Thread: Trailer socket ignition on/off pin for Enerdrive DCDC

Getting closer. Found the plug in the rear cubby that is attached to the 12s socket. It has 2 wires connected to it only. One is the always on 12v (working) and the other is the ignition switched wire. I confirmed this by putting 12v on the ignition switch socket entry and pin 6 on the 12s socket now shows 12v. I then temporarily put the accessory socket 12v feed (which I know is switched with ignition) on the plug and pin 6 is now active when the car is on and switches off when the car is shutdown.

Fuse 54 had power so I can eliminate the fuse as the issue (unless that is not the right fuse). The plug to the socket is also OK.
Probably 2 options left now.. Wiring to the plug is not working which is probably unlikely. The relay that is involved is faulty is more likely. Just cant figure out now where that relay is.

In the interim, I can bridge the accessory socket to that plug as a workaround.

I've just re-checked the diagram, and relay R273/252 is switched by a FET in the CJB labeled "engine run". Silly question, but is the engine actually running when you do these tests?

Edit: Also, the relay is plugged into something connected to C2937. The location diagram shows that in the rear corner of the car. It looks like a dual relay unit with one for the trailer feed and the other for the rear wiper.

The engine is definitely running. I didnt realise that wiring diagram showed wire length so that is most useful now I can see that. The relay looks to be around 2m from trailer socket if Im reading it correctly so I'm thinking that relay will in the LH panel closer to back seat rather than the rear cubby hole. I've been in that section before on my old D3. I think it was the reverse sensor ECB I replaced at the time. Was quite a while ago though. Thanks again.

Originally Posted by Ashes

The engine is definitely running. I didnt realise that wiring diagram showed wire length so that is most useful now I can see that. The relay looks to be around 2m from trailer socket if Im reading it correctly so I'm thinking that relay will in the LH panel closer to back seat rather than the rear cubby hole. I've been in that section before on my old D3. I think it was the reverse sensor ECB I replaced at the time. Was quite a while ago though. Thanks again.

Have you got the connector location diagram?
LR4_CONNECTOR_QUICK_REFERENCE_GUIDE_(1a).pdf

No I haven’t!! That is an awesome diagram coupled with that other wiring reference. Thanks heaps.

Btw…the issue I’m really trying to solve is to isolate my car batteries (traxide isolater) from my large lithium battery in the caravan. I didn’t want the DC2DC drawing those down when the engine was running. I was going to do that via a ignition controlled relay.

I asked enerdrive the question today and got this response regarding what I’m trying to do.

“The Ignition Sense terminal is only to be used if the DC2DC is powered off the start battery AND the vehicle has a smart alternator.
As yours is off the aux battery you don’t have to connect the Ign Sense terminal.
If the Ign sense terminal is not used, the DC2DC has a built-in VSR to cut off power from the source (in your case the aux battery) when it sees the source go below 12.8V - thus it won't allow the lithiums to suck the aux flat so no need to disconnect the Andersons.

Now having said all the above, we prefer DC2DCs to be powered off the start battery to ensure the alternator is feeding the battery whilst the DC2DC is drawing from it. Accordingly one then needs to power the Ignition Sense terminal properly if it is in a smart alternator type vehicle”.


So by the sounds of it…just plug in the Enerdrive DC2DC and it will stop charging when the source is at 12.8v which I guess is pretty much 100% SOC on 12v AGM’s.

Enerdrive DC2DC is definitely shutting down when the car ignition is off as there is less than 12.8v being presented to it. No need for a relay to cut power in my installation. Also pumping 40A into the lithium battery when the car is on so looks to work well with 6B&S from the aux battery in the car to the charger in the caravan. Haven’t quite tracked that relay in the car down yet but not really a priority now. Will get round to it when I can now.

Originally Posted by Ashes

so looks to work well with 6B&S from the aux battery in the car to the charger in the caravan.

It will work even better with the correct size cable, 6B&S is too small for the Enerdrive to work efficiently. Check the Enerdrive manual they recommend 25-50mm2 for a cable length over 5 meters when set to 40A, and a cable size of 35-50mm2 if set to 50A. Both options need a 70A fuse protecting the cable feeding the Enerdrive a 60A at the lithium battery.

I couldn't see it stated anywhere so if mentioned please ignore. The ignition wire on the 12s plug is only active when
the trailer is sensed by the car. This is when the trailer indicator shows on the dash when indicating.