TV battery and battery bank powering inside lights question?

[BCsteve]

Got a question for the experts. My cargo trailer which I’m converting has inside lights from the factory which are powered by the tow vehicle. I want to be able to power those lights from by battery bank when it’s not connected to the TV. How can I wire this so my battery bank and the TV use the same wiring without the batteries sending power to each other or does it not matter? The easiest way would be to splice my battery bank into the existing wiring. Thoughts, suggestions?

[bdosborn]

You can use either the trailer battery or the tow vehicle battery with a battery isolator:



Here's a cheap one from Amazon:
Amazon Linky

I use a Yandina 100, it's a little more expensive but I've been using it for almost 10 years now.
Yandina Linky
Bruce

[BCsteve]

So this allows the power from the TV to flow through the isolator and to the trailer but the power from the battery bank cannot flow back to the TV? Kind off like a one way valve?

[bdosborn]

More like a voltage controlled switch. The switch closes when the tow vehicle is running and the alternator voltage is over 13V or so, sending power to the trailer battery. When you turn the vehicle off, the voltage drops back down to 12.8V or so and the switch opens and isolates the two batteries.

Bruce

[BCsteve]

I’m a little confused with that diagram. So the black wire (aux power) from my trailer harness, which is currently powering the interior lights, would connect to the isolator. Where would the other side of the isolator connect to?

[troubleScottie]

One could connection the power wire (black?) to the battery in your TD.

However, the gauge is most likely too small for the possible current draw. You would be better off running a separate wire from the TV battery to the isolator to the TD battery with a high gauge -- 6 or less? In this case, when connected, your TV is charging both batteries. You will need some sort of connected between the TV and the TD like an Anderson connector. It would be advisable to run a ground wire also, again the trailer harness common is too small a gauge. Also one should have fuses (2) near the both batteries. Size? at least 40AMP, maybe 100AMP.

The only other issue is that you are charging the TD battery off the alternator. This does work. Some like a staged charger -- there are DC-to-DC chargers out there.

[swoody126]

on my Jeep Cherokee and my F-350 i have 7 pin(flat blade) trailer connectors(factory tow pkgs)

in my cargo trailers the factory lights only work when the TV lights are on

in the 7 pin plug on both my vehicles there is one pin that is hot(12v) when and only when the TV engine is running

this hot pin on the TV charges the trailer battery(s) only when the TV engine is running

my travel trailers over the years have all had the batteries connected to the hot pin on the TV plug which charges them when the TV engine is running

the hot pin on the TV's must have/come with from the factory the aboved mentioned isoator because dead trailer batteries have never drained my TV batteries even when the trailer is plugged into the TV

¿ muddy enough ?

sw

[bdosborn]

My Dodge Ram 2500 has a factory tow package and the 12V pin is always on. Same for my Toyota Tacoma. You need to check your TV and see how it works because there isn't a universal standard.
Bruce

[BCsteve]

My 2018 F150 has the MaxTow package with the 7 pin trailer connector, the black wire is the aux power wire. There’s only power to the aux power wire when the truck is running and the truck senses that the trailer is connected. It is obviously a smaller 14g wire so too small to use to recharge the trailer battery. I’m not thinking about running an additional larger gauge wire for charging at this point. If it’s not easily done, I may just cut the black wire inside the trailer and get the power strictly from the trailer battery, it’s not a big deal. I was hoping that there might be a simple way to wire it so when the trailer is hooked up, the lights would get the power from the truck since it’s already wired that way, when it’s unhooked, it would get power from the trailer battery.

[tony.latham]

...and the 12V pin is always on. Same for my Toyota Tacoma.

Bruce: Is your Taco an antique? My 2007 shut off with the ignition and so does my 2016. Both have the factory tow package.



T

[tony.latham]

It is obviously a smaller 14g wire so too small to use to recharge the trailer battery.

Steve:

Is that 14 gauge wire on the truck side or the trailer side?



T

[bdosborn]

Mines a 2015, but I've only hooked the trailer to it twice. I might have CRS syndrome.
Bruce

[tony.latham]

Mines a 2015, but I've only hooked the trailer to it twice. I might have CRS syndrome.
Bruce

[BCsteve]

It is obviously a smaller 14g wire so too small to use to recharge the trailer battery.

Steve:

Is that 14 gauge wire on the truck side or the trailer side?



T

Trailer side. Even smaller on the truck side.

[tony.latham]

Trailer side. Even smaller on the truck side.

If it were me, I'd run a new wire on both the truck and the trailer. I don't know the wire size on my truck but charging while towing works fairly quickly.

Tony