Tow vehicle charging RV battery

[Country Campers]

From a recent post on not allowing the tow vehicle to try to charge a lithium battery it has raised a question or 3. Also from reading a few other posts on some other brand forums which has raised some other curiosities.

Will allowing the tow vehicle to charge a lithium battery damage the alternator in the tow vehicle?

The lithium battery can hold about 14 v dc and a lead acid found in a tow vehicle is around 12.7 v , does this cause any issues?

While traveling is it possible that the lithium battery could be pushing power, amps or voltage, into the tow vehicle battery?

These are all question pertaining to a stock tow vehicle with no dc to dc charger installed into the RV.

Any other thoughts please share.

Brian

[ncitro]

From a recent post on not allowing the tow vehicle to try to charge a lithium battery it has raised a question or 3. Also from reading a few other posts on some other brand forums which has raised some other curiosities.

Will allowing the tow vehicle to charge a lithium battery damage the alternator in the tow vehicle?

The lithium battery can hold about 14 v dc and a lead acid found in a tow vehicle is around 12.7 v , does this cause any issues?

While traveling is it possible that the lithium battery could be pushing power, amps or voltage, into the tow vehicle battery?

These are all question pertaining to a stock tow vehicle with no dc to dc charger installed into the RV.

Any other thoughts please share.

Brian

I ran my setup without a DC to DC charger for about a year. This was for Lion Energy batteries with the factory truck wiring. I had no issues at all, just wanted to increase my charge rate off the truck. My truck does have dual heavy duty alternators, and Ford does have the trailer charge wire setup to be keyed with the ignition so keep that in mind.

I suppose if I had the key in but engine not running current might run from the trailer to the truck, but once running the alternator was high enough voltage that while not optimal, I don’t think it would be low enough to allow current to flow that way.

[Guest]

From a recent post on not allowing the tow vehicle to try to charge a lithium battery it has raised a question or 3. Also from reading a few other posts on some other brand forums which has raised some other curiosities.

Will allowing the tow vehicle to charge a lithium battery damage the alternator in the tow vehicle?

The lithium battery can hold about 14 v dc and a lead acid found in a tow vehicle is around 12.7 v , does this cause any issues?

While traveling is it possible that the lithium battery could be pushing power, amps or voltage, into the tow vehicle battery?

These are all question pertaining to a stock tow vehicle with no dc to dc charger installed into the RV.

Any other thoughts please share.

Brian

Brian,

To answer your questions.

The lithium battery can backfeed any time the voltage at the TV is lower. Since smart alternators can reduce voltage at various stages, this could be possible where this alone will not cause an issue. Where the issue arises, is when the TV is idling and the lithium battery is drawing excessive amounts of current. Since calibrators would not calibrate systems to account for a lithium battery in a trailer, the diodes in the alternator could be overheated with high loads at low airflow. This came directly from an alternator maker. They suggested a DCDC and to charge while underway, since an alternator needs adequate airflow through the front of a moving vehicle to achieve proper cooling. Also your GM truck will deliver higher voltages while tow haul mode is active. If however tow haul is active and the headlights are turned on, the voltage increase is negated.

If your connected while the TV is turned off, the lithium pack will backfeed to the TV and will lose voltage over time.

Jim