Truck charge camper battery?

[Manfred]

I tried a search on this but I didn't come up with anything, maybe wrong search words 🙂 Anyway, for the past couple of years my fridge protocol has been to plug into shore power the night before we leave to get the fridge to the proper temp and pack food. The next morning before we leave I switch the fridge to DC power; when we get to the destination I switch the fridge to propane. My question: will the truck battery keep an adequate charge on the campers battery while the fridge is running? My thought has been conserve the propane and let the trucks alternator charge battery/run fridge. I have a 100W solar panel - 2005 Northstar camper with dual batteries - 2016 f250. Thanks

[Manfred]

Manfred wrote:
I just installed a new solar panel controller that gives more information about the camper battery status. I'm going on a road trip in a couple of days and will pay attention to the camper battery draw when running the fridge on DC while driving.

PS - thanks for the heads-up about changing my signature; it still shows my old Lance. 🙂

Just a follow-up post regarding my road trip - with shore power to the camper battery charge was 14.4V - switched the fridge to DC power and drove for 5 hours which included a 1 hour stop, sunny day - after 5 hours battery was at 12.8V. Seems like an acceptable drop in voltage. Perhaps this winter I'll replace the wire from the solar panel to the batteries - 14 gauge to 12 or 10 gauge.

[Kayteg1]

I check my camper for using truck inverter and my fuse box is under the small window that makes passage to the truck. So all I need is disconnect fridge wire at the breaker, extend it with cable that will reach my truck plug (6-8') and plug it into truck when driving, or into the camper outlet when on shore power.
PROBLEM SOLVED and my fridge will perform at 100% not at lower output with 12V.

[Grit_dog]

HMS Beagle wrote:
I'd try to fix the fridge. It should work fine on Propane. If you have two 20 lb tanks (most common) cooking and running the fridge you can live in it for at least a couple of months without having to fill. The furnace uses lots of propane - the fridge and cooking very little.

Nothing wrong with improving the charge circuit either. Even though the Lance may have #8, the truck is unlikely to - they are usually #1 or smaller.

Agree run it on propane and save the hassle.
However, having a truck with dual batteries and a monster alternator, I'd totally run a dedicated charging circuit if I traveled with the camper a lot.
BTW, you got your wire sizes backwards. Larger number = smaller gauge wire.

[Manfred]

full_mosey wrote:

Manfred wrote:
...
In the end it may boil down to just run the fridge on propane while driving although I like the idea of using free energy to power the fridge.
...

FREE? Nope, your alternator does not run for free.

HTH;
John

Yeah, I figure I'm going camping regardless if I have a fridg to keep powered up - if I have the alternator and solar panel to produce some energy while I'm driving to my destination, that's icing on the cake. 🙂

[Kayteg1]

Running alternator does not cost you the hassle of disconnecting the cylinders, carry them to fill station and wait to pay for propane.
Running on electricity is not for money saving, but for safety and convenience.

[full_mosey]

Manfred wrote:
...
In the end it may boil down to just run the fridge on propane while driving although I like the idea of using free energy to power the fridge.
...

FREE? Nope, your alternator does not run for free.

HTH;
John

[Kayteg1]

Using the calculator linked by Powerdude, even #6 cable will give you 0.7 V drop when you run it via bumper plug, what gives about 30 feet of wires before they reach the camper fridge.
I have another idea. My Ford has build-in 400W inverter and it is a good one as I tested it to run my small air compressor out of it.
So instead of tearing the truck and camper apart to run #2 cables - how about running #14 extension cord from truck 120V plug to refrigerator?
That would also run more powerful 120V fridge element.
I drive with rear window open and inner tube sealing the gap between truck and camper windows, so all I need is to find how to pull fridge plug up front and 8 feet of cheap extension cord will do.
The only trouble I see now is truck alarm going off when I park the truck with rear window open.

[Rubiranch]

Does a fridge really use that much propane to warrant the expense of 100-200 watt solar panels?

[HMS_Beagle]

I'd try to fix the fridge. It should work fine on Propane. If you have two 20 lb tanks (most common) cooking and running the fridge you can live in it for at least a couple of months without having to fill. The furnace uses lots of propane - the fridge and cooking very little.

Nothing wrong with improving the charge circuit either. Even though the Lance may have #8, the truck is unlikely to - they are usually #1 or smaller.

[work2much]

We run on 12v while driving and when the solar panels are in the sun while parked. That has worked well for us. That is with 500 watt solar panels and with 200 AH (425 AH total) of usable battery. With stock type battery and 100 watt solar you will run your batteries down, even while driving. You could run some larger wires between truck and camper batteries to increase the trucks ability to charge/power the 12v system of the camper.

[Manfred]

Thanks for the comments/suggestions/insights, it gives me a lot to contemplate. 🙂 I have used the camper about 4-5 times a year with an average of 4-5 hour drive to the destination. I just installed a new solar panel controller that gives more information about the camper battery status. I'm going on a road trip in a couple of days and will pay attention to the camper battery draw when running the fridge on DC while driving. In the end it may boil down to just run the fridge on propane while driving although I like the idea of using free energy to power the fridge.

PS - thanks for the heads-up about changing my signature; it still shows my old Lance. 🙂

[Camper_Jeff___K]

Your fridge on DC uses 15 or so amps?
Your alternator puts out 160 amps. Mine does.
Lots of extra power. Powering through the TC plug and 12 gauge truck wires will introduce a lot of I/R drop and loss of power to the fridge due to the small wire size.
In the Truck Camper University section, there are several good threads on how to install a 4 gauge wire from the truck alternator to the TC batteries and electrical making a marked improvement. It did for me. Enough so, I don't need a generator, I just run the truck for a while to charge the AGM batteries if the solar isn't keeping up.

[Powerdude]

You are right that as a percentage it is a major voltage drop.

I haven't measured at the alternator and at the camper battery. Most alternators in my experience put out 14.1 volts. The camper plug goes through my guess is at least 20 feet of wire outside the camper, and maybe 10 feet inside the camper because it's on the other side of the camper from the battery and the Lance plug.

30 feet of wire should produce about a half a volt drop at 12 volts, see calculator here Use 15 feet and 8 ga wire.

Important point, for 10 ga wire you will lose 0.9 volts, almost a full volt, using the same numbers.

But, using 8 ga wire it is good enough so that at least the battery drain does get offset somewhat by the alternator charging. And the battery does charge, just not fully.

At least it will prevent it from being drained to the point where its life would be significantly shortened.

[cewillis]

Powerdude wrote:

Measured voltage at the truck 12 v plug is 14.1 volts.

Measured voltage at the camper 12 v plug is 13.68 v.

Slight voltage drop of 0.42 volts.

Battery charges just fine while driving.

What about at the alternator and at the camper battery?
That is a major voltage drop, and you're not going to fully charge your battery at that voltage (for any deep cycle battery I've ever seen or heard about).