Does TV charge trailer, how?

[polishr]

I have thought my tow vehicle charged my trailer batteries while towing (through the 7-pin connector). Does it?
I have a 2022 Flying Cloud.
When i turn on the TV’s headlights, the running lights illuminate and the backup camera is energized.

If so, then how is it the trailer batteries do not power the lights and camera after disconnecting the 7-pin plug?

I ask because i am doing a lithium battery and solar upgrade AND I do not understand the function of the DIN rail component shown in the photo below. This is the DC busbar box under the FBT bed.

What does this do? The blue wires are from the 7 conductor TV wire.

[vanderwielen]

Originally Posted by polishr

I have thought my tow vehicle charged my trailer batteries while towing (through the 7-pin connector). Does it?
I have a 2022 Flying Cloud.
When i turn on the TV’s headlights, the running lights illuminate and the backup camera is energized.

If so, then how is it the trailer batteries do not power the lights and camera after disconnecting the 7-pin plug?

I ask because i am doing a lithium battery and solar upgrade AND I do not understand the function of the DIN rail component shown in the photo below. This is the DC busbar box under the FBT bed.

What does this do? The blue wires are from the 7 conductor TV wire.

Yes, your TV does charge your trailer, but not with the same circuit the lights use. It's on pin 4. This assumes your TV supplies voltage which in some past Fords and few other TVs required the installation of a relay in the truck. In your photo, which is slightly different from what I'm used to, the two heavier red wires are most likely to and from your converter, one of which is from the battery. The blue wire is probably your brakes and the black wire most likely from the 7 pin. You must not have solar.

[Bill M.]

The TV does provide power to the trailer though the 7 pin connector. But...it does not charge the batteries much on many rigs. The alternator senses the TV battery and reduces voltage when that battery is charged. The long wires to the trailer reduce charge. And with Lithium batteries the voltage may actually flow from the TV to the trailer. If you wish to charge the trailer while towing you need a DC to DC converter in the trailer. You can hook a small one up through the 7 pin. For a larger one you need an added circuit from the TV to the trailer with heavy wire.

[polishr]

Thank you for both of those replies. You are right about what’s on the positive bus bar. But I’m trying to understand what the component in the lower right does. It is mounted on a silver DIN rail and has three blue wires in it. I will be installing a DC – DC charger, but need to understand the present circuit operation.
I will do some further verification of whether the running light circuit is separate from the battery charging circuit.

[Bill M.]

I mis understood your post because on my browser there is no "picture below."

And my trailers are older and I do not know the answer anyway.

[uncle_bob]

Originally Posted by polishr

Thank you for both of those replies. You are right about what’s on the positive bus bar. But I’m trying to understand what the component in the lower right does. It is mounted on a silver DIN rail and has three blue wires in it. I will be installing a DC – DC charger, but need to understand the present circuit operation.
I will do some further verification of whether the running light circuit is separate from the battery charging circuit.

Hi

The running lights, brakes, and signal lights are powered by separate wires on the 7 pin connector. There is another independent wire that supplies charge current. It is not part of those signaling and lighting wires.

All of that wiring returns to ground through a single wire on the 7 pin connector. That is the only point all the sets of wires come together.

To put in a DC/DC converter, you pull that charge wire off of the 12V bus an hook it to the input to the DC/DC. The ground connections on the DC/DC go to the ground bar in the trailer (just like the wire from the 7 pin does). The output of the DC/DC goes to the same point on the 12V bus that the charge wire used to go to.

To work out what various "mystery" bits and piece that don't hook into this stuff do, get on the phone to AS and see what they put in there. I'd *guess* it's fuses for the brakes or lights. That's only a guess.

Bob

[Airkeeper]

Yes, and when on shore power the trailer will charge the TV battery. A few years ago my TV battery died over night, so when I tried to start the TV there was not enough TV battery power. I was able to connect the trailer to the TV and in about 20 minutes the TV started easily.

[Wazbro]

The reason it is called a 7-pin plug or connector is because it has (get this) 7 separate wires connected by 7 separate pins.
https://offroadofficial.com/7-pin-tr...iring-diagram/

[ROBERT CROSS]

'06 2500 8.1L Suburban.

There is/was a fused trailer 12v 10g underhood connection that needed connecting before the AS was connected as an AS should be connected for us while toeing.
POI...When not moving, unplug.
When moving...zip/tie.

Bob
🇺🇸

[vanderwielen]

The DIN mounted terminal blocks are your brake circuits. This is shown in the schematic for your rig. Essentially, this combines the break away switch and the brake feed from your tow vehicle. In every case, with and without a DC to DC convert and during all conversions I've done, you never will need to touch this. Also, your lighting circuit for rig lights and brake lights bypasses this DC box. You'll find butt splices near or around this box with those wires connected.

[JCWDCW]

Originally Posted by Bill M.

The TV does provide power to the trailer though the 7 pin connector. But...it does not charge the batteries much on many rigs. The alternator senses the TV battery and reduces voltage when that battery is charged. The long wires to the trailer reduce charge. And with Lithium batteries the voltage may actually flow from the TV to the trailer. If you wish to charge the trailer while towing you need a DC to DC converter in the trailer. You can hook a small one up through the 7 pin. For a larger one you need an added circuit from the TV to the trailer with heavy wire.

This!!

[JeffKim]

Confirming the black wire is the charging wire. For lithium batteries it's best to either disconnect this (since it does not charge with a lithium profile or lithium could discharge to the TV) or as others have said insert a DC-DC charger that provides a lithium charging profile.

The 10AWG wiring from the 7-pin will support up to a 18A charger (e.g., Victron Orion 18A or Victron Orion XS). It's nice to have when travelling - it will top off the batteries or keep up with a 12V refrigerator and it's pretty easy to wire in. My TV (Audi Q7) has a 15A fuse on the charging wire so I have a Victron XS which I adjusted the charging current to 15A.

If you want more robust DC-DC charging then as others have said you have to run a heavier gauge wire from the TV to a plug then the plug to the DC-DC converter.

[streamboxer]

Yes your TV should be charging your trailer but it won't fully charge the batteries. Resistance is the reason. Your TV charging works to fully charge the vehicle batteries and they are under the hood just inches from the alternator with a big heavy cable running from the alternator to the battery. The trailer is twenty feet away with a small high resistance wire connecting to the vehicle charging system. As the vehicle battery becomes fully charged the system senses increased resistance from the vehicle battery and reduces the charge rate. Think of it this way - it requires less air to inflate an empty balloon than to "top off" a balloon that is nearly full already. Since the alternator cannot detect the charge on the trailer battery separate from the vehicle battery it provides a full charge to vehicle battery and because of the distance and resistance in the line the trailer battery never gets fully charged.

[polishr]

Originally Posted by vanderwielen

The DIN mounted terminal blocks are your brake circuits. This is shown in the schematic for your rig. Essentially, this combines the break away switch and the brake feed from your tow vehicle. In every case, with and without a DC to DC convert and during all conversions I've done, you never will need to touch this. Also, your lighting circuit for rig lights and brake lights bypasses this DC box. You'll find butt splices near or around this box with those wires connected.

Thank you vanderwielen! That makes some good sense. I should leave trailer braking dependent on the brake pin of trailer plug for sure. I need to ensure that breakaway braking still has access to the trailer’s battery bank. And that bank cannot be switched entirely off during towing or there would be no power for breakaway braking.
I will probe the mystery device.

[TomW]

My '2024 Silverado HD, like my 2013 Silverado HD, was capable of charging my Overlander through the 7-pin connector, but Chevrolet left it to me to install a 40-amp fuse to make it work. Since my American Classic stays on shore power when not in use, and I occasionally check battery voltage, I never installed that fuse.

TomW

[waninae39]

you need to use a battery isolator
otherwise the as could reverse power you TV battery with excess voltage

a device like this helps solve the issue

[TomW]

Originally Posted by waninae39

you need to use a battery isolator ...

While I assume my late-model truck has that feature built in, I guess it wouldn't hurt to hit a Chevy forum to verify should I ever choose to install the fuse.

Thanks,
TomW

[vanderwielen]

Originally Posted by polishr

Thank you vanderwielen! That makes some good sense. I should leave trailer braking dependent on the brake pin of trailer plug for sure. I need to ensure that breakaway braking still has access to the trailer’s battery bank. And that bank cannot be switched entirely off during towing or there would be no power for breakaway braking.
I will probe the mystery device.

Exactly, follow that blue wire and it will lead to the break away switch, then the other side of the break away switch returns to the DIN rail and then to the brakes.

[polishr]

I found a very well documented answer to my original post question. Found it on this forum, but only after I did a search using Google Lens using the photograph in my original post. My text searches did not find answers for me. Anyway, here us the post with very helpful documentation. And the short answer us that the DIN rail device does indeed handle the break away braking switch. .
https://www.airforums.com/forums/f37...am-243384.html

[suncoasteng]

Not always......many 7 pin connectors that were added and not part of the factory option may not have a 12V positive feed. Some aftermarket installers charge extra for that wire and the fuse that it needs. That wire usually is connected directly to the battery. Many people may disconnect the fuse to ensure the TT does not drain the TV battery, leaving you unable to start the TV. Buy a test light and check your 7 pin connector