Do you use your alternator to charge your travel trailer batteries?

[Cliffy]

My comments were not intended to say that the batteries were "fully" charged ( I am fully aware that 13.6 won't give a 100% battery fill) That's why I said 90%. One can operate several days with a 90% charge every day or 2. I was refering to "useful" charge not technically 100%. I doubt more than 5% of the rigs on the road ever get 100% charging.

Likewise, I also realize that the alternator senses the TV battery to set its charging rate and not what maybe a lower charge TT battery. But the system as designed does work if one moves every day or so or if its just a one nite stopover at Wally World. Now, as you say, it might be different on newer TVs I'll find that out later this year with a new TV.

My point being that I can get to 100% (or very close to it) in 1 overnight with hookups on the Xantrex but with towing the TV will bring them up to a useful point if I want to dry camp for a nite or 2.

Yes, after much research the Xantrex and one other charger were acceptable to me for recharge of my batteries. Full 3 stage design with priority for 14.4 volt charging until about 80-85 % full charge passing in my case a min of 20 amps for 3 -4 hrs (35+ amps if the batteries are that low). Its a 40 Amp charger. My criteria was no longer than 4 hrs to recharge my batteries on a SMALL portable genny and not to have to run all day. Unlike the WFCO, its programming allows what I want. BTW, there is some question about 14.4 and higher voltages for charging even by Trojan.

The WFCO charger that came with the rig NEVER gets to anything above 13.6 volts and single digit amps as its designed to be hooked up the shore power 100% of the time. The batteries are only secondary to its design parameters.

[DJHphoto]

Originally Posted by Cliffy

OK a reality check- It really pays to test a system before you postulate on how it works. I did just that. 2006 F-150 with a 2019 TT.
I have a battery monitor hooked up to the TT batteries ( 2 6 volt GC batteries).

After a night dry camping I can see as high as 14 amps going into the battery just from the trucks wiring. It usually starts off at about 14.1 volts and then drops to the high 13 volt range. After 4 or 5 hours of running I see 13.4 to 13.6 volts and amps at 1 or 2 going into the battery telling me the battery is getting topped off. I have even checked the monitor readings with a clamp on meter on the battery positive lead at the battery. A double check.

I can recharge to about 90% or higher on my driving trip to the next destination.

When I plug in ground power I see again maybe 2 or 3 amps in in the mid 13 volt range (by my Xantrex 40 charger) telling me again my battery is about full just from driving. If it wasn't I'd be seeing 14.4 volts and 30 amps or more from the Xantrex.

SO, by actually testing the system I have determined that it is possible to recharge while driving. Test your system before you invest in other technology. A good battery monitor is worth its weight in gold.

Very good advice. Would you post a link to the good monitor you use? Where is it mounted?

[RobE]

https://www.ebay.com/itm/Battery-Isolator-Separator-12V-140A-Vehicle-Automotive-Battery-Management-Kit/113243161075?hash=item1a5dd181f3:g:a0UAAOSw0lVa9AD G:rk:9f:0

[Cliffy]

I bought a wireless one off the internet. It works very well. It uses a transmitter that I mounted in the fwd storage compartment just above the plus battery lead. I ran the plus lead up through the floor and back out again.
I mounted the screen by the electrical control panel in the TT and powered it with a wire pick up behind the control panel.
It is very accurate as I've checked it numerous times with a hand held clamp on meter.

[Varago]

could please post info on the unit

[Cliffy]

I'll see if I can find the info
It was cheap but it seems accurate

[SV Tom]

If the 12 volt outlets on generators that have cables with battery connectors on them are not meant for charging batteries what are the meant for ?

[twinboat]

Originally Posted by SV Tom

If the 12 volt outlets on generators that have cables with battery connectors on them are not meant for charging batteries what are the meant for ?

They can charge batteries but at only 8 amps. You will need to run the generator for 8 to 10 hours to charge a lightly discharged battery bank. Then you need to worry about overcharging.

You can plug a 50 amp smart charger into the 120 volt outlet and charge a battery in a few hours.

[JM0278]

Got our TT last summer and quickly installed a Victron bluetooth battery monitor. Before connecting the truck, the monitor showed the single group 31 house battery down 32Ah at 12.1 volts. After connecting the truck, it showed a charge of 20 amps at 13.34 volts with "Tow Mode" engaged. We drove for perhaps an hour at mixed speeds, but no more than 55 mph, and upon reaching our destination, the Victron showed the battery was down 19Ah so a one hour drive at moderate speeds replaced a bit more than 12Ah. That's more than a trickle.

[FL420]

Originally Posted by twinboat

They can charge batteries but at only 8 amps. You will need to run the generator for 8 to 10 hours to charge a lightly discharged battery bank. Then you need to worry about overcharging.

You can plug a 50 amp smart charger into the 120 volt outlet and charge a battery in a few hours.

Originally Posted by twinboat

They can charge batteries but at only 8 amps. You will need to run the generator for 8 to 10 hours to charge a lightly discharged battery bank. Then you need to worry about overcharging.

You can plug a 50 amp smart charger into the 120 volt outlet and charge a battery in a few hours.

I boondock a lot but don't have solar. This is what I use to keep both house and battery banks charged without using my 8KW Onan generator. It's a lot cheaper and I can run into town in the toad for gas a lot easier than driving the coach in for diesel.

Hooking up straight to the battery terminals with the smart charger is much faster and more efficient than using the the 8 amp outlet on the the generator or powering the whole coach just to use the coach's charger.

[heatherdawnc]

A circuit/isolator to charge the TT batteries from the tow vehicle alternator is actually quite simple.

One important point is that the TT batteries become isolated while the vehicle starter is engaged. An example of this is the radio turning off while the starter is engaged. Simple concept used on vehicles for decades. In fact that wire going to the radio is perfect to actuate the isolator relay.

List of material

1. 6 gauge battery cable. (this should be sufficient unless you wish to be able to jump start the vehicle with the TT batteries. Enough to reach the rear bumper and also from the tongue to the TT batteries

2. Isolator relay (Riding lawn mower starter relay is suitable. Auto parts stores have mower parts- filters, relays, etc.)

3. Quick disconnect for the cables at the rear of the truck. (You can find suitable QDs on eBay if not at your favorite auto parts store.)

4. Various wire connectors and lugs and some 16 awg (gauge) wire, zip ties, etc.


Procedure


Positive (+) cable and relay

1. Install the relay somewhere close to the truck battery

2. Run a short piece of 6 gauge from the positive (+) terminal to one of the large terminals on the relay.

3. Run a length of 6 gauge to the rear bumper and install QD for the (+) connection.

4. On one of the small terminals on the relay run a 16 awg (gauge) ground wire.

5. On the other small terminal run a 16 awg to any "accessory" circuit. The radio accessory wire is fine. That's what I used. You can access this at the fuse box.

NOTE: Radios have 2 power wires. One is switched and comes though the Accessory side of the ignition. One is always HOT to maintain station memory etc. Be certain to use the accessory wire NOT THE ALWAYS HOT.

6. Install 6 gauge ground (-) cable and QD. This ground should be bolted directly to the frame at the rear of the truck.

7. Run cables and QDs on the TT to the TT batteries.


Now the Travel Trailer batteries will be isolated while the starter is engaged or the ignition is off and active while the engine is running

[twinboat]

Originally Posted by heatherdawnc

A circuit/isolator to charge the TT batteries from the tow vehicle alternator is actually quite simple.

One important point is that the TT batteries become isolated while the vehicle starter is engaged. An example of this is the radio turning off while the starter is engaged. Simple concept used on vehicles for decades. In fact that wire going to the radio is perfect to actuate the isolator relay.

List of material

1. 6 gauge battery cable. (this should be sufficient unless you wish to be able to jump start the vehicle with the TT batteries. Enough to reach the rear bumper and also from the tongue to the TT batteries

2. Isolator relay (Riding lawn mower starter relay is suitable. Auto parts stores have mower parts- filters, relays, etc.)

3. Quick disconnect for the cables at the rear of the truck. (You can find suitable QDs on eBay if not at your favorite auto parts store.)

4. Various wire connectors and lugs and some 16 awg (gauge) wire, zip ties, etc.


Procedure


Positive (+) cable and relay

1. Install the relay somewhere close to the truck battery

2. Run a short piece of 6 gauge from the positive (+) terminal to one of the large terminals on the relay.

3. Run a length of 6 gauge to the rear bumper and install QD for the (+) connection.

4. On one of the small terminals on the relay run a 16 awg (gauge) ground wire.

5. On the other small terminal run a 16 awg to any "accessory" circuit. The radio accessory wire is fine. That's what I used. You can access this at the fuse box.

NOTE: Radios have 2 power wires. One is switched and comes though the Accessory side of the ignition. One is always HOT to maintain station memory etc. Be certain to use the accessory wire NOT THE ALWAYS HOT.

6. Install 6 gauge ground (-) cable and QD. This ground should be bolted directly to the frame at the rear of the truck.

7. Run cables and QDs on the TT to the TT batteries.


Now the Travel Trailer batteries will be isolated while the starter is engaged or the ignition is off and active while the engine is running

A lawnmower starter relay isn't continuous
duty. That style is used to engage the starter motor for a minute or so. It will overheat if left on, and fail in a short time.

Still a solid plan, but you want to use a solenoid rated for continuous duty. They can remain on hours.

[LargeMarge]

Our rig == 1997 Ford CF8000 ExpeditionVehicle.
8.3 Cummins mechanical, 250-amp large-case continuous-duty alternator.
No genset.

We mounted a pair of semi tractor-to-trailer plugs to maintain the towed vehicle batteries. The plugs and curly cable == massive... probably in the neighborhood of 2-gauge or better. This system is dedicated to charging, separate from the lights/brakes 7-pin.

We foraged the kit at Anderson Brothers Heavy Truck dismantlers in Eugene Oregon. I wouldn't hazard a guess as to the vintage; I doubt we paid more than twenty Federal Reserve Promissory Notes for the whole shooting match.

Would something like this fit your bill?

[THenne1713]

Originally Posted by Lstyles

In an RV you can easily use your alternator to charge the batteries as the wire run would be short. However, it would seem to be much more difficult to use the Tow vehicle alternator to charge a travel trailer. I understand that you might get some trickle charge across the wiring harness set up for trailer lights but the gauge would be way too small to get much. Do people fashion thick gauge wire/cable across the hitch point to try and charge the trailer battery? It seems like that would be risky.
Thoughts?

The 7-wire trailer plug has a B+ that you run a FUSED/ protected wire by RELAY (IGN controlled) from tow battery to harness, and also FUSE/ protect on TT battery end. Suspect #10 (30a) wire? e-TRAILER SAYS min #12