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New FWC's have 10awg wire internally, why have a thicker wire from truck?


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#1 kmcintyre

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Posted 25 October 2021 - 06:11 PM

I was inquiring about running a 6awg wire from the truck battery to my (someday) new hawk flatbed and asked what they do at the factory.

 

They replied that the internal wiring inside the camper is 10awg; which they use from the truck battery to the camper. 

 

If that's true, the only benefit I can see is that there might be a slight voltage drop from the truck battery to the camper but after that, it won't matter.

 

Calculations for a 15' run @ 6awg, 10amps is a .4V loss.

Calculations for a 15' run @ 10awg, 10amps is a .98V loss.

 

So, you lose about .5V using 10awg.

 

Since I don't know how they do the connections on a Flatbed (or how they do it now vs. my 2001) I imagine that the wire comes into the flatbed and into a fuse box where it splits off to the house battery and electrical components in the camper?  If that's the case, you could upgrad the wiring to where the fuse box is and then upgrade the wiring to the battery.

 

I'm leaving off the DC-to-DC charger, etc. for ease in this discussion.

 

 

Kevin


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#2 PaulT

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Posted 25 October 2021 - 07:41 PM

The primary benefit of the larger wiring from the truck to the batteries is that the voltage drop is less allowing the batteries to be charged more completely and in a shorter time. Voltage drop from the batteries to the lights or appliances that use 12 volt power is not as critical and 10 AWG is likely fine. The half volt difference between the two wire gauges can make a significant difference in charging the batteries.

 

Paul


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#3 pvstoy

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Posted 25 October 2021 - 08:00 PM

Did you include both negative and positive wire runs in the loss? Times a one way wire run by 2.

I remember reading that charging straight from alternator wire loss makes a difference to the camper battery. Add a DC to DC charger then 10 gauge may not be a issue, but some have had problems with factory 10 gauge cycling on and off the DC to DC charger due to the loss in wire size and length.
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#4 Beach

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Posted 25 October 2021 - 10:36 PM

Might affect the bulk charge on some batteries. If your battery requires 14+ volts(as many do for bulk charge) and your output from the alt is 14 or so volts, then you drop approx. 1 volt on the way to the battery, you will not get a proper charge.


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#5 kmcintyre

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Posted 26 October 2021 - 01:45 AM

The primary benefit of the larger wiring from the truck to the batteries is that the voltage drop is less allowing the batteries to be charged more completely and in a shorter time. Voltage drop from the batteries to the lights or appliances that use 12 volt power is not as critical and 10 AWG is likely fine. The half volt difference between the two wire gauges can make a significant difference in charging the batteries.

 

Paul

 

The only thing is they run 10 awg from the truck battery to the camper and then the camper has all 10awg.  Doesn't matter in this scenario other than making sure that you get less voltage drop from the truck to the camper (at least that's what I'm thinking).


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#6 kmcintyre

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Posted 26 October 2021 - 01:46 AM

Might affect the bulk charge on some batteries. If your battery requires 14+ volts(as many do for bulk charge) and your output from the alt is 14 or so volts, then you drop approx. 1 volt on the way to the battery, you will not get a proper charge.

 

I wonder how many people have the standard 10awg wiring then...  


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#7 kmcintyre

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Posted 26 October 2021 - 01:47 AM

Did you include both negative and positive wire runs in the loss? Times a one way wire run by 2.

I remember reading that charging straight from alternator wire loss makes a difference to the camper battery. Add a DC to DC charger then 10 gauge may not be a issue, but some have had problems with factory 10 gauge cycling on and off the DC to DC charger due to the loss in wire size and length.

 

I have a DC-to-DC charger for my LifePO4's!


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#8 Vic Harder

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Posted 26 October 2021 - 02:43 AM

Think of it this way:  From the DC fuse box, the wiring FWC/ATC/Others use is NOT 10AWG, it is 14 or even smaller.  But, to the distribution panel/fuse box, they all see the wisdom in using a fatter wire.  And that is for a run 10'  long or less from the camper battery to the dc fuse panel.

 

With smart alternators, and differing battery chemistries, we definitely want to minimize the voltage drop from the truck to the camper.  


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#9 Wallowa

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Posted 28 October 2021 - 01:50 AM



I have a DC-to-DC charger for my LifePO4's!

 

 

My Orion DC/DC was wired with 4awg...Tundra/Hawk [side dinette] battery box right front corner of Hawk floor tub...not sure if that was what you were asking about but you mentioned DC/DC.


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#10 Jon R

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Posted 28 October 2021 - 02:52 AM

I wired mine with 6 awg Ancor marine wire from the truck battery to the Orion 12/12-30 and it works fine. The voltage drop at 30 amps is small enough that the Orion’s engine running verification test cycling is not triggered. My wire run is about as long as anyone would have for a truck camper installation. My truck is a crew cab long bed and the battery compartment with charger is at the very back of the camper.
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