charging the Airstream while being towed

[thebreezeman]

How much charge could I expect my f150 to put into my airstream while cruising down the highway?

[overlander63]

Probably no more than 7-10 amps, and most likely less. Usually much less.

[Bill M.]

You might get the battery up to 11.5 volts or so. It really does not charge much while driving. There is just too many feet of small wire between the alternator and the trailer battery.

[jpons]

Is this a factor of the F150? My Toyota 4Runner will fully charge my two coach batteries in a days drive from being nearly depleted.

[HiHoAgRV]

Both of my trailers have multiple batteries of 220AH-ish capacity and trimetric battery monitors. The usual charge is 2 - 4% of the overall capacity. If my morning level is 90%, by the time I park I've climbed to 92ish%. Thats about the same as my wimpy 60W solar panel.

All of that said, not too much charging goes on in my trailer.

6 hours of bulk charging on a 3 stage is much different from 6 hours of float from a truck.

You milage may vary

[J. Morgan]

My Silverado puts a full charge on my two 100 amp hour batteries after a day of driving.

I know that the wire that goes to the pigtail originates from stud 1 in the under hood power distribution box and is fused for 30 amps.

I have a 20 amp auto reset circuit breaker at the trailer battery to make sure I don't pop fuses.

[AtomicNo13]

My Excursion will fully charge a battery from 75% in about 5 hours, that's a full days drive for me.

[87MH]

Thanks to all for sharing your numbers.

CA_Tallguy did a great write up on installing the proper wire size between the alternator and the trailer battery.

With a Great Adventure coming up later this year I need to look into what I can do to maximize the charge rate on the '78 31' Sovereign .

Everyone should be encouraged to measure, at least once, what the charge voltage actually is after travelling 30' or so through the 14 gauge wire looms supplied by the vehicle manufacturers.

[Jammer]

Originally Posted by thebreezeman

How much charge could I expect my f150 to put into my airstream while cruising down the highway?

Hmmm... Maple Grove... just up the road.

The reported experiences with the charge line vary widely. It depends on the way the tow vehicle is wired, the condition of the trailer connector, the number, size, and condition of the trailer batteries, and how discharged the trailer batteries are.

The best thing to do is measure the current on your setup and see if you're happy with it. I check mine before every trip where I'm depending on the charge line, because things like relays and fuses can fail and render it inoperative.

I've planned out the addition of an ammeter to my tow vehicle, specifically for measuring trailer charge amps, but haven't yet spent the time and money to put it in. So I use a handheld meter while parked.

[Tyvekcat]

Interesting question. I will check my brothers F-150 (06) model and see if it has a heavy duty alternator. It has one battery.
My Dodge Ram Diesel has a heavy duty rated alternator and dual batteries. There is the potential of more current available, but like 87mh says "wire size matters"
I think last time I measured the voltage on the trailer batteries it was 13.5 volts @ idle. I was just testing and using a new meter. I should check that more often.
I guess the largest current draw is when you connect to the truck, if your trailer batteries are drained somewhat ?
My guess is at that time when you connect you could draw too much and pop a fuse? I seem to remember reading something about that on Dodge's, I need to look that up. Glad you brought this up.

I never had any issues with my previous trailer. It had two deep cycle 12volt marine batteries, and my new International has two Interstate marine batteries. Four batteries all connected. That is a lot of current available. Kinda scary.
Airstream and my previous trailer are always on the Battery Tender, when not connected to 'go'.
They all seem to get along good. I am going out to look for the schematic and find that fuse.
Best regards

[Jammer]

Originally Posted by Tyvekcat

I guess the largest current draw is when you connect to the truck, if your trailer batteries are drained somewhat ?

The largest current flow is typically the reverse flow while the starter is engaged in the truck, unless the batteries are disconnected by a relay or isolator at that point.

The largest forward flow occurs in the first minute or so after the engine is started, because there is no surface charge on the batteries. Obviously, the current is greater the further discharged the batteries are. Operating 12v lights and appliances in the trailer will also cause the current to increase.

To test the charge line, I leave all the lights and fans on in the trailer for half an hour or so, then start the engine in the TV, and measure the current.

My guess is at that time when you connect you could draw too much and pop a fuse? I seem to remember reading something about that on Dodge's, I need to look that up. Glad you brought this up.

Yes, that can be a problem. I use an automatic-reset circuit breaker. Since those sometimes fail, I also have a 100 amp fuse in series with it.