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DG N. AL · 07-27-2019, 07:36 PM

We have a 2018 Cedar Creek 36CK2 with a Samsung residential refrigerator. The trailer came with 2 Interstate deep cycle batteries. Our problem has been that driving a 12-13 hour day would just about discharge the batteries. If we did the "park at Walmart", we would run the generator for a couple of hours before going to bed to recharge the batteries. We would run the generator the next morning until we were back on the road (maybe an hour). By lunch on the next day, the batteries would be dead. Our truck wiring has the hot wire in the trailer plug, but the gauge of the wire was too small to keep the batteries charged.

I considered adding solar to the trailer to charge the batteries in route, but that looked expensive and possibly unreliable. I decided to upgrade the wiring between the truck and trailer to charge the batteries. I ran 2 gauge wire (hot and ground) from the truck batteries to the trailer batteries. I put heavy fuses (i forget the amperage) at the truck and trailer batteries. I used 175 Amp quick connectors to make the connection at the trailer. I put a continuous duty solenoid in the hotwire on the truck so that the wire is only hot when the truck key is on. This is to keep the trailer from draining the truck batteries when the truck is not running. I wired the solenoid thru one of the upfitter switches on the F250 so that I can manually cut the solenoid off. This allows me to manually turn the power off when the trailer is not connected. Just to be on the safe side and give more reserve, I added two more batteries to the trailer giving a total of 4-12 volt batteries. When they need replacing, I may consider using 4-6 volt golf cart batteries.

We just completed a 1600 mile round trip and the batteries on the trailer stayed fully charged. I think this will solve the charging problems of the trailer batteries while towing the trailer. I watched the alternator gauge on the truck this trip and it never left the normal range.

twinboat · 07-27-2019, 08:27 PM

Great job.
You built a battery isolation/charging system something like most MHs have.

A solenoid connects the chassis batteries to the house batteries with heavy cables when a charging voltage is available.

mobilemike · 07-28-2019, 10:02 AM

Good job. That is similar to what I have done. I just swapped a constant duty solenoid for a voltage sensing relay.

I am not sure why this is a new thing for 5ers. Boats have been charging "house" battery banks from the drive engines for decades.

masterdrago · 07-28-2019, 04:07 PM

It would be interesting to me to know more about your installation. Fuses? What type wire? How run? Encased in what? How connected at the battery (s), etc. How run through the 5r hitch? Anything else you might recommend in the installation?

DG N. AL · 07-29-2019, 07:20 PM

Quote:

Originally Posted by masterdrago

It would be interesting to me to know more about your installation. Fuses? What type wire? How run? Encased in what? How connected at the battery (s), etc. How run through the 5r hitch? Anything else you might recommend in the installation?

I used this for the wire. I terminated the wire with these lugs. I used the type of fuse pictured below. I put a fuse at both the truck battery and the trailer battery. I put heat shrink on the fuses and all of the lugs.

I ran the cables down the left frame rail. There was a major wiring harness on that rail and I zip-tied the cable to it. You could run the cable in a corrugated loom if you desired. I put my plug above the trailer connection in the bed of the truck (see pictures). I mounted the solenoid on the firewall of the truck. My truck is a 2012 Ford F250.

On the trailer, I used an electrical fish tape to pull my cable from the pin box to the front compartment. I was able to run the fish tape right beside the trailer light cable. My batteries and inverter are in the left corner of the front compartment.

masterdrago · 07-31-2019, 09:21 PM

Quote:

Originally Posted by DG N. AL

I used this for the wire. I terminated the wire with these lugs. I used the type of fuse pictured below. I put a fuse at both the truck battery and the trailer battery. I put heat shrink on the fuses and all of the lugs.

I ran the cables down the left frame rail. There was a major wiring harness on that rail and I zip-tied the cable to it. You could run the cable in a corrugated loom if you desired. I put my plug above the trailer connection in the bed of the truck (see pictures). I mounted the solenoid on the firewall of the truck. My truck is a 2012 Ford F250.

On the trailer, I used an electrical fish tape to pull my cable from the pin box to the front compartment. I was able to run the fish tape right beside the trailer light cable. My batteries and inverter are in the left corner of the front compartment.

Much thanks for the details. I was looking to do a project like this but needed some guidelines.

Gray01 · 08-04-2019, 12:23 AM

Excellent post, with very helpful detail!

I have thought about doing this but always wondered about how to bring it all together.

I really like the concept of using the upfitter switch for positive control.

Did you “marry” the charge line (wire ties, etc) to the trailer connection cord?

How did you connect to your trailer batteries?

DG N. AL · 08-04-2019, 02:02 PM

Quote:

Originally Posted by Gray01

Excellent post, with very helpful detail!

I have thought about doing this but always wondered about how to bring it all together.

I really like the concept of using the upfitter switch for positive control.

Did you “marry” the charge line (wire ties, etc) to the trailer connection cord?

How did you connect to your trailer batteries?

I did not "marry" the charge lines with the trailer cord, but I don't see a problem to do so. In fact it is probably a good idea. I made the connection to the trailer batteries in the same manner as the truck except that I connected the positive on one end of the parallel run and the negative on the other end. I do all my trailer battery connection that way. The theory is that it should promote equal charge and drain on all four trailer batteries. I hope that makes sense.

Gray01 · 08-04-2019, 02:17 PM

Quote:

Originally Posted by DG N. AL

I connected the positive on one end of the parallel run and the negative on the other end...I hope that makes sense.

Yes, I understand that explanation.

Your layout makes it much easier for me to create a plan of attack.

rebby · 08-09-2019, 08:56 AM

DG N. AL,
Excellent write up here. I've been researching a project such as this for a couple of weeks now (moving to a res fridge in the new trailer) and this is one of the most complete references that I've been able to find. I take delivery of the new trailer next week so I just started getting things wired on the truck side. For the most part our systems are similar so I'll just bullet list my configuration (for now, I can add a few pics when I get it all installed).

For the solenoid I went with a Stinger SGP38 80-amp isolator. This is essentially the same thing that you're using, I just had a spare in the garage so I'm going to run with it. I like that it has both a hot trigger and a ground trigger (like a "normal" relay, instead of getting ground from the mount). I'll wire the hot side of the trigger to an ignition hot source and wire the ground into a switch that I have in the cab. This will allow me to quickly and easily shut everything down should the need arise (you could just as easily run the hot wire through the switch too, I just prefer to switch low amp grounded feeds when possible).

I added a digital multimeter to help monitor the charge output. It's inexpensive and I'll be able to tell at a glance how things are working.

Rather than run directly off the battery and depend on the voltage regular in my truck, I'm isolating the batteries in the 5th wheel with a DC to DC Battery Charger. I ordered the 40a unit for my application. I'm hoping that having this charger in the system will provide for a better charge for the camper batteries than I'd get going direct off the truck.

Anyway, thanks again for sharing. It's nice to know that I'm on the right track.

mobilemike · 08-09-2019, 09:53 AM

The DC to DC charger is a great addition. It solves several problems.

Voltage drop during charging.

Voltage drop to voltage controller in the truck 25ft away.

Manages charging to large battery bank size differences between the truck battery and the house batteries.

SafeDave · 07-21-2020, 07:51 AM

With the setup mentioned and the 40AMP DC to DC charger, how big of an inverter can you power with 4 T105 batteries? Thanks

PulNSerenity · 07-22-2020, 05:39 AM

Quote:

Originally Posted by Gray01

Excellent post, with very helpful detail!

I have thought about doing this but always wondered about how to bring it all together.

I really like the concept of using the upfitter switch for positive control.

Did you “marry” the charge line (wire ties, etc) to the trailer connection cord?

How did you connect to your trailer batteries?

He just needs to do the whole project over again, record it, & post it on youtube!

It is a great post! I may do something like this down the road.

grindstone01 · 07-22-2020, 06:30 AM

To the OP, that power usage does not seem right. I have a Haire 10.3 resident frig and recently had a different experience during a 300 mile drive on a 90F day. When I started, my single RV 12V battery was not fully charged, only read 12V on the meter. When I arrived to the new cg, my truck had charged the battery to 12.7V and the refrig had been running and we arrived at it's normal 39F inside temp.
I did end up getting a new RV battery, since the old one would not hold a charge. My truck does have a 2 battery system.