Battery Isolator or a 40amp Relay?

[Snorebaby]

I am installing an alarm system and LED lights in my 6x12 cargo trailer. I have a battery for the trailer brakes that gets charged when hooked up to the truck. I don't want to use this battery for the alarm and lights, I am installing another battery inside the trailer just for that. I want to charge the inside battery when it's hooked up to the truck, and only use the inside battery when unhooked. So my question is:

Do I need to install a battery isolator on the trailer? If so, what amperage is acceptable?
Or can I use a 40amp Automotive Relay to isolate the inside battery when disconnected from the truck and when the truck is hooked up, it will charge the inside battery also?

I am towing with the wife's 2013 F-150 right now and will be using the Ranger when Ford comes out with the TBC.

Thanks!

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[Floyd]

I am installing an alarm system and LED lights in my 6x12 cargo trailer. I have a battery for the trailer brakes that gets charged when hooked up to the truck. I don't want to use this battery for the alarm and lights, I am installing another battery inside the trailer just for that. I want to charge the inside battery when it's hooked up to the truck, and only use the inside battery when unhooked. So my question is:

Do I need to install a battery isolator on the trailer? If so, what amperage is acceptable?
Or can I use a 40amp Automotive Relay to isolate the inside battery when disconnected from the truck and when the truck is hooked up, it will charge the inside battery also?

I am towing with the wife's 2013 F-150 right now and will be using the Ranger when Ford comes out with the TBC.

Thanks!

You do not need an Isolator on the trailer.
In fact... if you now have a battery that is a dedicated breakaway battery, you can eliminate it all together and wire your breakaway switch to your new house battery.(BONUS!)
The house battery should be wired to charge from the truck when in transit and wired to a converter or a simple 110V battery charger when in storage.
The house battery will then power all of your onboard accessories. and will also still supply power to your breakaway switch in an emergency should you loose the trailer while in motion.

RV trailers are wired as described above. You will also need automotive quality fuses downstream of the house battery to protect your accessories, whether individual inline fuses or an aftermarket fuse panel with a number of fuses equal to the number of circuits employed.

 

[Snorebaby]

You do not need an Isolator on the trailer.
In fact... if you now have a battery that is a dedicated breakaway battery, you can eliminate it all together and wire your breakaway switch to your new house battery.(BONUS!)
The house battery should be wired to charge from the truck when in transit and wired to a converter or a simple 110V battery charger when in storage.
The house battery will then power all of your onboard accessories. and will also still supply power to your breakaway switch in an emergency should you loose the trailer while in motion.

RV trailers are wired as described above. You will also need automotive quality fuses downstream of the house battery to protect your accessories, whether individual inline fuses or an aftermarket fuse panel with a number of fuses equal to the number of circuits employed.

Thanks @Floyd for the response!
I hadn't thought about that! Even though the house battery is the same as the breakaway battery, I may move it to the inside of the trailer instead of on the tongue where it is now. I had someone break into my trailer this past week and I am now trying to fortify it with an independent alarm system. And it gives me a good excuse to go ahead and add LED lights to the inside. I plan on adding conduit to the exposed wiring past the pigtail of the harness to underneath the trailer. I will put a junction box where the battery is now when I move the battery to the inside. I can leave the wiring "as is" and not add the isolator. The extra batteries I bought will stay charged in the shop and I can easily replace the battery if needed. I will monitor the battery voltage with an LED meter.

Now you got me thinking! I may even use one of the new house batteries in Parallel with the breakaway to have more capacity (both are 5 A/h batteries). I don't use the trailer that much so I can always remove the batteries to charge if needed.

Thanks Again!

 

[Snorebaby]

@Floyd
Finally got it all wired up and installed.

Mounted to the top shelf

The wiring under the cover

The wiring diagram so the mess makes sense

The siren came with the Alarm and I added a small piezo horn for the inside of the trailer and a car horn from Harbor Freight and installed it under the trailer where the siren is installed.

I am gonna add another HF car horn and put it on the inside so whoever thinks they want inside can't disable the alarm and all the horns by just cutting wires on the outside. All my power is located inside the trailer.

Even though the amp draw when armed is only 2mA, I am gonna add a solar charger and mount it on the top of the trailer just to keep the batteries topped off.

This is the view looking in from the side door.

The junction box is located behind the cardboard box at the floor. My containers for my E-track supplies and ratchet straps sit there and will hide the junction box when I am using the trailer.

 

[Noseoil]

We have a 100 watt solar panel & group 27 AGM to power the teardrop trailer, lighting, galley stuff, entertainment (TV, sound bar, Blu Ray, stereo) & the alarm system. It's all wired through a PD4045 panel in the galley, for both the 110v shore power & the 12v systems.

Tamper switch is under the spare tire, siren is tucked inside the rim where you can't see it. The siren is about 1' away from your ear if you try to loosen the spare to steal it while you're laying on your back on the ground with a wrench. Surprise!

 

[Snorebaby]

@Noseoil That looks great! I finally got the solar charger and inside horns installed. I also ran the LED indicator light to the dome vent cover. I will need to get a pic of that and post it. At night it gives a soft blue blinking glow onto the dome. I didn't want to drill a hole in the wall just to mount the LED.

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