Wiring for trailer power

[Karoosafari]

Hi everyone,

I'm installing a power feed to the back of the vehicle to supply power to an off-road trailer via Brad Harrison connector. I need to find the best place to connect the positive feed from?"

I've read that it is better to take it straight from the alternator rather than from the battery positive. So I noticed in the 2010 D4D engine bay that the alternator feed comes into a little device on the passenger side, and then out again to the battery positive.

What is this unit, and can I take it from here? If so, which side - input or output side?

Your help on this and any other advice will be highly appreciated?

Many thanks

[CasKru]

My guess is that would be your main fuse and if so, after it.

[ChrisF]

Cassie wont it be better to run it with a separate fuse ? In case of a short you dont want the whole vehicle to loose power ....

[CasKru]

Cassie wont it be better to run it with a separate fuse ? In case of a short you dont want the whole vehicle to loose power ....

True... sorry was just answering the question straight up. You have to have it fused but it would be better to run it of a separate fuse as close as possible to the power source

[Karoosafari]

Thanks for your help thus far guys. Turns out that what I was seeing is actually a solenoid which was installed by the previous owner. So I guess now the question is which side of the solenoid do I tap the auxilliary power from - alternator side, or battery side?

[CasKru]

I would install it alternator side with a fuse of course

[ChrisF]

what are you doing with the power in the trailer? 2nd battery?

How are you going to charge this 2nd battery?

DC-DC charger or from the alternator?

You might just want to use that solenoid to isolate the second battery from the vehicles primary battery .... BUT, a lot of questions needs answering before one can correclty choose which side of the solenoid to use. (dont even know the rating of the solenoid, nor the wire size supplying it ....)

bit difficult answering this with so little info.

[Karoosafari]

Hi Chris,
Yes, I want to provide sufficient power to the off-road trailer to charge a deep cycle battery. I will be using thick 8mm core powercables. The feed will be fused in two places (Car and Trailer). I only need this power whilst the engine is running, hence wanting to trun it direct from the alternator. But this is as much as I know - electronics is not my strength I'm afraid!!!

So if I understand you correctly, the best place is on the alternator side of the existing solenoid?