had the battery relocated to the trunk. Not a Nova, but the concept is the same. I'm at the parts ordering phase for this one.

For fuses, there are two choices. The "Mega Fuse" style fuses go up to 300A, and 300A is generally enough for the starter cable. If you need more than 300A, there are "post fuses" (AKA "terminal fuses") that go on a 3/8" post. which are useful. Those are more common in marine applications, and can be found online.

Also, where the battery cable passes through a metal body panel, use a "pass through" connector. I prefer Moroso 74144, available at online speed shops (Summit, Jegs, Speedway Motors) or Amazon. If Red isn't your thing, it's available in black as Moroso 74145. The pass through is an excellent place to mount a terminal fuse block with a terminal fuse.

And be sure to put rubber boots on the cable ends, especially the ones under the car, exposed to weather.

You can power the fuse block(s) from the alterntor post, or from the starter post, but I prefer (a) separate MegaFuse(s) in the trunk, one for each fuse block, and separate power wires of appropriate size run from the megafuse near the battery (in the trunk) to each fuse block. This makes diagnostics easier down the road. I do generally run the alternator charge wire to the starter post, with a fusible link at the starter end of that cable, or a mega-fuse on the firewall sized to match the alternator. .
 

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What gauge wire do you have run already ?

Is it copper or copper clad aluminum wire ?

Is the motor cranking over fine now ?

The reason for my questions are is that fuses get sized to the gauge and type of wire.

If for some reason the motor is not cranking over good now and this is from undersized cabling then you may be popping fuses too often (or what one might call nuisance blows).

Anyway, there are charts out there to size fuses to wire gauge.

Personally I use the following fuses for copper stranded wire:

10 gauge/30A or less fusing
8 gauge/60A or less fusing
4 gauge 150A or less fusing
2 gauge/200A or less fusing
1/0 gauge/300A or less fusing

On my 73 Nova custom I have a 300A fuse on 1/0 copper wire for the starter and then a 200A one on another 1/0 wire for my 200A alternator and not had any issues.

Jim
 

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There are also high current circuit breakers at 300a and up with threaded posts to make secure and safe mounting easy.
My least favorite setup is the "trash can relay" or "Ford" relay that is used to make the heavy gauge starter wire only active during cranking. It works but it's also somewhat of a band aid as you will need to run another constant energized wire anyways to power the fuse block. This wire will need to be around 8ga or larger. So for this setup to work (which is arguably safer) you have double the work and additional connections (points of failure). Check out mad electrical for ideas and diagrams. I personally believe the way the general did it back in the day is just fine as long as safe and proper techniques are used when wiring the vehicle. A high current or fuse or circuit breaker a decent safeguard to protect the wire and possibly the vehicle.
 

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Discussion Starter · #7 ·
There are also high current circuit breakers at 300a and up with threaded posts to make secure and safe mounting easy.
My least favorite setup is the "trash can relay" or "Ford" relay that is used to make the heavy gauge starter wire only active during cranking. It works but it's also somewhat of a band aid as you will need to run another constant energized wire anyways to power the fuse block. This wire will need to be around 8ga or larger. So for this setup to work (which is arguably safer) you have double the work and additional connections (points of failure). Check out mad electrical for ideas and diagrams. I personally believe the way the general did it back in the day is just fine as long as safe and proper techniques are used when wiring the vehicle. A high current or fuse or circuit breaker a decent safeguard to protect the wire and possibly the vehicle.
That's my goal in the end. The car does fine on it's own, I just want to make it better :) I mean, what could go wrong with a wire run form the back to the font and no interrupter at the battery.

I am looking for a good relay now. Starting with Mad Electrical - thank you sir!

Thanks to Custom Jim as well for the guidance :)
 

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Like Geoff said, less connections the better but on my 73 Nova Custom I have the battery in the back with a 300A fuse on it going to a 200A/300A relay/solenoid that then connects to a 1/0 copper wire which then goes to my starter which then has the solenoid on it jumpered.

I then have a 200A fuse going to yet another 200A/300A relay/solenoid which then has a 1/0 wire off of it going to my 200A alternator.

How I have mine setup is when the key is off there are no hot terminals under the hood to where I can safely wrench on things like the starter wiring, the alternator wiring, and such and not have to worry about things being hot or live.

Granted my electrical system on that car is not standard but it has all of the fusing, relays, and bus bars in the trunk as well as having dedicated wires run from things like the headlight grounds, the wiper grounds, the turn signal/parking light grounds all run back to the trunk to where I'm not relying on the headlights getting a ground from the radiator support that then is bolted to the fenders which then are bolted to the firewall and then this metal section is spot welded to may other pieces to where eventually the ground got back to the battery through all of those connections.

Maybe do a search too on the site as I'm not a fan of breakers but there are plenty of large amperage fuses out there today and one I bought, and have yet to try out, is a 300A cube fuse. It takes a special holder but the footprint is the smallest I've seen so far.

Partially asembled and with a 150A fuse:



Assembled:



Or another style they offer:


Jim
 

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The car does fine on it's own, I just want to make it better :) I mean, what could go wrong with a wire run form the back to the font and no interrupter at the battery.
Below is a Camaro from Drag Week 2014 that the main cable shorted to ground and then filled the interior with smoke while they were driving down the road. The true hot rodders that they were then took some jumper cables and ran them outside the car to get them to the next stop.





Jim
 

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Custom Jim always good info! I know you know your wiring! I did audio install stuff for many many years and have seen all kinds of failures from poor practices. I also worked at an FAA repair station on aircraft systems including electrical. The Ford relay starter wire isolation setup is actually very similar to the "master contactor" used in aircraft. But like we've both mentioned the way the cars were setup is fine and adding a fuse or breaker gives peace of mind. Thanks for sharing the info and photos on the guys with the failure at the battery.
 

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In terms of "wire damage", you're largely wasting your time and money by fitting fuses on the heavy gauge stuff. It's far more likely for some minor chaffing to expose enough conductor to short, and heat up enough to start a fire without coming even remotely close to pulling enough amperage to pop the fuse or breaker once you get up into fuses of hundreds of amps.

On the other side, if you manage to get enough damage to pull that 300+ amps, you're going to kill the battery in a very short amount of time, which will effectively do the same thing that a popped fuse would anyways. Whereas a typical battery will supply 25amps through a direct short on a smaller wire for plenty enough time to start a fire.

This is largely the reason you don't find the heavy cables to be fused in an OEM application, or large draw aftermarket accessories like winches, though many people add them anyways to feel better.

You're much better off going the extra mile to ensure that the big cables are extremely well protected to prevent the damage in the first place.
 

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While there will always be discussions as to whether to fuse or not to fuse, you see more and more protection being built into vehicles these days.

We can also have discussions as to vent or not to vent a battery to the exterior of a vehicle when the battery is in an enclosed area like a trunk or interior.

Think back years ago and no cars had fusible links but then as things evolved they got installed.

Years ago too, no one that I can think of ever fused the main starter cable off of a battery but yet today more and more vehicles have fuses in place on the cabling off of a battery.

While we will all have different views of things, I'm not going to run an unprotected wire or cable in my car if I'm designing it.

Here's another photo of a big rig battery that the main cable got pinched:



Just to back up how some vehicles are being designed to have main fuses for the starter (and other large draw devices) here are some pictures I've saved:

2019 Camaro:



Chevrolet Cruze:




Jaguar:





On a ship:




An interesting video to watch as the person took an 8 gauge wire protected by a 300A cube fuse and when the 8 gauge wire was shorted to ground, the wire passed over 1000A for a split second but then the fuse blew and no wire damage occurred.



And one last thing, is I don't care how well I could or would run a cable from the trunk to the front end of the car, if for some reason I would get T boned and my properly run cable were to be smashed and sliced to connect to ground, I would like to see my $15.00 fuse do it's thing and disconnect power from the short.

Jim
 

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Thanks for the pictures of the newer car wiring,! Very interesting. As for the discussion on wether to fuse or not I wonder if there is some sort of mandate?

Look at the red heavy gauge cable in the Cruze. No heat shrink and the copper is visible. That drives me crazy my 2¢
 

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Thanks for the pictures of the newer car wiring,! Very interesting. As for the discussion on wether to fuse or not I wonder if there is some sort of mandate?

Look at the red heavy gauge cable in the Cruze. No heat shrink and the copper is visible. That drives me crazy my 2¢
that bolt on there certainly does not look stock...

Audio equipment Electronic engineering Electrical wiring Computer hardware Circuit component


But apparently the cable is stock... WHAT A PILE!!!

Auto part Machine Automotive exterior Toy Bumper
 

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Thanks for the pictures of the newer car wiring,! Very interesting. As for the discussion on wether to fuse or not I wonder if there is some sort of mandate?

Look at the red heavy gauge cable in the Cruze. No heat shrink and the copper is visible. That drives me crazy my 2¢
I guess they didn't want to keep driving you crazy so they made it with a hinged plastic top cover.

A backed off picture of the assembly with the lid open:



Jim
 

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That Cruze panel could definitely be integrated into older car for circuit protection. The ship one might be a tad overkill

Some Polaris battery cables are the same way with no heat shrink on the exposed copper
And they tend to operate in harsh conditions
 

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I have a 200 amp marine type resetable circuit breaker in my trunk mounted external to the moroso battery box so I can access it easily. I used #2 welding cable to run to engine compartment insulated distribution bar. From this distribution bar I have the same size cable going to each the starter and 150 amp alternator. I also refed the existing horn relay feed with #8, and a new small marine type 6 circuit fuse block mounted beside the distribution block with #8. This new fuse panel feeds my electric water pump, dual fans, and air conditioner circuits. All are fused appropriately per manufacturers recommendations. This keeps any new loads off of the existing fuse panel, and makes ease for trouble shooting under the hood for the big load items. I've had no problems with this setup so far.
If I over crank the starter very long the circuit breaker will trip, and need reset after about 5 minutes. Saves over heating starter and associated circuitry. This circuit breaker is an easy way to kill power to work under the hood too. It has a button on it to manually trip it out.
 
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