I was curious what my options are for plugging in the ignition fuse slot and/or splicing a wire so that my Renogy DC-DC charge controller will start pulling only from my engine battery to start and charge my auxiliary battery when the car is STARTED. I worry that some fuses will trigger the charge even if I did the “semi-fault start” where you can start the car without your foot on the brake so all the electrics work but the alternator doesn’t feed back to the battery motor.. ..
I understand that I can use the alternator output to trigger this, BUT, if there is a side of the firewall fuse box that I can use, I would much prefer that because of all the wiring I have already gone through firewall.
Below is a diagram of what I am setting up in a Gen.5 Outback with a Group 42 starter battery and a 100Ah lithium iron auxiliary battery.
Alternatively, I could always use an AUX switch to achieve this, but Renogy’s instructions for my DC-DC charger said to find the D+ switch/trigger circuit and use that…? So I’m curious if there are any thoughts on this approach.
I have the USDM manual for my 2017 Outback and can’t find any mention of it for the life of me… maybe someone knows a page number for me to look at?
Any help is very helpful.
Thank you
