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Technical Battery cable size?

Discussion in 'The Hokey Ass Message Board' started by 53 hemi, Jan 15, 2021.

  1. Gearhead Graphics
    Joined: Oct 4, 2008
    Posts: 3,852

    Gearhead Graphics
    Member
    from Denver Co

    I ran 00 welding cable on my bucket, and ran a 4awg ground cable from the starter back to the battery. Yeah Its overkill. But you can definitely hear the difference in the starter with the ground on battery vs ground on frame. And, I'd already ran the 4 as the positive side and it just didn't cut it, so might as well repurpose it
     
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  2. Make sure it's not aluminium instead of copper, many jumper cables are. Doesn't work well.

    Sent from my moto g(8) power using The H.A.M.B. mobile app
     
  3. 51504bat
    Joined: May 22, 2010
    Posts: 3,040

    51504bat
    ALLIANCE MEMBER

    Great chart . Bookmarked it. Thanks for posting
     
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  4. blowby
    Joined: Dec 27, 2012
    Posts: 7,960

    blowby
    Member
    from Nicasio Ca


    Definitely copper, had to put on new terminals. Didn't use the clamps. :)

    I've saved many jumper cables that came in the trunks of vehicles, good wire for various other uses. And the wire size does vary from ridiculously small to good size. Haven't run across aluminum yet though but I'm sure it's out there.
     
  5. H380
    Joined: Sep 20, 2015
    Posts: 463

    H380
    Member
    from Louisiana

  6. ekimneirbo
    Joined: Apr 29, 2017
    Posts: 2,109

    ekimneirbo
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    from Brooks Ky

  7. Rynothealbino
    Joined: Mar 23, 2009
    Posts: 249

    Rynothealbino
    Member

    When I wired in the rear battery for an OT vehicle (also runs a front winch) I used 1/0 welding cable. Seems to do the trick so far and is way easier to work with than regular battery cable. 1/0 is the biggest I could get inside of 1/2" EMT conduit, which I ran in a couple spots for protection. Heat shrink the ends in to seal it. I would also recommend having an easily accessible shut off switch just in case. I just went down to the welding shop and bought it by the foot. Call around, I'm sure someone near you stocks various sizes. Finding red might be tricky, I just put red heat shrink on the ends of the positive cable.
     
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  8. Deuce Daddy Don
    Joined: Apr 27, 2008
    Posts: 5,228

    Deuce Daddy Don
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    ALL good comments!------Like others I used welding cable size from battery in trunk to engine, has worked great for the last 300,000 miles now!
     
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  9. Boneyard51
    Joined: Dec 10, 2017
    Posts: 5,196

    Boneyard51
    Member

    Did you put a dedicated ground for that winch?






    Bones
     
  10. Gregm1
    Joined: Dec 16, 2020
    Posts: 22

    Gregm1

  11. Mr48chev
    Joined: Dec 28, 2007
    Posts: 30,056

    Mr48chev
    ALLIANCE MEMBER

    These pretty well Explains it. Years ago when I was teaching high school auto mechanics I still had the old records an film strips that Mopar used in their dealer mechanic training in the early 50's. It in rather comical fashion explained volts, amps and ohms and how they worked in a car.
    The concept hasn't changed since though.
    Volts = the pressure.
    Amps = are the amount of flow.
    Ohms = is the resistance to the flow.

    Then throw in the fact that each foot of wire has X amount of resistance and the way you reduce resistance in that foot is increase the diameter of the wire.

    Comparing 6 and 12 volt batteries a six volt doesn't have the pressure to push the amps though the resistance of a smaller wire that a 12 Volt does.

    That said, when we have a 12 Volt system making certain wire and cable sizes larger reduces the resistance in the wire and bypasses the (It's 12 Volts you only need) idea. The larger cable lets the amps flow from the battery with less pressure from the battery being needed or used up pushing the amps though the cable.

    Electricity-101-v2.png Elictricity explained (2).jpg
     
  12. Rynothealbino
    Joined: Mar 23, 2009
    Posts: 249

    Rynothealbino
    Member

    Bones, I did not run a dedicated ground. Are others running one? I have no problem cranking in gear under load either.
     
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  13. AHotRod
    Joined: Jul 27, 2001
    Posts: 11,554

    AHotRod
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  14. 53 hemi
    Joined: Jan 8, 2009
    Posts: 492

    53 hemi
    Member

    Thanks, everyone. I've ordered a 7' length of marine grade 2/0.

    Sent from my SM-G950U using The H.A.M.B. mobile app
     
    Last edited: Feb 1, 2021
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  15. Boneyard51
    Joined: Dec 10, 2017
    Posts: 5,196

    Boneyard51
    Member

    Sorry, missed this one! In most vehicles, the ground runs to the engine, from the battery with a large wire, to power the starter. Then smaller grounds go from the engine to the body and another one to the frame. These are usually 12/14 gauge wires used to power lights and small accessories. The ground to the frame is sometimes just for the fuel sender or other small draw items.
    If you use your frame or body for the ground circuit to return to your battery, it will try to use these small wires to power the starter, causing a massive overload for those wires. Sometimes it will find other pathes to ground. I , one time, had a vehicle use the speedometer cable as a high amp path back to the battery, with catastrophic results.
    The solution is to add “ dedicated” grounds, as they are sometimes refereed to. That is a large, I use 00 gauge, grounds from the body and the frame to the negative post on the battery or to the engine. Depends sometimes on access.
    These are lessons learned when I was an outfitter for new trucks, putting work beds on them.


    Edit. Depending on your winch, condition, and load, your winch could draw in the range of 350+ amps. It will find a path to ground if you do not provide one. You may not like the path it finds.





    Bones
     
    Last edited: Feb 1, 2021
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  16. 427 sleeper
    Joined: Mar 8, 2017
    Posts: 1,358

    427 sleeper
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    I've always been under the impression that the thinner strands carried the amperage better than the thick strands. Something to do with more surface area for the electrons to flow over, or some BS... :confused:
     
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  17. Ziggster
    Joined: Aug 27, 2018
    Posts: 920

    Ziggster
    Member

    I recall reading while doing research for my dual battery/ inverter (3,000W) install on my truck, that it was necessary to run a ground cable (1/0 welding cable) back to the battery (inverter was installed in the rear) to avoid any sort of voltage drop. In electrical design you must account for voltage drop even after the load. For DC any voltage drop results in increased amp draw by motors = bad. In my case it was more like 10’ plus back to the inverter. I also added a megafuse at the start of the run near the battery. For a starter motor application it may not be necessary for short durations, but I’ve seen vehicles catch fire from the starter cable when starter solenoids have stuck in the “closed” position. A long unprotected (fused) wire is a perfect source for such fires.
     
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  18. alchemy
    Joined: Sep 27, 2002
    Posts: 17,283

    alchemy
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    Yeah, I've always understood the current flows on the outside surface of the strands. So a million smaller strands have more surface area than a half million larger strands (all carried in the same gauge insulation cover). Granted the thicker strands will make for a stiffer cable that won't droop when clamped to the side of your chassis, so maybe it would be preferred if it will still carry the current you need.
     
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  19. squirrel
    Joined: Sep 23, 2004
    Posts: 49,859

    squirrel
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    That applies to high frequency AC, but not DC.

    Sent from my Trimline
     
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  20. 1971BB427
    Joined: Mar 6, 2010
    Posts: 7,052

    1971BB427
    Member
    from Oregon

    The reason the fine strand wire carries more current in equal sized cable is the density of fine strand wire vs. thicker strands. Less space between strands means more capacity inside the same diameter overall.
    In apprenticeship our instructor told us to think of conductors as water pipes. Electricity flows through conductors like water flows through pipes. Any point of resistance, is similar to a restriction in a pipe. And pipe size dictates how much water can flow, just like wire size dictates how much current can flow.
     
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  21. I used 200 strand Welding Cable when I was Racing & I had some left over
    so when I put the Chevy. engine in my Merc. I used it.
    That was 40 years ago, I even have a Set of Jumper Cable's made with the
    same Wire.!

    Just my 3.5 cents

    Live Learn & Die a Fool
     
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  22. Rynothealbino
    Joined: Mar 23, 2009
    Posts: 249

    Rynothealbino
    Member

    So assuming everything hooks to to what it's supposed to hook to (not trying to ground through a speedo cable or similar) then we can treat a frame rail like a giant conductor right? I assume your average 2x4 frame rail has plenty of current carrying capacity, so then it becomes a question of resistance over say 10 or 12 feet of frame rail between the battery and starter to determine voltage drop right? Anyone have long leads on a multimeter that can accurately measure the resistance across a simulated frame rail? Then we just use Ohms law to figure out the rest. Obviously a dedicated ground would be best but now this has me rethinking some things.
     
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  23. dan31
    Joined: Jul 3, 2011
    Posts: 1,087

    dan31
    Member

    I would like to see that test myself and would also like to see how much of a difference there might be ( if any) between a car with a frame and a unibody.
     
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  24. mrharley51
    Joined: Sep 16, 2007
    Posts: 225

    mrharley51
    Member

    If I am reading and understanding some of the comments: a dedicated ground should be of the same gauge as all your other grounds or you may have some issue with the current following a smaller gauge wire and frying it...that is something to remember for sure.
    Seems to be two schools of thought/practice here; one that ground to starter/engine and
    school 2 grounds short cable runs to frame front and rear...
    I have done both and now only run ground to starter/engine...
    Fiberglass cars must be a real nasty ground challenge...
     
    Last edited: Feb 6, 2021
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  25. AldeanFan
    Joined: Dec 12, 2014
    Posts: 749

    AldeanFan

    The problem I’ve seen is these often the factory grounds the battery to the engine with a large cable and then the engine is grounded to the frame with a much smaller cable.

    So if you use a high draw items like a winch grounded to the frame then the path to ground is frame to small cable to engine to large cable to battery.


    Sent from my iPhone using Tapatalk
     
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  26. Boneyard51
    Joined: Dec 10, 2017
    Posts: 5,196

    Boneyard51
    Member

    I have not done a test with a meter, but have tested in the real world. Mainly we are talking about a battery placed in the rear of a vehicle and all the power needed in the front, necessitating long cables. Using the frame is absolutely no problem if done properly, ie clean tight connections and proper size wire. Using the unibody is also no problem , just make sure you attach your wires to a heavier , structure, spots on the body.
    One company that I represented opted to just use two cables to go to the back of the truck from the battery. They figured it cut down on the connections, for the win! Any of the three ways , done properly will work, your choice. In this instance bigger IS better!








    Bones
     
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  27. That's known as 'skin effect' and as Squirrel noted it's only a factor in AC, not DC. If you're transmitting high voltage/high current AC it can be a factor, but when it is and can be addressed the solution is not wire at all, but hollow tubular buss bar. And almost always made of welded aluminum.

    Welding lead cable is a good choice for our applications as it's very flexible and has an insulation that's very resistant to abrasion and impact damage. Not as good as thermoplastic for extended heat or chemical exposure.

    I've used large aluminum building wire as battery cables in vehicles a few times (there's a considerable weight/cost savings) but it's a PITA to install and requires critical attention to terminating, physical support/protection, and protection from corrosion that will be beyond the capabilities of most here. Copper is much easier to install.

    As for any differences between fine and coarse stranded wire, given the same material and total cross-sectional area of the conductor as measured by it's AWG size, any difference in current-carrying capability will be too small to measure outside of a lab unless the wire run is measured in thousands of feet. Finer-stranded wire is easier to install but more expensive to make. But fine-strand wire does have one little-known advantage over it's coarser brother. Under extremely high transient currents, it won't 'thrash' as much. If you've ever seen a high voltage line dropped to the ground, it will thrash just like an uncontrolled high-pressure water or air hose. The more you increase the strand count, the less 'thrashing' you'll get. The finer strands can't develop as much 'leverage'.
     
  28. 1971BB427
    Joined: Mar 6, 2010
    Posts: 7,052

    1971BB427
    Member
    from Oregon

    I always use the frame, even on Unibody cars. But I run a full size ground from battery neg. to frame in the rear, and another full size cable from frame at the front to engine block. I bare every connection front and rear, and also run a ground strap from frame to body at either one or the other end.
     
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  29. AZbent
    Joined: Nov 26, 2011
    Posts: 272

    AZbent
    Member

    Using the frame, as a return to the battery, is very acceptable. Airplanes have been this way since the beginning. You need your ground wire to be the same size as your power wire. As been said before, your ground connection needs to be clean and tight.
     
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