Renogy b2b wiring question

[ermracing]

I'm in the process of installing a Renogy 20a b2b charger for my solar batteries. The basic wiring is simple and I have nor problem with where all the wires go. My question deals with the 12v supply line and the switched 12v line. In a normal world, the 12v supply line would be hot all the time and the 12v switched line would be hot when the ignition is on, or possibly on/off with another switch.

In my setup I plan to have the 12v switched line powered by the running lights and then turn power on to the 12v supply when I want to use the b2b charger. Is there any problem if the 12v switched wire is hot but there is no power coming in on the 12v supply line?

Thanks,
Dave

[desrtdog]

I have a 40A Renogy DC-DC charger...I'm a little confused about your terminology - when you refer to the "12v supply line" do you mean the positive input to the charger? (On my parts diagram, this is listed as Key Part #2.)
Regarding the 12v switched line, I believe this is labeled "D+" - correct?

Assuming the above is the case, I am not sure why you would not just control the on-off function by putting a switch in the feed line to the D+ line (rather than tying it into the headlights), and having the positive input always supplying the charger. The charger is set up such that it will not pass power through to the house batteries unless it is 'turned on' by supplying power to the D+ terminal.

My charger is wired this way, where I used an extra switch in the driver's control panel to supply the 12v signal to the D+ terminal. The 12v input and output lines (from the alternator / to the house batteries) have inline isolation breakers, but these are more for overcurrent protection, and not used to switch power on/off.

Post #15 of my build thread (https://www.skoolie.net/forums/f11/t...nic-42584.html) shows a pic of the switch panel, and post #40 is a description of the electrical system. I would tend to avoid having the high amperage line as the one that you use to control power to the charger - if that's in fact what you were asking about.

[ermracing]

Then reason I'm thinking of doing it this way is because my solar batteries and b2b charger are at the rear of my rig, 30' away from my driver seat. I would have to run a wire all the way back to the D+ terminal, which I can do. Also, the 12v input line will be switched anyway since I'm feeding it from the line going to the wheelchair lift, which I have on a switch already and typically do not have on while driving, only parked.

Since I run with my headlights on, the D+ would be hot, but when I wanted to activate the charger, I would flip on the wheelchair lift feed wire, which is fused going to the b2b charger. I just want to make sure I'm not doing any damage to the charger doing it this way.

[desrtdog]

Gotcha. I ran the positive input from the W/C breaker as well, but all my electrical are up front (behind driver's seat) so running the extra D+ wire was no big deal.

What about tying into the 12v input from the W/C line for D+? ... then both are supplied at the same time.

I don't see anything in the instructions that would say you could not do it your way...only concern might be that you get a power surge into the charger when flipping the switch. Might give Renogy tech support a call...

[ermracing]

Originally Posted by desrtdog

Gotcha. I ran the positive input from the W/C breaker as well, but all my electrical are up front (behind driver's seat) so running the extra D+ wire was no big deal.

What about tying into the 12v input from the W/C line for D+? ... then both are supplied at the same time.

I don't see anything in the instructions that would say you could not do it your way...only concern might be that you get a power surge into the charger when flipping the switch. Might give Renogy tech support a call...

Thanks, I will check with them before setting it up this way.

Dave

[More2See]

The circuit will operate like any other until you trigger the switch by turning on your running lights. I have wired a system in exactly the same way before.