Hi Folks... Ive been chewing on the idea of investing in Solar but have stayed away from it simply because we carry a 3000 watt inverter generator. trouble with this has been that often times on our last long road trip we never stayed in one place long enough to really top up the batteries and by the time we did get a place where we could plug in and bulk charge we had sucked out the batteries pretty deep - something I'd like to avoid doing again on this years trip.So...I have been thinking about using the truck to charge the 5th by running some decent copper (0/0 or 1/0) to the rear of the truck and using an anderson connector to make the connection to the trailer.questions / advice around how best to make this come together..the truck already has dual batteries, Im assuming there is a factory installed isolator - assuming.So, which battery would I hook up to ? would I install another isolator and where would that one go ? I figured I would simply install an isolator in the truck nearest the most convenient battery, perhaps a disconnect switch on the line in the 5verany other thoughts ?cheers.

I do not understand the problem. My TV charges my TT battaries when it is connected and the switch is on that is the truck is running. I assume the 5er does the same. Check your 7 pin plug. Pin #4 should be the 12 volt charging and pin # 2 should be ground.RV pin wiring

I would think you would tie in to the secondary battery. Isolators that I have seen are anywhere from 80-140 amp rated so they should allow a fairly high throughput but with the length of the run its hard to say how effective it will be. Most vehicle 7 pin connectors charging pin is fused at between 30 and 60 amps, but the power flow because of the wire limitations or loss dont allow anywhere near that much power. You didnt say how long you were at a given location running the battery down before moving and trying to charge, If it is several days I would think even a modest solar setup may do you as much good as this. And remember the solar panel on the roof will also be charging while you are moving as well as while stationary.

Two suggestions:You might already have a "charge line" from the truck to the 5er that is not working for some reason. A shop visit should answer that question.If your generator is built-in, you can run it while going down the road.Or just run it more often or longer when you are parked.

Your plan would help but by the time you buy the 1/0 wire and isolator you could buy 100 watts of solar. Not that 100 watts would be enough. How many days in a row do you dry camp? How many batteries do you have now? and how low do you discarge those batteries? Before I had solar I would nose my truck up to the RV batteries and use my jumper cables from the truck to the RV batts.BTW we carry a 2000 watt generator for back up but rearly use it.

TenOC wrote:I do not understand the problem. My TV charges my TT battaries when it is connected and the switch is on that is the truck is running. I assume the 5er does the same. Check your 7 pin plug. Pin #4 should be the 12 volt charging and pin # 2 should be ground.RV pin wiringwhile it is true that you are pumping a few amps down that wire into the plug, you really arent charging too much while you are driving.depending on the loads in the camper itself you are likely only carrying enough so as not to be discharging while driving.this may be enough for you, and has been for us but now as we boondock more and plug in less.

TV to Charge house while under way | Good Sam Community

theoldwizard1
Explorer II
May 23, 2017
MEXICOWANDERER wrote:
Get a digital multimeter
Drive truck minimum 10 miles to stabilize charging voltage
With engine running check voltage:Is it above 13.8 volts?
If yes your charging wire idea will work fine
If not it would take hours of driving to replace even -40 amp hours

This is what I have been saying all along ! It is HIGHLY UNLIKELY that you will be > 13.8V !

Actually, measuring voltage with no load is not very useful. You need a load. The old fashioned sealed high/low beam sealed head lamp was great for that.
MEXICOWANDERER
Explorer
May 22, 2017
http://www.grote.com/products/82-1042-heavy-duty-2-way-socket-plug-connectors-2-pole-plug-with-spring/

Even if you succeed in getting only a 15-amp charge rate out of trailer charging cable it is DOUBLE that of a 100-watt panel. Never heard of a hunting camp where there are no trees. One shadow and a panel is useless. Same for a cloudy day.
MEXICOWANDERER
Explorer
May 22, 2017
Get a digital multimeter
Drive truck minimum 10 miles to stabilize charging voltage
With engine running check voltage:Is it above 13.8 volts?
If yes your charging wire idea will work fine
If not it would take hours of driving to replace even -40 amp hours
There are FAR BETTER connectors than an Anderson Power Pole Connector for joining truck to trailer
The Anderson Power Poles I Have Seen Can Separate::Choose a dual prong trailer plug and socket
It is FAR FAR better to wire the charge lead DIRECTLY to the alternator
Use 6AWG to a new 60 amp breaker
You need 2nd breaker at trailer battery bank
Hope this helps
time2roll
Nomad
May 22, 2017
Truck should provide 5 to 10 amps without too much trouble. Basic trailer running the fridge on propane should draw one amp or less. This would seem to indicate an issue with the charge circuit from the truck. May not come close to fully charging the battery but certainly should run the basics and provide some charge. Clamp-on ammeter might be needed to discover where the power is going. Could also be an intermittent issue while in motion.

Still since you camp off-grid I think you will benefit from solar.
MudChucker
Explorer
May 22, 2017
theoldwizard1 wrote:
RoyB wrote:
Using a multimeter you you can tell by just measuring across the batteries terminals without the motor running and if the batteries are at 100 percent charge they will read 12.6-7VDC. Then turn your ignition on and start the motor. If the path for charging the batteries is good then you will see the DC Voltage across the battery terminals jump up to 13.6VDC or higher depending what your truck alternator setup is doing...

THIS TOPIC HAS BEEN COVERED A NUMBER OF TIMES !

First, 13.6V will NOT come close to fully charging a deep cycle battery that is at 50 percent state of discharge. Even 14.0V won't do the job ! Sure, if 13.6V is maintained it will not DISCHARGE further.

The short answer is, for "modern" (past 10-15 years) TV, YOU CAN"T GET THERE FROM HERE ! Modern vehicles use "smart charging" systems where the charging voltage will drop off to less than 14.0V shortly after the engine starts. 1/0 wire is not going to help this !

You need a DC-DC charger that will handle low (down to about 10V) input voltage. They exist, but none that I can personally recommend.

Thanks for that, thinking that solar might be the best solution...or mount the geny on the rear bumper and run the generator while we are underway.

Either way, i knkw that i have power on the 7 pin plug, but the loads in the camper suck that juice up leavimg very little to store in the trojans.
Sam_Spade
Explorer
May 22, 2017
corvettekent wrote:

BTW we carry a 2000 watt generator for back up but rearly use it.

So when a situation arises that you need it, it probably won't work.

They NEED to be run occasionally, for several reasons.
theoldwizard1
Explorer II
May 22, 2017
RoyB wrote:
Using a multimeter you you can tell by just measuring across the batteries terminals without the motor running and if the batteries are at 100 percent charge they will read 12.6-7VDC. Then turn your ignition on and start the motor. If the path for charging the batteries is good then you will see the DC Voltage across the battery terminals jump up to 13.6VDC or higher depending what your truck alternator setup is doing...

THIS TOPIC HAS BEEN COVERED A NUMBER OF TIMES !

First, 13.6V will NOT come close to fully charging a deep cycle battery that is at 50 percent state of discharge. Even 14.0V won't do the job ! Sure, if 13.6V is maintained it will not DISCHARGE further.

The short answer is, for "modern" (past 10-15 years) TV, YOU CAN"T GET THERE FROM HERE ! Modern vehicles use "smart charging" systems where the charging voltage will drop off to less than 14.0V shortly after the engine starts. 1/0 wire is not going to help this !

You need a DC-DC charger that will handle low (down to about 10V) input voltage. They exist, but none that I can personally recommend.
KD4UPL
Explorer
May 22, 2017
It won't matter which truck battery you hook to, they are wired in parallel. There is no isolator between them. You would want an isolator between your heavy duty charge wire and the the truck. I would use a voltage controlled relay, also known as an automatic charge relay (ACR) Blue Sky makes a good one I've used a couple of times. The old timey diode based isolators will drop the charge voltage by .7 volts.
Before doing anything I would verify that your factory charge wire is hooked up and working. Fixing that may be all you need to do. Yes, it's a limited charge but it may be enough depending on your usage.
RoyB
Explorer II
May 21, 2017
Using a multimeter you can tell by just measuring across the batteries terminals without the motor running and if the batteries are at 100% charge they will read 12.6-7VDC. Then turn your ignition on and start the motor. If the path for charging the batteries is good then you will see the DC Voltage across the battery terminals jump up to 13.6VDC or higher depending what your truck alternator setup is doing...

If you don't see the jump in 12VDC voltage then your truck start system is NOT charging the external batteries...

On my truck and connected trailer I had to install a RELAY and a FUSE to my truck fuse panel to get the "TRAILER CHARGE" to work for me. It was in an envelope in the truck glove box with not markings what it was for... Finally found it in my truck manual and where to plug in the the fuse and relay module...

You may have the same situation there????

Your trailer/house system may be wired through a battery disconnect switch which you engage when when in travel mode and this may break the connection for you to keep the batteries charged from the truck alternator setup???

Look for the increased 12VDC when the truck motor is running...

Roy Ken
down_home
Explorer II
May 21, 2017
our last f350 twin alternators had a20 amp fused wire to 4 wire plug expressly to charge house batteries. i understand that is the way with all of the designs of tow vehicle tow plug harnesses as most towables do no have a generator