Battery fuse

[sixty9cobra]

I had to move my battery to the trunk to make room for a bigger radiator. I put a Moroso shut off on the battery box. I was wondering if I should put a fuse close to the battery. I have a 200amp fuse do you think that would be big enough to crank a 464 with a Robbmc starter?



                                      Harry

[6667fan]

I think the size of the cable will be the determining factor as far as cranking ability. What did you run?

[sixty9cobra]

I ran 1/0 gauge.

[Jb427]

1/0 is on the small side bigger the better I think I am running 3/0 may even be bigger don't forget you want the earth wire big too. A friend with a 69 mustang mounted his starter solenoid in the boot too that helped him.

[Stangman]

I believe 1/0 wire is thicker than 3/0 wire. I think 1/0 wire is fine, welding wire with the fine wire inside is better.

[Jb427]

1/0 is 8.25mm 3/0 is 10.4mm core size

[66BirdMike]

1.0 copper is good for 150A
3.0 copper ia good for 200A
Your breaker should always be a tad under the rating of the wire, so that it trips before the wire burns up.

[pbf777]

I was wondering if I should put a fuse close to the battery. I have a 200amp fuse do you think that would be big enough...................                                     

      It would seem that a fuse would be a good idea, but it isn't standardly practiced; consider it somewhat as the electrical service drop coming from the utility company power pole to the service/weather head on your house (even to the service disconnect) as this is, as a singular circuit, unfused. 

      And as far as to the ampere value required, check the amp draw on cranking (hot), I think you'll be surprised to find that 200amp just might not cut it!   

      An additional consideration, or perhaps confusion, particularly in the observation of this automotive wiring execution, that as often practiced by the O.E.M.'s, is that they understand that this is an 'intermittently' high amp circuit (only when the starter motor is engaged) and with that understanding they take advantage of the heat sink capacity of the wire thereby allowing over-amping the wire for short durations.  Proof, is in if you operate the starter for excessive durations, or ever had a starter out of your control stuck in the cranking mode, the wire lead to the starter will get hot or even literally melt and burn the insulation off the cable!   

      The same limited duration "over-amp" loading of the circuit (cheating! ) is also practiced in other equipment and structures and is typically addressed with "time-delay" or "slow-blow" fuses and circuit breakers; and this is another consideration in the inquiry of: "is this fuse big enough"?   

      Scott.

[WConley]

Re: Over-Amping

Charles Kettering first hit upon this principle when he invented the electric starter in 1912!  All of the experts told him that no available electric motor could provide that kind of torque in a reasonable size to package for a car.  Kettering realized you could over-drive the crap out of a small motor for a short time, if it had enough thermal mass to absorb the heat.

[Tommy-T]

Yes
A 200 amp fuse in the cable to your starter solenoid is plenty.
My Comet is wired like your Mustang. 1/0 cable from the front to back with a 200 amp Mega fuse next to the battery.
Of equal concern is the grounding especially if you've got electric fans, hi amp ignition box, high amp draw starter, or other heavy draws. In the old days we all just welded a nut to the subframe inside the trunk and made a short cable, same size as the cable to the solenoid, and screwed it down.
More modern thinking, especially if an electronic fuel injection system might be in the future, is to run the ground cable, same size as the cable to the solenoid, to the engine block and then to the chassis at the front. Yes, it's cumbersome and heavy to run 2 cables from the front to back of the car. It is amazing to note how poor steel is a conductor of electricity compared to copper or aluminum.
Could help avoid electrical "gremlins" in the future.
Grounds,Grounds,Grounds!

[Jb427]

Yes
A 200 amp fuse in the cable to your starter solenoid is plenty.
My Comet is wired like your Mustang. 1/0 cable from the front to back with a 200 amp Mega fuse next to the battery.
Of equal concern is the grounding especially if you've got electric fans, hi amp ignition box, high amp draw starter, or other heavy draws. In the old days we all just welded a nut to the subframe inside the trunk and made a short cable, same size as the cable to the solenoid, and screwed it down.
More modern thinking, especially if an electronic fuel injection system might be in the future, is to run the ground cable, same size as the cable to the solenoid, to the engine block and then to the chassis at the front. Yes, it's cumbersome and heavy to run 2 cables from the front to back of the car. It is amazing to note how poor steel is a conductor of electricity compared to copper or aluminum.
Could help avoid electrical "gremlins" in the future.
Grounds,Grounds,Grounds!

I run + and - to the front of my car I did have hot cranking problems at first with a std size cable not sure exactly the size was not smaller then 1/0 I went bigger when I added a battery cut switch not had a problem after that. Not sure if it had anything to do with fixing my problem but it seemed to help with hot cranking when my high draw fans are starting at the same time.

[pbf777]

A 200 amp fuse in the cable to your starter solenoid is plenty.  My Comet is wired like your Mustang..............

     Note that although some executions may work for some, they may not for others!   

      And as far as to the ampere value required, check the amp draw on cranking (hot), I think you'll be surprised to find that 200amp just might not cut it!   
 

     I have witnessed many an instance, for whatever reason, where the amp-draw at cranking surpassed 200 amps! 

     Scott.

     

[cammerfe]

Regarding cable, it has been my experience that welding supply companies often have a bin somewhere with odd bits of cable that, while short for setting up a good-sized stick welding installation, are very useful around a car. I tend to use 'double-aught'.

It is, I think, still possible to find the sort of battery solenoid that has a lock-unlock mechanism built in. Put it next to the battery. (Using a'regular' Ford-type invites overheating because they're not rated for constant use.) One that has been modified to latch can be connected so as to have the cable live only when the engine is running.

All ground runs should also be the same sort of welding cable. Crimp AND solder and use the sort of shrink tube that has heat-activated adhesive on the inner surface. Go from battery ground to a frame rail and use battery post grease in the connection to deter oxidation. Do the same thing from the front of the frame to the engine block. Now you have a proper circuit lay-out.

Properly wired, the latch-solenoid also makes a dandy anti-theft device.

KS

[sixty9cobra]

Ok Ill install the fuse and if it's a problem I remove it, Lots of knowledge on here thanks for the opinions.

[MeanGene]

When we set up the trunk-mounted battery in my 406 car in 1977, the first engine going in was a 14:1 427. My buddy was the warehouse manager for a local electrical contractor that also sold to the public, and I pitched for their softball team, so we went down on Saturday and went dumpster diving. Came up with a long scrap of 4/0 aluminum wire, which is of course a lot lighter than copper. A few lugs and borrow the hydraulic crimper, ran it along the frame rail to a solenoid mounted on the firewall close to the starter, ground right under the trunk to the frame. A piece of heavy welding cable to the starter. I had an old rebuilt 302 starter laying around, so I swapped an FE 3-bolt flange onto it and plugged it in. Spun the crap out of the 14:1 engine, hot or cold, and is still in the car today with a 12:1 engine, will start it easily with a 24F battery
There are heavy duty solenoids that look like a Ford stocker that are designed for high amperage constant duty, one use is in the cranes on service trucks- my buddies with mobile mechanics trucks usually carry a couple spares
Somewhere I have my gramps' old current draw meter (pre- clamp on guage by decades lol) that just has a sheet metal channel that fits over the cable to measure amp draw on the starter cable. He had three M35 "deuce and a half" trucks (Two REO's and a Studebaker) in his fleet. Those were equipped with the military 24-volt systems, and he used that guage when converting them to 12-volt. Now I gotta look for it lol