Battery Cable Sizing

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Battery Cable Sizing

kramttocs
I see the page for cable lengths but was wondering if there was a chart for the recommended sizes for battery cables.

Have looked around and there is a battery cable site that lists recommendations based on the engine type but was curious what everyone here thought.

Not necessarily looking for stock sizes but more so the best size.

Here are the cables I can think of I am needing (will be custom making them) but please add any I've forgotten.

Positive battery to relay
Positive relay to starter solenoid (Pmgr)
Relay output to starter solenoid (trigger)
Negative to engine block


Aux battery:
Positive battery to isolator
Isolator to main battery
Negative battery to fender

Engine: 460

Going off memory regarding the isolator - there was originally a junction bolt there that I am replacing with the isolator but I can't recall the hot wire size and if it will be big enough. Additionally I don't recall if it has an inline fuse that will be needed.

Also, if any of these requirements change for different engine types, please add those as well.
Scott
Daily driver: 'Camano' 1986 F250 Supercab XLT Lariat 460/C6
Work truck: 'Chanute' 1980 F350 C&C 400/T18 - Gin Pole
Various parts trucks
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Re: Battery Cable Sizing

Gary Lewis
Administrator
Scott - Good questions.  Was just wondering that yesterday as I took off the ground cable on Big Blue and thought "That's not very big."  And if I have to move the aux battery to the passenger's side I'll have to have new cables.

How are you going to make them?  I have a 16 ton hydraulic crimper and it works great if you feed it the good Magnalugs.  I made all new battery cables for both batteries on our boat and used 2-0 marine cable.  They came out great, and I might consider using that size for my cables.

On the isolator for the aux battery, that circuitry is best shown in the 1985 EVTM on the Charge & Power Distribution - Gas Engine pages.  There's even a depiction of the stud you talked about as well as the relay.  But there's no true fuse, just a fusible link.

On the grounds, don't forget the one from the engine to the firewall.  And while you are at it, you might add grounds from the fenders to the radiator support and from the cab to the fenders.  I think Ford did that in later years, but Jim or Bill might tell us different.
Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker in front & 10.25 Spicer/Trutrac in back, & EEC-V MAF/SEFI

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Re: Battery Cable Sizing

kramttocs
Haha good. Glad to know I am not alone.

I've actually read your thread on FTE for your boat cables a few times and my 16 ton eBay crimper came today  
From that thread I've been tracking down magnalugs and am happy to see 45 and 90 degree options.

I have been leaning towards 1/0 for everything large (positive and negative) but mainly because a lot of those 'multi' battery post connectors seem to max out at that size and I was thinking they would make clean wiring for the aux battery and amp connections.

I was actually going to keep the factory wiring for the engine to ground but good call on the fender to rad support.
Also planning to directly ground the starter back to the engine ground post.

I'll check out that diagram for the aux.

Scott
Daily driver: 'Camano' 1986 F250 Supercab XLT Lariat 460/C6
Work truck: 'Chanute' 1980 F350 C&C 400/T18 - Gin Pole
Various parts trucks
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Re: Battery Cable Sizing

kramttocs
Looks like they used the same factory hot wire for both the lug and aux battery isolator. So I guess that guage is enough? I was thinking I'd need to run a full size battery cable across the firewall.
Scott
Daily driver: 'Camano' 1986 F250 Supercab XLT Lariat 460/C6
Work truck: 'Chanute' 1980 F350 C&C 400/T18 - Gin Pole
Various parts trucks
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Re: Battery Cable Sizing

ArdWrknTrk
Administrator
In reply to this post by Gary Lewis
It's odd that your block-frame-battery ground cable is undersized, Gary.

It's a circuit, and electrons have to flow all the way around the loop.

While the starter is probably the largest draw of most vehicles, it is only used intermittently, so even a heavy draw won't cause the cable to overheat (if it is properly sized for the amperage) something like a winch is much more taxing.

IMO, there's no such thing as to large or too many grounds.
When I did my 3G swap Ryan's kit included 2/0 cable to make up the links between alt -fuse and fuse-battery, so I picked up a 2/0 ground at the truck supply.
Intended for electric/hydraulic plow trucks that are always blasting the heater and have (had!) lots of auxiliary incandescent lighting.

1/0 seems more than ample for most any purpose.

My bricknose had braided straps, both firewall to intake and cab sill pinch weld to cab mount frame 'ear' beneath the drivers feet, circumventing the rubber isolators.

Maybe I can get a pic in daylight.
Still getting this new temporary phone to where I like it....
 Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with an Edelbrock 1826 and Performer intake.
Too much other stuff to mention.
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Re: Battery Cable Sizing

85lebaront2
Administrator
One of the improvements Ford did on the Aeronose trucks was the battery cables now run to the starter directly (PMGR starter) and the old starter relay is still there, but operates a much smaller wire to the starter solenoid. The body ground is now a pigtail (GM style) from the battery terminal end to the right inner fender. This is a picture of a friend's 1994 F150 battery and relay connections, the positive (inboard) cable has two branches, one to the starter, the other to the relay and remainder of the power, the alternator is connected there. My 160 amp 3G has a 200 amp megafuse in a holder next to the relay.
Bill Profile

"Getting old is inevitable, growing up is optional" Darth Vader 1986 F-350 460 converted to MAF/SEFI, E4OD 12X3 1/2 rear brakes, traction loc 3:55 gear, 160 amp 3G alternator Wife's 2011 Flex Limited Daily Driver 1994 Taurus LX Project car 1986 Chrysler LeBaron convertible 2.2L Turbo II, modified A413

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Re: Battery Cable Sizing

Steve83
Banned User
This post was updated on .
In reply to this post by kramttocs
kramttocs wrote
...a chart for the recommended sizes for battery cables.
4ga for all gas engines.
kramttocs wrote
...based on the engine type...
Some diesels draw more current due to their higher compression and heavier starters, but most stock-type gas truck engines' starters draw ~140A max, and require about the same-size cables.  Only a remote-mounted battery would necessitate an increase of 1 size (2 gauges lower).
kramttocs wrote
Not necessarily looking for stock sizes but more so the best size.
Stock is generally best.  Ford engineers know more about designing vehicles than anyone, and they know the company has to warrant their designs, so they design for high reliability.
kramttocs wrote
Relay output to starter solenoid (trigger)
That only has to power the solenoid, so its a MUCH-smaller wire than the battery cables.

kramttocs wrote
Isolator to main battery
That depends on what you plan to do with the aux.batt.  Ford only intended it to extend the key-off time (reserve minutes).

kramttocs wrote
Negative battery to fender
Bad idea.  The fender isn't well-grounded through its (painted) mounting points.  Either ground the battery to the frame, block, or firewall; or (better) just run its negative cable directly to the main battery negative (with as few bolted connections as possible).
kramttocs wrote
Additionally I don't recall if it has an inline fuse that will be needed.
Again: depends on your plans.  But generally: battery cables are too big to protect.  They need to carry all the current available, so fusing it would just cut power when you need it most.  This caption explains in more detail:

ArdWrknTrk wrote
IMO, there's no such thing as to large...grounds.
Although they're popular, big wires don't actually compensate for poor connections or poor circuit design.  They can actually hurt, due to being harder to manipulate, bend, and create good connections.  Their stiffness may distort the metal they're bolted to, causing a worse connection than with a properly-sized wire.  They're also exponentially more-expensive, without any corresponding benefit, over the appropriate size wire with good terminals.
ArdWrknTrk wrote
IMO, there's no such thing as...too many grounds.
If they're all large enough to handle the total current that might ever pass through all of them, then you're right.  But often, some of the "ground" wires are substantially smaller.  So if a big one is removed, or loses connection for any reason, the smaller ones might catch fire due to suddenly being subjected to all the current that the big one WAS carrying.  That's why automakers generally DON'T run parallel grounds.  If the ground circuit goes bad in one spot, it just shuts down all the circuits it serves - that's safer than setting fire to a smaller parallel wire.
ArdWrknTrk wrote
My bricknose had braided straps, both firewall to intake and cab sill pinch weld to cab mount frame 'ear' beneath the drivers feet, circumventing the rubber isolators.
Those are only for RFI - not for power grounding.  No measurable current should ever pass through them - only transient "noise".

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Re: Battery Cable Sizing

kramttocs


Thanks Steve.

4ga is good to have as a reference. I am actually starting to lean towards 1ga just because the crimper doesn't appear to have one for 1/0 and if 1ga is plenty...

I don't disagree on the Aux battery being grounded to the fender but that's how stock did it is the only reason I was considering it. I like grounding it to the main battery better.

For the relay to starter (trigger wire): 10ga? Or what is your numerical value of 'much smaller'?

My plan for the aux battery is to run my amp, sub, fog lights and eventually a run to the rear bumper for my trailer winch.

With those goals, the positive between the main and aux would just be for charging from the alt.
I assume the factory yellow wire would be enough for that?

Now lets say if I wanted to use the 'jumper' mode of the isolator. In that case I would need larger?
Scott
Daily driver: 'Camano' 1986 F250 Supercab XLT Lariat 460/C6
Work truck: 'Chanute' 1980 F350 C&C 400/T18 - Gin Pole
Various parts trucks
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Re: Battery Cable Sizing

ArdWrknTrk
Administrator
IIRC my PMGR starter was shown at 40A to pull and 13A to hold.
The instructions said to use 12Ga, and I believe I used 10.

I do think Gary has the chart, as I posted it back on FTE in response to his questions.
It shows all the parameters, such as draw at stall and the torque curve.
 Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with an Edelbrock 1826 and Performer intake.
Too much other stuff to mention.
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Re: Battery Cable Sizing

Steve83
Banned User
In reply to this post by kramttocs
kramttocs wrote
...the crimper...
Solder is MUCH better than crimping in this application, for several reasons.
kramttocs wrote
Or what is your numerical value of 'much smaller'?
I don't remember, but it's in the 1st diagram I posted above.  SMN is down for maintenance at the moment...
kramttocs wrote
My plan for the aux battery is to run my amp, sub, fog lights and eventually a run to the rear bumper for my trailer winch.
With those goals, the positive between the main and aux would just be for charging from the alt.
Not if you use ANY of those while the engine is running (alt. working).  In that case, the current to those loads could be expected to come from the aux.batt., the main batt., the alt., or any combination at any moment.  So the connecting wires between those 3 voltage sources should be sized for the peak load (probably the winch).
kramttocs wrote
I assume the factory yellow wire would be enough for that?
Only if you NEVER use a load larger than that Yellow wire can handle while the engine is running.
kramttocs wrote
Now lets say if I wanted to use the 'jumper' mode of the isolator. In that case I would need larger?
Yes, if you ever expect to pull substantial current INTO the aux.batt. or the circuits connected to it.
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Re: Battery Cable Sizing

85lebaront2
Administrator
Steve 83 - "Solder is MUCH better than crimping in this application, for several reasons."

If that is the case, then why don't the factories use soldered connections?

If you really want to see something interesting, un-wrap and remove all the goo from a Detroit factory multi-wire splice, it's welded.
Bill Profile

"Getting old is inevitable, growing up is optional" Darth Vader 1986 F-350 460 converted to MAF/SEFI, E4OD 12X3 1/2 rear brakes, traction loc 3:55 gear, 160 amp 3G alternator Wife's 2011 Flex Limited Daily Driver 1994 Taurus LX Project car 1986 Chrysler LeBaron convertible 2.2L Turbo II, modified A413

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Re: Battery Cable Sizing

kramttocs
If I want to add a 1/0 or 1 between the junction block or relay and the main battery, I can keep the factory hot yellow connected right?

The higher draw will take the larger cable, correct?
Scott
Daily driver: 'Camano' 1986 F250 Supercab XLT Lariat 460/C6
Work truck: 'Chanute' 1980 F350 C&C 400/T18 - Gin Pole
Various parts trucks
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Re: Battery Cable Sizing

Steve83
Banned User
In reply to this post by 85lebaront2
85lebaront2 wrote
...why don't the factories use soldered connections?
Because it's more expensive & difficult for mass-production than just melting the Lead into the battery cables.  But that's not as safe or practical for one person working on one vehicle as solder.
kramttocs wrote
If I want to add a 1/0 or 1 between the junction block or relay and the main battery, I can keep the factory hot yellow connected right?
Yes, as long as you make good splices, and NEVER disconnect the big one (even accidentally, as by a poor connection failing) while there's a heavy load on the aux.batt.
kramttocs wrote
The higher draw will take the larger cable, correct?
Not exactly; current will flow through both, based on the total resistance along each path between the points where you splice your new cable in.
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Re: Battery Cable Sizing

ArdWrknTrk
Administrator
In reply to this post by kramttocs
As the smaller wire -or cable- in parallel gets saturated (there are only so many free electrons to move) a greater percentage of current (amps) will be carried by the larger cable.

The yellow will be fine.

To Steve's statement.
I think Bill is referring specifically to harness splices wrapped in tape.

The older lead battery terminal lugs were done that way because battery cables are somewhat universal, and it's cheap, fast and easy to do that way in a production environment.

Harness splices are welded (fusion of the copper) because A) welding is stronger than solder. B) carries current better. C) there is no boundary for corrosion to get started.
 Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with an Edelbrock 1826 and Performer intake.
Too much other stuff to mention.
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Re: Battery Cable Sizing

TheScatch
This post was updated on .
In reply to this post by kramttocs
kramttocs wrote
My plan for the aux battery is to run my amp, sub, fog lights and eventually a run to the rear bumper for my trailer winch.
This is something I do not understand, this isn't the first time I have seen this. If your batter is set up where the main and spare battery share a positive and negative connection that battery is wired directly in parallel and at that point it makes no difference where you tap to power what.

What I would do is just tap off whatever location is convenient at that time and buy an appropriately sized fuse block, then use said fuse block to power whatever.

Looking at the diagrams below you can see that there is functionally no difference between these two methods, except putting in a fuse box is a cleaner install and will allow easier wiring and troubleshooting. Better to do the latter than have half a dozen wires hanging off the battery positive post.

Using the AUX battery


Using a fuse block


I have a lot of professional experience (16 years and 8 days) with wiring being put through the most abusive circumstances known to man. When done correctly a crimp is far superior to a solder joint. In my experience solder joints break over time with vibration and other outside forces. This is why outside of circuit boards solder joints are only used for shield splicing in aviation.
1986 F-150|Standard Cab|4x2|300Six|C6Transmission w/3.08 rear|Name:TBD
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Re: Battery Cable Sizing

ArdWrknTrk
Administrator
I'm interested in what you do for a living.

Electrician on oil rigs?
Mining?

What are the most abusive conditions known to man?
 Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with an Edelbrock 1826 and Performer intake.
Too much other stuff to mention.
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Re: Battery Cable Sizing

TheScatch
I have worked in aviation/aerospace both military and for a major company in the industry.

The wiring on those products goes through more vibration, intrinsic and extrinsic heat, rapid environmental changes, lightning strikes, corrosive fluid exposure (hydraulic, fuel, oil, coolants), and physical stress from flexing than any automotive or typical ground install. Sometimes all of the above at the same time, and they do it with crimps across the board. Splices, pins/contacts, shield terminations are all crimped in place.

We had a handful of soldered connections on the Harriers I worked on as a dual MOS 6312/6332 that would consistently fail, especially on antenna to the rear of the aircraft. Seen the same thing on helo's.

On the more modern examples of aerospace, pretty much outside of the printed circuit boards, solder has gone the way of the dodo. Hell the wires going to the power panels from the generators and engines are all copalum splices and crimps made with a hydraulic crimper that puts out a few thousand PSI. Actually I think pretty much every 1/0, 2/0, 3/0 cable is done in that manner. Smaller cables use smaller crimpers, and larger ones (10 gauge and up) use hand held hydraulic/ratchet type or powered hydraulic/ratchet type luggers. We call the hand held ones knuckle busters because when the crimp is finished the tension on the handles releases while your hulking out on it and you slam your knuckles together.
1986 F-150|Standard Cab|4x2|300Six|C6Transmission w/3.08 rear|Name:TBD
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Re: Battery Cable Sizing

kramttocs
In reply to this post by ArdWrknTrk
ArdWrknTrk wrote
As the smaller wire -or cable- in parallel gets saturated (there are only so many free electrons to move) a greater percentage of current (amps) will be carried by the larger cable.

The yellow will be fine.
Thanks!
Scott
Daily driver: 'Camano' 1986 F250 Supercab XLT Lariat 460/C6
Work truck: 'Chanute' 1980 F350 C&C 400/T18 - Gin Pole
Various parts trucks
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Re: Battery Cable Sizing

kramttocs
In reply to this post by TheScatch
TheScatch wrote
kramttocs wrote
My plan for the aux battery is to run my amp, sub, fog lights and eventually a run to the rear bumper for my trailer winch.
This is something I do not understand, this isn't the first time I have seen this. If your batter is set up where the main and spare battery share a positive and negative connection that battery is wired directly in parallel and at that point it makes no difference where you tap to power what.
It's the isolator that makes the difference in the diagrams and the reasoning. It allows the aux battery to be used without draining the main.
Scott
Daily driver: 'Camano' 1986 F250 Supercab XLT Lariat 460/C6
Work truck: 'Chanute' 1980 F350 C&C 400/T18 - Gin Pole
Various parts trucks
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Re: Battery Cable Sizing

Gary Lewis
Administrator
In reply to this post by TheScatch
TheScatch wrote
This is something I do not understand, this isn't the first time I have seen this. If your batter is set up where the main and spare battery share a positive and negative connection that battery is wired directly in parallel and at that point it makes no difference where you tap to power what.
The factory aux battery setup used a relay to parallel the batteries as soon as the key was turned on.  I think Scott is going to use a relay with electronics that senses battery voltages and won't parallel the two until one or the other gets to a preset value, showing it is getting charged.

So my guess is that he wants the sound system on the aux battery so he can drain it w/o fear of not being able to start the truck.  Which is why I put the winch on the aux battery on Big Blue.

As for the yellow wire, so far the factory wire has held on Big Blue.  But I've never done much winching w/o the truck running and therefor both batteries have been in parallel.  And I'm still running the 1G.  My worry about that wire is when the alternator has been replaced by a 3G and when the aux battery has been depleted and that big alternator kicks out twice what the original 1G was capable of.  
Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker in front & 10.25 Spicer/Trutrac in back, & EEC-V MAF/SEFI

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