Inverter charging the camper from the trucks batteries.

ppine wrote:
Effeciency is a big issue and voltage drop. You also probably do not want 120 volts in your engine compartment. If your truck is 12v and your trailer or camper are 12v I don't get the point except for a sort of parlor trick.

No parlor trick. Looking for a best fit for our use.

Not sure what you mean by efficiency is a big issue. There would be a small amount of inefficiency converting back and forth 120v and 12v but that inefficiency does not come that expense of battery charging in the camper. It would be wasted alternator potential and diesel fuel. Not sure that would be noticeable at the pump. In general the solar panels provide what we need and would be charging simultaneously with the inverter on the truck This would be used only when we need it through heavy draining of the batteries from running air conditioning or prolonged cloudy days.


As I mentioned above the main reason is to allow me to use the campers inverter/charger with its programmable charging profile specific to Lithium batteries. Otherwise a dc-dc battery charger that is programmable for lithium will be needed. I am looking for something that can pass more than 100 AH dc. At 100Ah I would need 2/0 cable to stay just under 3% line loss. Line loss at 120v would be less that .3%

There are some specialty programable lithium capable dc-dc products out there but the cost is similar to decent inverter and I am having a hard time finding people with specific experience using them. Having an inverter on the truck could also be handy for making 120v power when we don't have the camper with us.

It works fine. We've used this method as a work around for a 5th wheel when the truck wiring encountered a road gator.

It should work just fine. I carried my camper on a truck with an inverter but I never plugged it into the inverter. I just ran some #2 cable from the truck battery to the 7 pin connector for the camper. The final 6 inches was #8 so it would fit in the 7 pin connector. It charged well enough like that.

Effeciency is a big issue and voltage drop. You also probably do not want 120 volts in your engine compartment. If your truck is 12v and your trailer or camper are 12v I don't get the point except for a sort of parlor trick.

work2much wrote:
Thoughts?

Go for it :)

You're correct about efficiency, who cares in the case you describe.

You're only out cost, is the cost of your inverter a better trade off than a thicker wire?

I'm not sure about the "more stable power" statement. Modern cars have so many low voltage processors and associated circuitry the power needs to be well behaved at the alternator (by that I mean no overshoot when going from heavy to light loads and back).

But I agree with you that your system can provide absolute control over the charging voltage. If using LiFePO4, would be a good advantage.

No way would I put the inverter in the engine compartment! Unless all the components inside the inverter are auto grade certified for 125C or 150C. Would need to search for an "underhood" rated inverter, which if they exist will be pricey.

Dave

Running 120V cable from truck to camper would be my biggest worry.
My truck has factory 350W inverter build in it. I already tested that my small shop compressor will run on it and am considering using it for refrigerator power while on the road.
But drilling holes for cable and putting safe grommets stops me on the idea.
You also have to think about "senior moment" when you can forget to unplug while unloading TC.

cewillis wrote:
Good idea for reducing transmission loss but, imo,

loss of efficiency converting 12v to 120v and back to 12v

negates the advantage.
I would, and did, stick with the native 12v connected through 2 gauge wire.

Wouldn't the efficiency loss be realized only in fuel economy which should be inconsequential? The inverter should be delivering a high quality power source to the charger as if being plugged in.

The other issue I have is that I would need to purchase a voltage regulator of some sort to make the alternator voltages friendly to my lithium battery. Currently our trucks batteries are in no way connected to the campers battery for that reason.

Good idea for reducing transmission loss but, imo,

loss of efficiency converting 12v to 120v and back to 12v

negates the advantage.
I would, and did, stick with the native 12v connected through 2 gauge wire.