What gauge wire for truck to trailer charging?

[Buddha.]

My new to me ranger doesn't have a seven way RV style trailer plug. I have to run a wire from the battery to the new plug I'm installing but am unsure of the size. I hear talk about how the factory wiring doesn't do much to charge the trailer batteries. The kit I bought comes with 10 or 12 gauge (and a 30amp fuse), I was thinking 8 gauge to minimize voltage drop. Can I "re-pin" my pre wired seven way socket to take an 8 gauge or would I just connect to the exiting wire?

Yes I know I can run an extra pair of charge wires besides the seven way but since I'm starting fresh with the seven way I thought I'd start there.

 

[DiploStrat]

What distance, how many amps, target voltage i.e., what kind of battery, and, of course, are you using a battery-to-battery charger at the distant end? (Hint: Most of us would tell you to simply ignore the multi-pin for charging.)

Use this and have fun: https://www.calculator.net/voltage-...l&necpf=0.85&material=copper&wiresize=0.8152&resistance=1.2&resistanceunit=okm&voltage=12&phase=dc&noofconductor=1&distance=25&distanceunit=feet&amperes=50&x=61&y=11&ctype=size

 

[Rbertalotto]

Don’t even bother. Do yourself a huge favor and buy a Renogy Dc to Dc Charger. The price has come way down. The 20 amp version might be perfect for your Rangers alternator. This will charge your batteries properly without damaging your alternator and/or your battery in the trailer.

 

[john61ct]

Blue Sea Circuit Wizard is good too.

With a DCDC at the target battery you get a better handle on the amps drawn, and also deliver a good profile regardless if voltage drop, so you can use thinner cabling.

With LI chemistry the target bank really needs the DCDC very thirsty for too-high current

 

[john61ct]

Use an Anderson connector, forget trailer plugs for this

 

[DiploStrat]

But to repeat - a B2B can assure the proper voltage and, if needed, limit the amp flow, but it still requires adequate wiring. AFAIK, no multi-pin connector has adequately large wires.

 

[Alloy]

Don’t even bother. Do yourself a huge favor and buy a Renogy Dc to Dc Charger. The price has come way down. The 20 amp version might be perfect for your Rangers alternator. This will charge your batteries properly without damaging your alternator and/or your battery in the trailer.

???? this......it the best way to bring the voltage up high enough to the trailer battery for proper charging to take place.

 

[billiebob]

What distance, how many amps, target voltage i.e., what kind of battery, and, of course, are you using a battery-to-battery charger at the distant end? (Hint: Most of us would tell you to simply ignore the multi-pin for charging.)

Use this and have fun: https://www.calculator.net/voltage-...l&necpf=0.85&material=copper&wiresize=0.8152&resistance=1.2&resistanceunit=okm&voltage=12&phase=dc&noofconductor=1&distance=25&distanceunit=feet&amperes=50&x=61&y=11&ctype=size

Very good explanation tho I doubt many of us will use or understand the calculator. The theory is very well explained.

 

[Buddha.]

Alright, thanks for the replies.

The question still exists however. The truck needs a wire ran from the battery to the seven way. There is no wire currently there for the task. I can run any size I want to. What size would you use? I don’t mind spending more on wire if it works better.

I have the renogy 40 amp dc to dc unit floating around from a trailer I sold and I may add it in the future. The seven way will happen first.

 

[mep1811]

I ran a 10ga wire from my truck battery to an Anderson Powerpole plug in the rear. I have the same running into the Red Arc Manger 30 to charge the trailer battery . Works like a charm.

 

[86scotty]

I'd run 10 gauge.

 

[ns7i]

If you plan on using the 40A DC-DC charger you’re going to probably want 4 or 6 AWG depending on the length of the run.


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[Alloy]

10 GA if your running lead acid battery(s)

For Lithium then use a wire size calculator for 50amps (20% oversize for the 40A Renology) and include the neg wire in the harness.

You'll need 50A breakers to protect the wire. One at both ends since there's a power source at both ends.....not 3 like they did here.

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[DiploStrat]

Very good explanation tho I doubt many of us will use or understand the calculator. The theory is very well explained.

Actually, it is not hard. Let's play.

-- Guessing that the truck alternator runs at 13.9vf, call it 14v.

-- Assuming a normal truck, with batteries at the front, pace it off. For giggles, let's call it 30 feet from the front of the truck to the front of a trailer.

-- If we are going to use a B2B, or the Manager 30, let's call the charger 30A. You need to allow about 10% for losses, so let's give the desired amps as 35A.

-- Allowing the B2B to boost the voltage for lead acid, and manage the amps for lithium, let's try to limit the voltage drop to 5%, so call it 13.5v at the B2B.

That gets us this: https://www.calculator.net/voltage-...anceunit=feet&amperes=35&x=72&y=13&ctype=size

So you want about 4 AWG, unless I missed a step. (Always possible!) Probably would not see any real-world difference dropping to 6 AWG.

 

[john61ct]

The truck needs a wire ran from the battery to the seven way. There is no wire currently there for the task. I can run any size I want to. What size would you use? I don’t mind spending more on wire if it works better.

I have the renogy 40 amp dc to dc unit floating around from a trailer I sold and I may add it in the future. The seven way will happen first.

DO NOT USE THE SEVEN WAY.

It simply does not allow those amps to flow safely. Dangerous, fire risk, too much resistance.

Also wasting the energy heating up, functionally a bottleneck.

And the battery will very likely get murdered from PSOC abuse.

If you're not going to do it properly then you need to get deeper in the weeds.

What is the type, lead or LI?

When at 50% SoC, how many amps does it pull from your alt at high RPM with a short run?