Getting power from Tow Vehicle??

[gdizzle]

I am trying to get the 2017 x17Z ready for my first trip.
I have removed the battery so it doesnt get stolen.
I hooked up the 7 pin connection to the tow vehicle and turned on the car.
I am getting brakes and turn indicators and driving lights, but when I tried to turn on lights or radio or fridge inside, I had no power.


So question is, do I need to have the battery connected in order for my to get power from the tow vehicle? I did test the 7 pin and it is sending 12v from the car.


Ideas?
why do I care? Because I think I want the fridge to run while I am driving.

[Enforcer110]

I would think you need a battery installed, or you will have an open circuit.

[Yooper906]

Originally Posted by gdizzle

I am trying to get the 2017 x17Z ready for my first trip.



Ideas?
why do I care? Because I think I want the fridge to run while I am driving.

Another thing to consider running without a battery, is your electric brakes and breakaway switch.

[Jagiven]

You do not need the battery on board to get your 12V items to work. I would check a few things.

Have a multimeter? If not, I would strongly recommend getting one, it is a great tool for diagnosis work.

Start off with KIS;
By chance have you checked for a blown main fuse. There are two in the power distribution center?
Is the positive battery lead touching the TT frame, and blown a fuse?

Check the wire connections between the 7pin harness and the TT wires. It is well known for the connections to be loose. Historically they are just a wire nut, and not twisted on tight. This connection could be in one of two spots. For some, there is a metal electrical box on the tongue near the front wall. Open it up and check the wire nuts. On my HTT, they drilled a hole through the floor and the connections were behind a wood panel, in the cargo hold.

X2, a functional battery is required for the emergency electric brakes while in transport.

[DocBrown]

Check your state towing laws. Most states require a breakaway kit with an onboard battery to set the brakes.

Why not run the fridge on propane? Alternatively what we found is that for shorter trips, 3-4 hrs the fridge stays plenty cold until it's plugged in again at a CG.

[Jagiven]

Originally Posted by DocBrown

Check your state towing laws. Most states require a breakaway kit with an onboard battery to set the brakes.

Why not run the fridge on propane? Alternatively what we found is that for shorter trips, 3-4 hrs the fridge stays plenty cold until it's plugged in again at a CG.

The propane option still uses 12V for the controls

[DocBrown]

Originally Posted by Jagiven

The propane option still uses 12V for the controls

But if the on board battery is installed as it should be, that's not an issue. It's generally needed legally for the breakaway switch anyway. I just think the OP is reinventing the wheel. I understand the theft concern, but the requirement to have the battery overrides that.

[Yooper906]

Originally Posted by Jagiven

The propane option still uses 12V for the controls

Correct, as far as I know. For the controls, which means he is going to need 12V which also opens the propane gas valve.

[Monk]

It is my understanding that you need the battery hooked up in order for the trailer brake-away switch to work.

I can offer that I have been using 6 frozen freezer packs placed in the fridge the night before I leave, and they cool everything down nicely. Day of departure I place food in the fridge, leaving the packs in place. Once I get to my destination, I put them in the freezer to re-freeze for the trip home (to keep any leftover food fresh). I have not had any issues at all, and this way I don't have to run the fridge the night before or while going down the road.

Hope this helps,
Monk

[Marcm157]

In addition to what others have said about the break away switch needing an on board battery, I don't think you will have enough current from the 12Volt charge wire from the truck to power anything in the camper without a battery...

[Scott91370]

Even if you get 12v more than likely the truck feeding the fridge will not be enough amperage.

[craigav]

I agree with everyone that you will want to have the emergency braking system in place when towing.

However, on my last RV that I took the battery out when in storage the interior lights would not work by simply having the 7-way connector plugged in and the reason was that the power cable from the 7-way connector was connected directly to the battery as well as the power cable feeding the RV. When I took out the battery I was careful to keep the cables isolated but what was needed and what I had to do was to connect all of the 3 (I believe it was 3) positive cables that would have been on the positive battery terminal to each other which I did with a bolt and then taped the bolt and wires up so they couldn't contact anything and short out. After doing that, I was able to simply bring my truck to the RV and plug in the connector and have power to all 12v lights and accessories in the RV.

More information, I created a cable with two alligator clamps and a 7-way female connector so I could easily connect a battery to the RV whenever needed. What I was using was the same battery I was using for my boat trolling motor for a while and I wanted an easy way to use that battery or any other battery as needed. Sometimes I would take my car to check on the RV which didn't even have a 7-way trailer connector but with the cable I made I could simply connect the clamps to the car's battery and plug in the RV to the cable I made.

~CA

[16WhiteColly]

You need to have a battery connected on the trailer, if not, you will cause extra strain on the truck alternator since it is trying to charge the truck and trailer battery when hooked up to the 7 way.

[craigav]

Originally Posted by 16WhiteColly

You need to have a battery connected on the trailer, if not, you will cause extra strain on the truck alternator since it is trying to charge the truck and trailer battery when hooked up to the 7 way.

??? How would the truck alternator charge the trailer battery if there wasn't any trailer battery connected? ~CA

[jeepjeepster]

Originally Posted by Scott91370

Even if you get 12v more than likely the truck feeding the fridge will not be enough amperage.

This. Ive tested mine and the fridge draws more than the little 14awg wire going through the 7pin plug can carry. You’ll have a voltage drop and it will slowly drain the trailer battery (if you have one). They make dc to dc chargers that basically boost up the voltage, but you need the correct size wiring to handle it.

My battery is around half drained after a 4hr trip.

Im not exactly sure why the normal dc items on the trailer wouldn't work if the 7pin is supplying power. If the vehicle is supplying power to the trailer battery, it must do so even it the battery is unhooked. You have something else going on.

[garywilson]

Puzzled.
What is ref power source supposed to be? 120V, Propane + 120V (2 way), or Propane + 120V + 12V (3 way)?

If 3 way, 12V from vehicle is just enough to keep cold, not make cold.

[John7349]

DO NOT TRAVEL WITHOUT YOUR BATTERY INSTALLED!
Bad things can happen. This defeats the emergency trailer braking.

[Levinehikeski]

Power from the battery to 12v items goes directly from the battery to those items (thru a distribution block of some kind). It is a separate circuit (not connected to each other) unless the battery is hooked up, or you connect those wires together that would be together on the corresponding posts of the battery, like already mentioned. Plus, you will have no brakes which is illegal in many if not most states, depending on trailer size.
Don’t try to reinvent the wheel, if you are that worried about a battery… you should be more worried about no brakes.

[jimmoore13]

I see lots of responses. I will likely repeat or contradict some.

My take:

When plugged into SHORE POWER, your converter will feed the 12 volt circuits in the rig...with or without a battery.

When you have a battery onboard, the battery will feed the rig's 12 volt circuits....and/or be charged when hooked to shore power.

When connected to the TV's umbilical, you have power to all the running lights, brakes, and a trickle charge (usually up to about 7 amps or so) to the RV battery.

The umbilical from the TV does NOT feed the 12 volt systems in the rig UNLESS there is a battery in the circuit...and it's the battery feeding the rig's 12 volt loads and the TV umbilical charging the battery. The TV's umbilical DOES NOT back feed the converter...it only feeds the RV battery.

It is ILLEGAL to tow without a battery on the tongue, because it's the rig's battery that will supply power to the emergency braking system should the RV become disconnected from the TV and it's umbilical.

Your solution is very simple. Install the battery you own BEFORE you tow.