18650 mod box charging socket

I was looking up charging circuit in the ECF and your blog came up and i thought i could help. I am not 100% sure of my method, it seems to work well, I will try to attach pictures as well. This was done on a self-made 14500 box mod, lets forget about the other wiring a moment, the green wire is positive, pink is negative. I believe the diagram speaks for itself.
The voltage in pin is soldered to a wire which is soldered to the positive contact by the master switch, the power out pin is soldered to a wire to the negative part of battery connecter, or to the negative battery connector tab. Placement of your electronics may differ, also with an 18650 you have a lot more room in a case. This will also turn your PV into a passthrough at 5.1 volts (at least here in the states)
I'm not sure if you need this thorough an explanation, just want to be helpful, I used a multi-meter to determine polarity on the usb port once I connected it to a live cable. Usually you want to use the two outside pins ( I take the other pins for ease ). The cheapest way I found to get the USB piece you need is to buy a Mini(female) to Micro USB adapter, pry the casing, de-solder the wires, connect appropriately, and voila. I cut out a space for the USP port and epoxied it in there, works great. I buy the adapters off of amazon, usually less than a dollar a piece. here is a pic of the wiring, hope that helps.