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Hot Rods Battery fuse

Discussion in 'The Hokey Ass Message Board' started by Kevin Ardinger, Jan 12, 2020.

  1. Kevin Ardinger
    Joined: Aug 31, 2019
    Posts: 778

    Kevin Ardinger
    Member

    Anyone run a fuse on the positive cable? I’ve seen a lot of pick of hot rods burned to the ground. I suspect it was from poor wiring. If so, what size fuse? I’m thinking of a inline fuse on the positive cable. I have a battery shutoff on the negative cable. Any advice would be appreciated.


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  2. Boneyard51
    Joined: Dec 10, 2017
    Posts: 6,442

    Boneyard51
    Member

    Use a mega fuse, they come in 250,350, amp. If you want more amps you can stack the fuses to increase amps. I don’t think they recommend it , but I have done it with success before. Not on a starter circuit, but on a very high amp draw circuit.






    Bones
     
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  3. Kevin Ardinger
    Joined: Aug 31, 2019
    Posts: 778

    Kevin Ardinger
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  4. squirrel
    Joined: Sep 23, 2004
    Posts: 55,945

    squirrel
    Member

    Keep in mind that a fuse in battery cable connection will only protect the car from burning down to the ground in event of the positive cable shorting to ground. It won't do a damn thing for all that other wiring that is not done right.

    Be sure to add an appropriate size fuse to the smaller wire that connects to the battery or cable, and feeds the rest of the system.
     

  5. Boneyard51
    Joined: Dec 10, 2017
    Posts: 6,442

    Boneyard51
    Member

    Depends on your engine and starter. If it’s a big inch high compression Chevy with a stock starter you will need 500 amp fuse to survive. If it’s a low compression four cylinder 150 will get the job done.






    Bones
     
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  6. BJR
    Joined: Mar 11, 2005
    Posts: 9,818

    BJR
    Member

    I run no fuse from the battery to the starter, but the main feed from the starter to everything else goes through a 60 amp fuse. Works just fine for over 5 years now.:D
     
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  7. The37Kid
    Joined: Apr 30, 2004
    Posts: 30,629

    The37Kid
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    Does anyone know where and why all the extra juice is created in the first place?

    Bob
     
  8. squirrel
    Joined: Sep 23, 2004
    Posts: 55,945

    squirrel
    Member

    Is ALL the wiring that is protected by that fuse, large enough to blow the fuse before the wire gets too hot and starts a fire?

    I'd probably be looking over the wire sizes and see what fuses might be more appropriate.
     
  9. squirrel
    Joined: Sep 23, 2004
    Posts: 55,945

    squirrel
    Member

    That's an interesting question, and really doesn't make any sense.

    A car battery can provide a LOT of current, for a short time, if the load is low enough resistance. For example, if you connect the positive and negative terminals to each other with a big, short, fat wire, you will probably get between 1000 and 2000 amps through the wire, for a very short time--before something violent happens. That's just the nature of a car battery.

    But the "extra juice" is not used most of the time. The current that flows from the battery depends entirely on the load you apply to the battery.
     
  10. Hnstray
    Joined: Aug 23, 2009
    Posts: 12,355

    Hnstray
    ALLIANCE MEMBER
    from Quincy, IL

    The 60 amp (or capacity of your choice) is only the first line of defense. That wire normally supplies current to the distribution panel which then has individual, or small groups, of circuits protected by a fuse.

    IMO, unless the battery is remotely mounted, with a long + cable subject to potential damage, I really don’t see much reason to fuse the battery to starter connection. Routing it, or the ground side, through a switch for anti-theft deterrent is a separate matter.

    Ray
     
    Last edited: Jan 12, 2020
  11. Mr48chev
    Joined: Dec 28, 2007
    Posts: 33,861

    Mr48chev
    ALLIANCE MEMBER

    There is your answer right there. The same difference as a fusible link in any GM car since at least the early 70's and most other rigs straight from the factory. You do need to figure out what the standard amp load for the accessories you would power off it would be.
    Big amps or other big draw add on items usually have their own separate fused from the battery power supply that doesn't depend on the regular vehicle supply anyhow.
    With that the correct fuse holder/block to put a fuse in your power supply for the main fuse box is probably hanging in a blister pack at your local car audio store.
     
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  12. Kevin Ardinger
    Joined: Aug 31, 2019
    Posts: 778

    Kevin Ardinger
    Member

    Yeah all the smaller wires are fused properly. I used a painless harness and their recommendations for fuses. My positive cable runs from rear of car to the front along the right rocker panel. (Model a sedan) the cable is run neatly and secured, I’m just a little concerned if it were to rub something sharp.


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  13. Hemi Joel
    Joined: May 4, 2007
    Posts: 1,528

    Hemi Joel
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    from Minnesota

    I agree with Jim, a battery fuse will protect nothing except the cable from the + battery to the starter solenoid, or where ever else it is routed to. A battery cable fuse would just have too high of a capacity to protect any of the smaller wires downstream. Better than a fuse, just make sure that your battery cable is well-routed, not chafing or rubbing on anything that will wear thru the insulation, not close to a heat source, and protected from being pinched by any moving parts such as steering and suspension. When I have had to run a cable all the way to the rear of the car for a trunk mounted battery I've actually put the battery cable inside of a hose for extra protection.

    Then make sure that all of the rest of the smaller wires throughout the car are well routed and well protected in the same way, and use appropriate sized fuses for them. The other thing for fire protection is make sure that all of your fuel lines are in good condition and well attached. Personally I would tend to think that more fires are caused by fuel leaks than by electrical. Usually an electrical short burns up a wire pretty quickly and then it cools off quickly.
     
  14. Boneyard51
    Joined: Dec 10, 2017
    Posts: 6,442

    Boneyard51
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    I think some folks have missed to OP question. OEMs don’t fuse the cable to the starter because it is usually rather short, well insulated and has little chance of shorting out. The OP is going to put his battery in the trunk and run the positive cable the full length of the car. And was wanting some protection from a possible short as to not burn his car down. A very reasonable request. He never said he was going to use that as his only fuse!
    What I would recommend is the way a Hamber posted in another post. Put a relay near the battery and only excite the starter wire when starting the car. Then run an eight gauge wire back to grab your power for the rest of the car and put a sixty or so fuse in it!








    Bones
     
  15. Kevin Ardinger
    Joined: Aug 31, 2019
    Posts: 778

    Kevin Ardinger
    Member

    That’s a great idea Bones. That’s what I was looking for.
    Thank you


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  16. Mimilan
    Joined: Jun 13, 2019
    Posts: 1,230

    Mimilan
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    That was my posting .
    Here! I even drew a rough[ish] schematic to follow.

    https://www.jalopyjournal.com/forum...ectrical-run-too-close.1180264/#post-13402869

    I even added a diode to the charge/alt wire [for when you wear metal watch strap while working in the engine bay :D]
     
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  17. Boneyard51
    Joined: Dec 10, 2017
    Posts: 6,442

    Boneyard51
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  18. Boneyard51
    Joined: Dec 10, 2017
    Posts: 6,442

    Boneyard51
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    Thank Mimilan! I got it from him!








    Bones
     
  19. Mimilan
    Joined: Jun 13, 2019
    Posts: 1,230

    Mimilan
    Member

    Thanks for the vote of confidence.

    It wasn't my idea........Just my posting. Road racers [FIA sanctioned] have been using this for years

    Now that trunk mounted batteries are common on Hotrods , it would be a "no-brainer" to add a $15 solenoid [which fixes Chevy heat-soak issues at the same time]



    Edit: I've done a variation of this [for Racing] where I used 2 batteries in series [24 volt] to start.
    But it charged the 2 batteries parallel [12 volt] through the stock harness
    This was a necessity on old English Fords with Lucas starter motors. As soon as you raise the compression they really struggled.

    This would probably be of interest for the 6 volt crowd
     
    Last edited: Jan 12, 2020
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  20. Hemi Joel
    Joined: May 4, 2007
    Posts: 1,528

    Hemi Joel
    Member
    from Minnesota

    An easy, simple solution is to add another layer of protection by running the cable thru a reinforced hose, such as a heater hose, or gas hose, then re-secure it. I've done that before with a trunk mounted battery. (and trailer tongue wiring, too)
     
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  21. Jalopy Joker
    Joined: Sep 3, 2006
    Posts: 31,180

    Jalopy Joker
    Member

    one of the first stages of protection is have a fusible link in primary wire for alternator - the diodes can fail and short and create conditions for fire - a friend had this happen to his ride in his garage - also, install a good quality kill switch in system - if not driving your ride on a regular basis helps protect battery drain too, when switched off
     
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  22. jaracer
    Joined: Oct 4, 2008
    Posts: 2,419

    jaracer
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    By relay I assume you mean a starter solenoid like the older Fords. It would have to be large enough to carry starter current.
     
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  23. Mimilan
    Joined: Jun 13, 2019
    Posts: 1,230

    Mimilan
    Member

    Yes .... A Ford Solenoid [AKA Starter Relay elsewhere in the world]
     
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  24. Boneyard51
    Joined: Dec 10, 2017
    Posts: 6,442

    Boneyard51
    Member

    That’s where terminology comes in, and it can be regional. To me the “ switch” on a Chevy is a solenoid, as it moves something and makes electrical contact. On a Ford, the “ switch” only makes electrical contact, that makes it a relay. But a lot of people use “ solenoid” interchangeably.

    Also on the 12/24 or 6/12 systems trucks and tractors have been using this start/ run system for years successfully. It takes several “ relays” or one big expensive multipost relay to get the job done. Starters like voltage. I’ve been using a six volt starter on a 12 volt system for years with no problem.






    Bones
     
    Last edited: Jan 13, 2020
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  25. Yep . . . Sometimes it's really helpful to use consistent, correct, terminology. ;)
     
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  26. I have been known to use a fusible link on the main hot wire after the battery cable. They are cheap enough and genuine car wiring stuff. I cannot see any reason to fuse the battery cable. As long as you are not burning the insulation off the cable and grounding it out it should not be necessary.
     
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  27. jaw22w
    Joined: Mar 2, 2013
    Posts: 1,671

    jaw22w
    Member
    from Indiana

    Fusible links have been mentioned here once or twice. What is the criteria for using a fusible link as opposed to a circuit breaker or fuse? Seems to me that using a fuse or breaker would give one less chance of starting a fire. I do wire my own cars, but I'm not really very electrically minded. None of my cars have fusible links in the system. Can some one straighten me out?
     
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  28. Boneyard51
    Joined: Dec 10, 2017
    Posts: 6,442

    Boneyard51
    Member

    The fuseable links were cheaper than fuses or circuit breakers, that’s why OEM used them, that’s also why a hot rodder shouldn’t use them. Saving a couple of dollars here , could cause some trouble.....or not! I just don’t like fuseable links. As far as that goes, I don’t like fuses...... I’m a circuit breaker, kind of guy!

    Cars back before , say about 1970 or so, didn’t have any protection here. The main feed was not fused, just like the starter cable, was not fused.






    Bones
     
    Last edited: Jan 13, 2020
  29. Kevin Ardinger
    Joined: Aug 31, 2019
    Posts: 778

    Kevin Ardinger
    Member

    This shutoff switch I have says it has a 20 amp sustained fuse and a 150 amp momentary fuse. What does that mean? Its a Mister Gasket battery shutoff switch.
     
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  30. Boneyard51
    Joined: Dec 10, 2017
    Posts: 6,442

    Boneyard51
    Member

    Just like it says, it will flow up to 20 amps all day and 150 amps for a short time. It has a fuse in the switch? Maybe that’s just the switch rating?




    Bones
     
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