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

[enblethen]

It is fairly easy to install a charge relay in most trucks.
Here is a good one. Note installation instructions.
Battery switch

[Kayteg1]

Suppose Ford is the only brand that has trailer charging wire run via ignition-activated relay.
Would expect other brands to follow on new models, but that might become knowledge-testing question for truck salesmen.

[PhilR]

My Chevy diesel charges the batteries in my Northern Lite camper when driving.... the electric switch (an option) in the camper must be in on position. When stopped with engine off, switch should be turned off so truck batteries won't be drawn down by camper. In my case, I have a solar panel which negates the problem. I have heard that some other truck brands do not work this way.....should be checked.

Phil

[Grit_dog]

Echo above comments. In general, no it won't without modifications to the wiring/charging circuit.
My camper charges like it should through the plug but it doesn't not keep up with the fridge on D.C.
Unless you want to modify for better results, just Run the fridge on propane all the time unless you have shore power. It cools better on propane too.

[Kayteg1]

mkirsch wrote:


2. An irrational fear of propane. The truth of the situation is that the conditions in the refrigerator compartment make it virtually impossible to have an explosion or even an out of control fire.

In my years of RVing I have seen too many RV burned down to the floor to not consider the risk.
Lower risk in TC, but lot of motorhomes have copper tubings carrying propane mounted on top of wheel wells.
Simple flat tire slapping the fender breaks the propane line, finding spark in such incident is not that hard and flat tire ends on totaled rig if not loss of human life.
Than ask gas station attendant how he feels about you fueling with flame-on, in the camper?

[Powerdude]

My propane side on my fridge doesn't work for ****, so I use DC power.

I have a Lance plug installed in the truck with the 8 ga wire running from the battery.

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.

[AnEv942]

?
Wondered when 'fear' would be thrown out there, which these posts about 12v always devolve to.
Or (per OP)
3. Conserve the propane

[mkirsch]

My guess is that this conversation was prompted by one of two things:

1. The refrigerator keeps blowing out. This is not normal and is a problem that can be addressed. Lots of discussion on this subject here.

2. An irrational fear of propane. The truth of the situation is that the conditions in the refrigerator compartment make it virtually impossible to have an explosion or even an out of control fire.

[AnEv942]

OP
Manfred you need to update your signature-appears many are responding to it and topic title and not reading post & question.

I'll further muddy the water,
I'm reading question is about powering refer between point A & B, on the road with 12v, starting with charged batteries.
Between solar and truck alternator, all it needs to do is supply at minimum what refer draws.
Biggest factor in using 12v on road IMO is never using without charge source (engine running). Turning on refer last, turning off first.
Its that draw down that system likely will have a hard time with-supply adequate charge while supplying ~16-19amps to refer.

[Kayteg1]

Start with reading refrigerator sticker.
The 12V element is rated for much less power than 120V element.
I post my test somewhere on this forum about my Dometic and 120V and gas had almost the same performance. Gas run like 2 degrees colder, but that could be within error margin.
Standard truck plugs are rated for 30 amp when big fridge is rated 18 amp.
Lance idea might be overkill, but usually weak point are the plugs. They are build cheaply and often neglected, so making bigger connection is never bad idea if you want to spend time on it.
Would I make new connection, I would make it >100 amp rated so I could use my dual truck batteries for fast inverter/microwave use on the road. That also would allow me to run fridge on 120V for full output.
For me, driving in 110-120F weather now the 12V is just not giving enough cooling power.

[bighatnohorse]

cewillis wrote:

bighatnohorse wrote:
Unlike other camper brands, your Lance camper has a factory supplied proprietary heavy duty power supply wire built into the umbilical cord to the truck.

What does 'proprietary heavy duty' mean here?

It means an 8 gauge wire. Lance documentation specifically calls out this wire for powering the refrigerator.
See: http://manuals.adventurerv.net/Lance-6-way-wiring-schematic.pdf

[cewillis]

bighatnohorse wrote:
Unlike other camper brands, your Lance camper has a factory supplied proprietary heavy duty power supply wire built into the umbilical cord to the truck.

What does 'proprietary heavy duty' mean here? Unless the wire is at least 4g (2g is better), the alternator output voltage is most likely reduced too much to ever fully charge the camper batteries.
The so-called 'isolator' also causes a voltage loss in some cases.

Both can be assessed by comparing output voltage at the alternator (14.2v - 14.4v) to voltage actually at the camper batteries (when the batteries actually need charging, so that there is substantial current in the wire). If charge voltage is less than 14v, trouble.

Several have posted charge circuit implementations that actually work: here's mine .

[adamis]

I think the answer to this question lies more specifically with the type of use you anticipate. If you are just going up to camp for a week or two a few times a year than I have to agree with HMS Beagle, run it on Propane. Not sure what type of tank setup you have but in my rig I have two of the standard BBQ tanks and I can go for easily a week if not two without needing to fill up.

That being said, if I was full timing (not sure if that is your case) I could understand why wanting to run on DC would be appealing. It's one thing to get your tanks filled up a couple of times a year, it's another to have to do it a dozens of times throughout the year.

As others have suggested, if you really need to run DC then you need to run the proper wiring to be successful. The question I don't think is dependent so much on your alternator but rather the wire used between the truck and the camper. If you get the right size wire then charging the camper from the truck shouldn't be an issue. That means a trip to the Home Depot and buying some 4, 2 or 1, AWG wire (do your research) and running it from your alternator to your camper (possibly bypassing the umbilical all together). You will of course want the charge controller to ensure the camper battery bank is being maintained properly.

[DWeikert]

The determining factor is the wire gauge from the alternator to the camper's battery. Most likely you still have factory wiring, maybe 10 gauge, possibly 12. Let's be optimistic and use 10 gauge and say 30 feet of it between the alternator and battery. That works out to a resistance of .03 ohms(R). Using Powerdude's figure of 15 amps(I) to run the fridge that means if the alternator is putting out 13.8 volts(E) the most the battery can be charged to is 13.35 volts due to .45 volts dropped across the wire(E=IxR). And that's assuming no stray resistance from wire connectors, the trailer plug, etc., and no other loads drawing current. To make matters worse if your battery is in need of a charge and is trying to draw say 25 amps charging current that lowers the voltage to 12.8. But, as the battery gradually takes a charge and draws less current, that will allow the charge voltage to increase, but never beyond the 13.35 due to the drop from the fridge current.

Now your 100W solar will help, but it isn't capable of supplying all the current the fridge needs so you'll still not get to a full charge while the fridge is on DC. You're probably going to get pretty close though unless you're starting out the trip with a really drained battery.

[HMS_Beagle]

The truck alternator is plenty big enough to run the DC fridge. The wiring from truck to camper is almost certainly not big enough, unless you have done a substantial upgrade. A 100 w solar panel will put out about 5 amps in all but ideal conditions, so it isn't big enough either. Just run it on propane - that's what they were designed to do.