8 Gauge Wire

If you are 25’ from battery to charger isn’t the run actually 50’ there and back ?

otrfun wrote:

LaneW wrote:
. . . I think I need to run a 4awg . . .

What is the max *input* current rating for your dc to dc charger? This input current rating and the length of the cable run would determine which gauge cable is most appropriate for the input. You may find this voltage drop calculator helpful. IMO, a voltage drop of <2% is ideal, but up to 3% is acceptable.

We ran approx. 25 ft of 2 gauge cable from the engine compartment to the input of our dc to dc charger inside our truck camper. Our dc to dc charger is rated for 40a of *output* charge current. The *input* current (i.e., alternator load) will always be higher.

The 25 ft of 2 gauge cable nets us a ~3% voltage drop at 44-45a (nominal alternator load when producing 40a of output charge current). Yes, we could have used 25 ft of 4 gauge, but that would have increased voltage drop, reduced system efficiency, resulting in a higher load on the alternator. If we had used 4 gauge, the alternator load would have increased to approx. 50-55a (or almost 60a using 6 gauge) while still producing the same 40a of output charge current. If you're interested, Ohm's Law describes all these relationships in more detail.

If you're not concerned about the load (i.e., wear and tear) on the alternator, then using a smaller cable is fine. If you are concerned about reducing the load on the alternator, then using a larger cable is the way to go. Your choice.

Well, of course I am concerned about wear and tear on my alternator……..

What I am looking at installing is DCC30S 12V 30A Dual Input DC-DC On-Board Battery Charger with MPPT. I am looking at the specs but not finding the input current. I am still looking for that. But, and I’m sure I dont understand as well as you, I will be at a bit under 25 ft from truck batt to charger, which based on the specs I see online would be on the long end fog 6 awg, or safe with 4 awg. Right?

LaneW wrote:
. . . I think I need to run a 4awg . . .

What is the max *input* current rating for your dc to dc charger? This input current rating and the length of the cable run would determine which gauge cable is most appropriate for the input. You may find this voltage drop calculator helpful. IMO, a voltage drop of <2% is ideal, but up to 3% is acceptable.

We ran approx. 25 ft of 2 gauge cable from the engine compartment to the input of our dc to dc charger inside our truck camper. Our dc to dc charger is rated for 40a of *output* charge current. The *input* current (i.e., alternator load) will always be higher.

The 25 ft of 2 gauge cable nets us a ~3% voltage drop at 44-45a (nominal alternator load when producing 40a of output charge current). Yes, we could have used 25 ft of 4 gauge, but that would have increased voltage drop, reduced system efficiency, resulting in a higher load on the alternator. If we had used 4 gauge, the alternator load would have increased to approx. 50-55a (or almost 60a using 6 gauge) while still producing the same 40a of output charge current. If you're interested, Ohm's Law describes all these relationships in more detail.

If you're not concerned about the load (i.e., wear and tear) on the alternator, then using a smaller cable is fine. If you are concerned about reducing the load on the alternator, then using a larger cable is the way to go. Your choice.

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It’s all 4ga wire.

Srschang. This is really helpful. I like that battery post mounted fuse. And the “gland” that you describe going through the front of you camper. That’s really nice - where do I find one of those? And is that 4 awg where on the plug? It looks smaller in the pic.

Thanks!

On the driver side battery in my Ram, there's a High Amperage Power Point (HAPP) that I installed a 60A fuse. The HAPP is just a threaded post that you can draw up to 300 amps from. I ran 4 gauge wire under the cab of the truck, through a plastic hole cover in the front of the bed, to the Pollak outlet mounted in the board that keeps the camper from hitting the top bed rail. The plug end of the Pollak connector is connected to 4 gauge wire that goes through a sealed gland into a Victron 12-12 30 amp converter inside the camper. 4 gauge wire runs from the Victron to the power center of the camper. Then 4 gauge wire runs from the power center to the 2 100 ah lithium batteries.

srschang wrote:
That NAPA plug looks exactly like the Pollak plug I used on my charging cable from my truck batteries to the DC-DC charger in the camper.

Pollak Outlet

Pollak Plug

Can you tell me more about how you wired it? Same thing Im trying to do. Routing of cables, sizing, connection location, etc….

That NAPA plug looks exactly like the Pollak plug I used on my charging cable from my truck batteries to the DC-DC charger in the camper.

Pollak Outlet

Pollak Plug

Napa has a 100 amp 2 wire Lift Gate Plug set you can use to add a heavy gauge umbilical between you camper and your truck.

https://www.napaonline.com/en/p/PHI15326 - Outlet
https://www.napaonline.com/en/p/PHI15336 - Male Plug

NRALIFR wrote:
Brad, if your goal is to get good refrigerator performance in DC mode and still keep the camper batteries fully charged, you might want to read this topic of mine in Tech Issues. I did this after being disappointed with the camper battery charging I was seeing after running 4 AWG welding cables from the truck batteries to the camper plug in the bed of the truck. My camper is also a Lance, so the wire size then changed to 8 AWG in the umbilical.

When I had a 1995 F350, I upgraded the truck-side wires to 6 AWG, connected them directly to the alternator, and got acceptable charging performance to the camper battery. On my 2010 F450, I went to 4 AWG wires still connected directly to the alternator, and was surprised to see that the charging performance was no better than the old truck. Possibly because the camper umbilical wires were still 8 AWG, but upgrading them was going to be a huge project as you can see in the linked Tech Issues topic.

When I upgraded the charge wires on my current truck, I found that the alternator/battery charging system on the truck had changed so radically that I was very apprehensive about connecting any auxiliary loads directly to the alternator. Plus, if you have a single alternator on your truck, it’s located way down low on the driver-side of the engine, and you’d have to remove a lot of stuff to get to it. I connected my new charge wires directly to both truck batteries, which improved the charging performance over the OEM wires, but it still wasn’t as good as what I was seeing out of the older trucks. It wasn’t keeping up with the drain on the camper battery from the fridge running in AC mode through an inverter, or running in DC mode.

Without going into a long-winded explanation, the fact is the charging systems on new vehicles is so tightly controlled by the ECM that it’s nearly impossible to get decent auxiliary battery charging out of a single alternator system. I’m fairly certain that on a new truck with a single alternator, you could run 0000 cables to the camper and still not get good performance. I have no idea if the dual alternator systems work any better since I don’t have dual alternators.

I finally bit the bullet and did what I describe in the linked topic, including upgrading the camper umbilical wires to 4 AWG as well. That required removing the water heater from the camper so I could get to the area the wires enter the camper. The results have been fantastic. The refrigerator DC mode now works so much better that I no longer run the fridge in AC mode through an inverter. I believe this is due to the camper voltage always being over 14 volts thanks to the Redarc DC-DC charger. Best of all, we always arrive at camp with a fully charged camper battery.

***Link Removed***

:):)

I know this is a very old post, but I am trying to do something similar on my 2022 Lance 825. Adding a Renogy combination DC-DC/MPPT charger and 200 ah lithium. I think I need to run a 4awg from my truck battery (2016 F350) to the go where the ACR is now in the camper and cant figure out how/where to get the wire into the camper and routed to the right place. Currently the Lance plug and cable has only an 8 awg incoming, but somewhere it changes to a 4 awg inside, because I see a 4 awg connected to the battery side of the ACR. Any help?