2013 D4 Trailer Power Question

[John_D4]

As a start I’m really up on 12v, but I’ve just now had a really confusing conversation about wiring a relay to feed the trailer batteries.

My car setup:

SSB 60ah aux managed by a Projecta idc25x with a permanently mounted solar panel

4b&s wiring from engine bay to tow bar - connected at tow bar but not yet at the battery end.

Trailer:

Currently 2x100ah lead/crystal (cheap Chinese ones that came with the trailer) batteries - will be replaced with lithium when they die.

Redarc manager30, with 4b&s wiring from the draw bar.

Question:

I was going to run the 4b&s wire from the main battery to a Traxxide USI160 and then continuing on to the tow bar (fuses are assumed knowledge). I am not planning on using the switch for the USI160 and instead twisting the black and white wires together and heat shrinking to protect from moisture.

But then things got difficult to understand, additionally in 1 sentence he said that I didn’t need 4b&s and that 6b&s was more than ample, and in the next seemed to congratulate me on using 4b&s wire as it will reduce voltage drop.

Will this all work fine? I get that I have a car with a smart alternator. He kept talking about using the ignition trigger or the rear lighter socket as an ignition trigger on the Manager30. But I’m really not following. Should I have run an additional wire from tow bar to the manager30 in addition to the 4b&s? I know what an ignition trigger is and when I installed the Manager30 I added it to the 4b&s input wire.

Was going to use the USI160 as the controlling relay as it’s on my garage shelf and not being used.

[John_D4]

Here are the stats for the Manager30. It lists DC power unit as between 9-30V so I would have thought that even with the smart alternator that the ignition trigger would be fine leaving it attached to the 12V DV power input cable. https://uploads.tapatalk-cdn.com/20250311/2d7006ea0de3eac3ecfa9bd0f336667d.jpg

[DiscoJeffster]

I guess the question is - do you want the trailer batteries to always be charging when connected to the car, whether the car is running or not? If so, the feed from the car can be the trigger for the Manager30. If however you only want that to charge the trailer if the car is running then you need a trigger wire if you want to automate that.

4b&s will always be better than 6b&s but for 30amps presumably to charge the trailer - as it’s limited by the manager30, it’s also overkill.

[John_D4]

Which Is why I’d thought of using the usi160 to control the trailer feed wire. So, from what I'm now thinking, I could probably do without the relay and go from the main battery to the towbar to the trailer batteries, and connect the Manager30 ignition trigger to the car. This should tell the manager 30 “the car is turned on, time to start work”.

Am I on the right path now?

[John_D4]

What is the easiest way to run a trigger wire back into the car? I have a 7 pin round plug, a 120amp Anderson, and a reversing camera input on the towbar. I've disconnected the white socket.

[Tombie]

John

The manager 30 will not kick in until the trigger wire is energised.
Run 4 B&S from batter to unit, hook trigger wire from the old white socket ignition trigger to the Manager30 trigger wire. This way it will start charging when the vehicle powers up.

If you dont want the unit to go live when no trailer is connected, install a small switch on the trigger wire line in the rear of the vehicle that you switch on when you plug in a trailer

Or if you want to get real fancy - a simple relay using the reed switch on a replacement tow plug, triggering a simple relay from the ignition switchted trigger circuit - so no need to connect anything just hook up and go

[John_D4]

I spoke to a local tow bar install guy the other day about how to run an ignition trigger into the van. He suggested using the red wire from the unused plug (12N?) and splicing that into the blue wire on the standard 7 pin round (which is designated to the fog lights on the trailer). I have never owned a trailer with fog lights, so I did this. This gives me an ignition trigger to the standard trailer plug, and all I’ll have to do is add the other end of the blue wire to the Manager30.

One last question. As the 4b&s is coming straight from the main battery, I can’t see why I’d need to install an ignition triggered relay (ITR) near the battery end. I should be ok with just a fuse and leave out the ITR?

[John_D4]

I’d planned on leaving a note in the trailer battery compartment for any future owner so they know how the ignition trigger was wired