Running trailer from tow vehicle inverter

rbpru wrote:
You can also do what I did to get an extra day out of my battery. I pulled the truck up to the TT and ran a set of jumper cables to the TT battery and charged it for 20 minutes off the truck.

You do what you have to do and while this is better than doing nothing the net gain will be minimal. It's the raison d'être for DC > DC chargers to even exist. ;)

If I had 120 volts available from my tow vehicle. I would plug a 3 stage battery charger into it, and charge the battery directly.

Clean and simple.

You can also do what I did to get an extra day out of my battery. I pulled the truck up to the TT and ran a set of jumper cables to the TT battery and charged it for 20 minutes off the truck.

Tomt53 wrote:
but it could extend camp time.

More likely what will happen is that you will run down the battery in the tow vehicle too......and leave yourself stranded.

NOT a good plan.

Small generators are NOT that expensive.
And some really are whisper quiet.....but not the cheapest ones.

boosTT wrote:
Why not just use jumper cables from the truck battery to the trailer battery?

SoundGuy wrote:
The truck's voltage regulator will limit voltage to well below what is necessary for a correct bulk charge - 14.4 to 14.8 volts, depending on the battery. This is where a DC > DC charger shines as it avoids this issue and will allow the trailer battery to bulk charge properly.

westend wrote:
That may not be accurate. A user would have to measure voltage/amperage with both batteries connected.

It is accurate ... voltage may initially be acceptable but will drop quickly, well below what is required for proper bulk charging. If were as easy as connecting jumper cables to recharge a trailer battery using the tow vehicle we'd all be doing it. There would also be no need for DC > DC chargers which avoid this issue entirely.

westend wrote:
It may be that using jumper cables pushes more amps into the depleted battery than the daisy chain of inverter->converter-> depleted battery. I know if I wanted to use my truck as a charging source for depleted batteries, I'd use jumper cables. I wouldn't expect to put a full charge into the battery, merely sufficient charge to power up necessary devices on an emergency basis.

I have a set of 4 gauge charging cables as well, not for recharging but to load support the trailer battery when it's under heavy load from the inverter. Works well for this purpose but not for restoring a depleted trailer battery.

Mine has no such restriction, the Duramax manual only says that it can cause high exhaust system temps which can cause a fire if parked over flamable material and that very extended running can cause problems with DPF regeneration as that can only happen over 30 mph. All sorts of industries leave trucks idling for more than a few hours at a time routinely.

I did learn something though, my truck might have a high idle setting, bumping idle to 1200 RPM for just such usage as we were discussing, and the electrical system does in fact have the ability to ramp up the idle speed if voltage sags.

SoundGuy wrote:

boosTT wrote:
Why not just use jumper cables from the truck battery to the trailer battery?

The truck's voltage regulator will limit voltage to well below what is necessary for a correct bulk charge - 14.4 to 14.8 volts, depending on the battery. This is where a DC > DC charger shines as it avoids this issue and will allow the trailer battery to bulk charge properly.

That may not be accurate. A user would have to measure voltage/amperage with both batteries connected. It may be that using jumper cables pushes more amps into the depleted battery than the daisy chain of inverter->converter-> depleted battery. I know if I wanted to use my truck as a charging source for depleted batteries, I'd use jumper cables. I wouldn't expect to put a full charge into the battery, merely sufficient charge to power up necessary devices on an emergency basis.

boosTT wrote:
Why not just use jumper cables from the truck battery to the trailer battery?

The truck's voltage regulator will limit voltage to well below what is necessary for a correct bulk charge - 14.4 to 14.8 volts, depending on the battery. This is where a DC > DC charger shines as it avoids this issue and will allow the trailer battery to bulk charge properly.

Tomt53 wrote:
Thank you, all. The purpose of using an inverter would be to boost the rv battery when it becomes low when dry camping, by running the tv and plugging the trailer into the inverter. I do not have a generator. I will be using a 1500w pure sine inverter. The converter in the rv has a smart charging system(Progreessive dynamics)- I know this would not be efficient, but it could extend camp time. I do have 2- 50 watt solar panels that keep the batteries up on the sunny days.

Yes that will work great. Keep in mind it will still take 2 to 4 hours to get a good charge (90%+) into a low battery.

Most owners manuals warn of extended idling. Small engines are made to be able to idle or run a steady RPM. Most Truck motors are not made to idle, even the newer diesel trucks have warning about idling.

The catalytic convertor will not reach it operating temperature, causing it to clog. The combustion will not be as efficient, leading to dirty valves, carbon build up in the combustion chambers. Plus someone can steal your truck. Not to mention it is illegal in some states.

I'm guessing if you did once or twice a year you might get away with it, but I would not idle any truck I cared about for long periods.

Just my .02

Why not just use jumper cables from the truck battery to the trailer battery?