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Author Topic: Will my tow vehicle charge my trailer battery?  (Read 69424 times)

Twistedlarch

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Will my tow vehicle charge my trailer battery?
« on: June 06, 2013, 07:01:54 PM »
Hi all

I keep getting mixed answers on whether or not my tow vehicle will charge my tent trailers battery while in tow.  I have a 2011 Tundra 5.7 liter TRD with factory installed tow package that is pre-wired for a brake controller. 

I've called tow local hitching stores and they say "YES", but RV dealerships say "MAYBE".   ::)
I'm getting ready for it's first trip "OFF" the grid and would like to have a fully charged battery when I arrive to my destination.  Is there anyway I can check myself whether or not my truck has this feature?

My trailer is a 1998 Viking 2490 Tent Trailer.

Thanks
Truck: 2011 Toyota Tundra 5.7L TRD 4x4
         1988 Ford F250 7.3L Diesel 4x4
 
Trailer: 1998 16' Viking Legend 2490 Tent Trailer

Wigpro

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Re: Will my tow vehicle charge my trailer battery?
« Reply #1 on: June 06, 2013, 07:11:46 PM »
On a normal 7 pin plug the 12 volt charging line is pin 4....if you have 12 volts coming from the truck and matching on the trailer you more than likely are wired to charge...however, don't expect a ton of charge with the wire distance it doesn't charge much.

You can make sure it is charged before you leave and if nothing needs 12 volt in the trailer, disconnect the battery and it should be full when you get where you are going. But if you are running a fridge on propane, you will need the 12 volts hooked up.

Hope this helps...

Jim
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Great Horned Owl

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Re: Will my tow vehicle charge my trailer battery?
« Reply #2 on: June 06, 2013, 07:25:07 PM »
It is also not unlikely that the fuse for the charge line in the tow vehicle was never installed.

Joel
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Twistedlarch

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Re: Will my tow vehicle charge my trailer battery?
« Reply #3 on: June 06, 2013, 11:45:46 PM »
Thanks for your help, I'm brand new to the RV scene so I know nothing  :-\

I'm looking at a 3.5-4 hour drive to my destination.  I want to run the lights at night for a few minutes and the water pump every now and then.  I'm hoping I can make my battery last for the four days, I have a Napa 8270 Deep cycle (180 BRC). 

As for the fridge, I thought I could run it on just LPG, is this not possible?  It has two switches to turn 12v or 120v off

Thanks
Brian
Truck: 2011 Toyota Tundra 5.7L TRD 4x4
         1988 Ford F250 7.3L Diesel 4x4
 
Trailer: 1998 16' Viking Legend 2490 Tent Trailer

John From Detroit

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Re: Will my tow vehicle charge my trailer battery?
« Reply #4 on: June 07, 2013, 05:55:25 AM »
This is one of the few times I have read a statement by an RV dealership which I agree with 100%,  Maybe is the answer

Some vehicles with the "Tow package" Provide a charge line some do not
Some tent trailers can take advantage of it , some can not.

The only way to be sure is testing

IF the tow vehicle has a 7 pin (Usually round) or six pin connector, With trailer NOT connected measure, either with a test lamp or volt meter, each flat pin to ground (The hitch is usually a good ground) if you get full battery voltage or bright light then the wire needed is there.

Check the SAME contact, on the tow-vehicle socket, with the engine running.   (Use the light for this one) and again if the light lights, the lead is there.
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Twistedlarch

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Re: Will my tow vehicle charge my trailer battery?
« Reply #5 on: June 07, 2013, 07:57:19 AM »
Thanks John!   :D
Truck: 2011 Toyota Tundra 5.7L TRD 4x4
         1988 Ford F250 7.3L Diesel 4x4
 
Trailer: 1998 16' Viking Legend 2490 Tent Trailer

Alfa38User

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Re: Will my tow vehicle charge my trailer battery?
« Reply #6 on: June 08, 2013, 08:36:32 AM »
Quote
As for the fridge, I thought I could run it on just LPG, is this not possible?  It has two switches to turn 12v or 120v off

Again, another ambiguous answer!! It depends!! I am not sure from your description if you meant that you have a 3 way fridge or not. Knowing the  Make and model of the fridge in question would help a lot in getting the best answer.

(A 3 way fridge cools under 120V (plugged in), under the 12V Battery,  or by using propane (LPG)). Many today are only 2 way, 120V electric or propane but yours is old enough to be a genuine 3 way and cooling using 12V alone is bound to be hard on the battery. It is, after all, a heater element.

Anyway, the unambiguous answer is, YES, you can cool using propane (LPG) but not alone!!. The hooker is that most RV type fridges require 12V to power their circuit board but burn propane to do the actual cooling. Without the 12V nothing works. The 12V draw under these conditions is negligible as is the propane required. Whether the 12V switch removes the 12V power to the circuit board under these conditions or not, I don't know....
« Last Edit: June 08, 2013, 01:12:14 PM by Alfa38User »
Stu
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Snowbird, Naples Florida
Alfa Gold 38 (2000) 5ver (parked!)

"Of course I talk to myself, sometimes I need expert advise!!!"

Twistedlarch

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Re: Will my tow vehicle charge my trailer battery?
« Reply #7 on: June 09, 2013, 09:04:19 AM »
Again, another ambiguous answer!! It depends!! I am not sure from your description if you meant that you have a 3 way fridge or not. Knowing the  Make and model of the fridge in question would help a lot in getting the best answer.

(A 3 way fridge cools under 120V (plugged in), under the 12V Battery,  or by using propane (LPG)). Many today are only 2 way, 120V electric or propane but yours is old enough to be a genuine 3 way and cooling using 12V alone is bound to be hard on the battery. It is, after all, a heater element.

Anyway, the unambiguous answer is, YES, you can cool using propane (LPG) but not alone!!. The hooker is that most RV type fridges require 12V to power their circuit board but burn propane to do the actual cooling. Without the 12V nothing works. The 12V draw under these conditions is negligible as is the propane required. Whether the 12V switch removes the 12V power to the circuit board under these conditions or not, I don't know....

Thank you Alfa

My fridge is indeed a 3 way, I just figured that out yesterday.  I think I'm going to have to just use the old Ice chest for this 4 day trip coming up   :D

As for the charging system, my voltage meter appears to NOT be working, I can't get any response from any of the post on my plug.  I tried several grounding areas but nothing. I hooked up the pig tail to the truck and everything works  ::)

Brian
Truck: 2011 Toyota Tundra 5.7L TRD 4x4
         1988 Ford F250 7.3L Diesel 4x4
 
Trailer: 1998 16' Viking Legend 2490 Tent Trailer

Alfa38User

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Re: Will my tow vehicle charge my trailer battery?
« Reply #8 on: June 09, 2013, 11:10:02 AM »
Did I mention that the make and model of the fridge would be helpful??? We might be able to find the documents on it.!! :(

There are many cheap multi-meters available at Radio Shack etc but some are just that ..... cheep!!
One alternative for more rugged use is a mechanics test light, looks like an ice pick with a wire attached (for the ground pickup) and a light in the handle, available at most auto parts suppliers. I used a "homemade version" for many years of circuit tracing on the job and seldom used the voltmeter on 52V DC circuits!!

Have fun camping!!!
« Last Edit: June 09, 2013, 11:11:56 AM by Alfa38User »
Stu
Montréal, Canada 🍁
Snowbird, Naples Florida
Alfa Gold 38 (2000) 5ver (parked!)

"Of course I talk to myself, sometimes I need expert advise!!!"

Twistedlarch

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Re: Will my tow vehicle charge my trailer battery?
« Reply #9 on: June 09, 2013, 10:36:45 PM »
Did I mention that the make and model of the fridge would be helpful??? We might be able to find the documents on it.!! :(

There are many cheap multi-meters available at Radio Shack etc but some are just that ..... cheep!!
One alternative for more rugged use is a mechanics test light, looks like an ice pick with a wire attached (for the ground pickup) and a light in the handle, available at most auto parts suppliers. I used a "homemade version" for many years of circuit tracing on the job and seldom used the voltmeter on 52V DC circuits!!

Have fun camping!!!


Here's a picture of the tag I found inside the fridge.

Truck: 2011 Toyota Tundra 5.7L TRD 4x4
         1988 Ford F250 7.3L Diesel 4x4
 
Trailer: 1998 16' Viking Legend 2490 Tent Trailer

Alfa38User

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Re: Will my tow vehicle charge my trailer battery?
« Reply #10 on: June 10, 2013, 09:06:21 AM »
... And here is the document that tells you more than you really wanted to know about that model, including how to operate it on LP alone!!!

https://www.dometic.com/ed505e90-e109-4bbb-b942-784fee053651.fodoc

Forget the ice chest, except perhaps to keep the extra beer cold!!!!
« Last Edit: June 10, 2013, 09:18:50 AM by Alfa38User »
Stu
Montréal, Canada 🍁
Snowbird, Naples Florida
Alfa Gold 38 (2000) 5ver (parked!)

"Of course I talk to myself, sometimes I need expert advise!!!"

Twistedlarch

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Re: Will my tow vehicle charge my trailer battery?
« Reply #11 on: June 10, 2013, 09:25:33 AM »
... And here is the document that tells you more than you really wanted to know about that model, including how to operate it on LP alone!!!

https://www.dometic.com/ed505e90-e109-4bbb-b942-784fee053651.fodoc

Forget the ice chest, except perhaps to keep the extra beer cold!!!!

Thank you very much!!  :D
Truck: 2011 Toyota Tundra 5.7L TRD 4x4
         1988 Ford F250 7.3L Diesel 4x4
 
Trailer: 1998 16' Viking Legend 2490 Tent Trailer

Shadow Catcher

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Re: Will my tow vehicle charge my trailer battery?
« Reply #12 on: October 21, 2013, 07:49:46 PM »
Easiest way to check is a VOM/Multimeter at the battery I have a Harbor Freight meter that stays with the trailer. Voltage with vehicle not plugged in, voltage with TV plugged in and engine running should be higher.

BigSkyTrailerGuy

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Re: Will my tow vehicle charge my trailer battery?
« Reply #13 on: March 06, 2014, 09:41:07 PM »
Sorry, but I'm going to add my own nebulous answer.  Will it charge?  Yes.  Is it charging your batteries to 100%, almost definitely NO (depending on your battery)  Deep cycle batteries may need a good 48 hours of charging to get back up to 100%.  And if they've only been charged up to 50% forever, they'll never make it back to 100%

Jim Godward

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Re: Will my tow vehicle charge my trailer battery?
« Reply #14 on: March 08, 2014, 04:18:42 PM »
The time to charge and the amount of charge are related to the size of the wire and the distance between the charger(Alternator) and the battery.  I normally use at least a no. 8 gauge wire for this application.  I suspect the wiring that you have is no 12 or most probably 14 gauge wire.  Once you figure out whether you have charging or not, if you have charging measure the voltage at the alternator and at the battery.  The difference will tell you and us how good the charge will be.  Hopefully a good, greater than 90% charge.  Anything less and you should get a battery charger and use it to charge the batteries.

Answer the charge question and we can provide additional help estimating the charge from the alternator.
Jim
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robertusa123

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Re: Will my tow vehicle charge my trailer battery?
« Reply #15 on: May 23, 2014, 06:38:42 AM »
I new someone that justvadd a cigarette lighter plug with a long wire and just plunged the battery into the rear power socket whial towing.   It charged the batterie whial driving and he didn't haft to rewire the trailer light conecter or tow vehical
1996  26ft. 3 kids 2 dog and the wife too

lifespeed

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Re: Will my tow vehicle charge my trailer battery?
« Reply #16 on: August 13, 2014, 08:06:31 PM »
Bit of a late reply here, but hopefully some useful information.  The answer is "it won't charge to 100% capacity".  This of course assumes the connector is wired for 12V power on both TV and trailer sides.  One should be aware that lead acid battery capacity and useful life are significantly degraded by not charging to 100% capacity, or discharging below 50% capacity.

I'll try to keep this short.  Depending on the battery, a full 100% charge can require 14.8V.  Your tow vehicle alternator absolutely does not do this as it was not designed to charge deep cycle batteries.  It probably only puts out 13.8V to 14V, and then there is voltage drop along typically under-sized wires.  Deep cycle batteries also want a specific charging behavior, do a search on "three stage charger for lead acid batteries".  "Charging" from a TV alternator simply by connecting an undersized wire will consequently take forever, and at best get you to maybe 80% capacity.  But you only want to discharge down to 50%, so this is a major shortcoming.

I learned all this as part of installing a setup to accomplish rapid battery charging to 100% capacity from my tow vehicle, but I spent some money and effort to do so.  I use a DC-input battery charger installed in the trailer, a Redarc BCDC1240.  Then I ran 8G wire to the 7 blade connector in both the trailer and the tow vehicle to reduce voltage drop and increase current carrying capacity.  I installed a 70A circuit breaker in the tow vehicle at the battery (a typical factory wiring setup might have a 30A fuse and 10G or smaller wire).  The battery charger boosts the alternator voltage up to 14.9V and is a real 3-stage charger with boost, absorb and float stages indicated by LEDs.

Unfortunately getting good performance out of your trailer battery is not as simple as connecting a wire to the TV alternator.  It is better than nothing.  But not much better.

lumpy75

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Re: Will my tow vehicle charge my trailer battery?
« Reply #17 on: August 14, 2014, 05:35:21 AM »
Easiest way to check is a VOM/Multimeter at the battery I have a Harbor Freight meter that stays with the trailer. Voltage with vehicle not plugged in, voltage with TV plugged in and engine running should be higher.

You should be able to measure across the battery and find 12 volts when not charge is going in. Then turn on the truck and voltage should go up to around 13.7 volts if it is sending a charge.

rickst29

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Re: Will my tow vehicle charge my trailer battery?
« Reply #18 on: November 11, 2015, 08:11:32 PM »
DEFINITIVE ANSWER:

The Bargeman Supply "+12V" does not normally have sufficient voltage to charge Trailer Batteries. In modern vehicles, including the Tundra, the Alternator contains an electronic controller which adjusts output (Voltage, and therefore Amps) according to the measured "State of Charge" found via the "Sense" wire. For a short time after starting, the voltage WILL be sufficient to charge the batteries - but the "State of Charge" recovers pretty quickly, and the alternator reduces its voltage to a "float" level of 13.5 - 13.8V.

Even if all this voltage could be seen at the Trailer batteries, it's not enough to drive much current - and the batteries will not charge in a reasonable amount of time. But the situation at the Trailer batteries is even worse than that, for two reasons: Voltage Drop in the wiring, and lots of power being consumed by the refrigerator.

Typical RV refrigerators, built using heater-based "absorption" technology, consume 10-15A while running the DC Heater. While the refrigerator tries to draw this power, from both the Trailer batteries and the TV-Bargeman connection, the Voltage at the end of the wiring from the Tundra connection wiring  by amounts which Internet "Voltage Drop Calculators" will estimate for you. "Voltage Drop" values of 5% and higher are not uncommon when the Fridge activates the heater. When the original "13.5V" drops below the Voltage available from the Trailer batteries, the Fridge will pull power from the Batteries instead:

They are being discharged, rather than charged.
- - - - -
The solutions to this problem all involve devices which can consume lots of Power from the Bargeman Connector (even at lower voltage) and convert to higher Output Voltage, capable of charging batteries. Ctek makes (one the "D250S"), and Redarc devices from Australia are very popular for solving this problem. The boxes install in the Trailer, not the TV. You could also build DIY, although multiple boxes would be involved: A Voltage Booster (a 12V->24V "boost" converter, with high current capabilities; A "smart" Solar charger, to convert the Voltage back down (so that the Trailer batteries are charged properly, and not overcharged); and a small pair of "12V" batteries wired in series, in the middle, to stabilize the high-frequency "PWM Mode" square wave demand profile which the Solar Controller will present to the upstream device.

Costs for DIY are (roughly) $60-80 for a nice, weatherproof converter; about $30 for the pair of batteries; and $40-60 for "half decent" Solar Controller. Costs for Ctek and Redarc devices are much higher, but they can also support the use of Solar Panels.
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Alan P

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Re: Will my tow vehicle charge my trailer battery?
« Reply #19 on: March 09, 2017, 03:13:25 PM »
Very helpful info

I am wondering if the following approach would help, at least for those of us with portable refrigerators in our camper.  What about running the fridge from the 12V outlet in the tow vehicle while towing, instead of having the fridge in the camper drawing on the line from the TV and the camper battery.

I also have an AGM battery, and I always leave the fridge plugged in to the camper (while towing).  Maybe putting the fridge in the TV while towing would protect the battery capacity in the camper (while keeping the fridge cold).

Would this approach cause any problems in the TV? 

(I'm guessing we wouldn't want to leave the fridge plugged in to the TV if we stop for a long break, like lunch, however, as it could drain the car battery.)

My camper is small - a teardrop - so the only draw is the fridge, the water pump, running lights, interior lights, and a car stereo and speakers (and whatever we charge from the teardrop battery, such as iPod or iPhone).

Your thoughts are MUCH appreciated.

joelmyer

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  • Joel (W4JNM) and Camille, GA
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Re: Will my tow vehicle charge my trailer battery?
« Reply #20 on: March 19, 2017, 04:18:50 AM »
my 2c worth.

Will it charge? Connect trailer to TV.  Start TV.  Check voltage at battery.  12.6 or less it's not charging.  More than 13 or so it's charging, some.  If it's not charging then maybe it's just a fuse.

When I am going to be camping with no hookups, I carry an extra battery in my truck.  I have a 2nd trailer connector with just the +/- 12 volts connected to the battery.  That's my backup battery that I use with an inverter for fan and entertainment.  And don't run refrig on DC.  It will stay cool enough, or use an ice chest.

Joel
Joel (W4JNM) and Camille, GA

Lou Schneider

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Re: Will my tow vehicle charge my trailer battery?
« Reply #21 on: March 19, 2017, 01:48:01 PM »
If you have a 2-way (120 volt/gas) or 3-way (120 volt/12 volt/gas) refrigerator, the gas mode uses a little 12 volt power to run the circuit board and auto-igniter  but not enough to worry about.  If you have to manually light the flame using a piezo igniter you have mechanical controls and won't use any electricity at all in gas mode.

What you want to avoid is running the fridge in 12 volt mode.  This uses a 12 volt heating element to boil the ammonia mixture and needs a LOT of current.

Leave the refrigerator in gas mode, only use the electric mode when you're hooked up to shore power and you'll be fine.

Boonieman

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Re: Will my tow vehicle charge my trailer battery?
« Reply #22 on: April 04, 2017, 07:09:27 PM »
Just wondering, I used to have an electric fence for the cattle in a remote pasture. I would take a 12 volt battery out there and hook it to the fence charger (it was designed to operate on 12 volts). I bought a cheap solar charger at Tractor supply that I just hooked to the battery posts. It extended the time I had to recharge the battery X 3. I bought another solar charger and hooked it to the battery so I had two of them. Then it would normally last 4 or 5 weeks. Wonder if this would work in this kind of example?
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Jesse Brown

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Re: Will my tow vehicle charge my trailer battery?
« Reply #23 on: May 13, 2017, 09:28:03 PM »
Hi.  This is my first post.  I just bought my first camper and I'm trying to understand the subject of this thread.

My intention is to buy the CTEK D250S to charge my house battery (100 amphour) on the camper from my 2005 tacoma while I'm towing.  Why can't I accomplish the same thing with a much cheaper solar panel charge controller.  They run more in the $30 dollar range, and If I understand how they work, it'll do the same thing as the CTEK.

I know that simply hooking the deep cycle battery directly to the alternator is not the best thing for the battery.  Deep cycles like to be "babyed".  I don't understand what the CTEK will do that the cheaper solar panel controllers won't do.

 

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