I know lots of people have done a cigarette lighter/usb plug install using various methods, I did mine yesterday after a long ride and was well pleased with how it came together. I forgot to take pics about halfway through, but I think you can get the gist.
For a little background, I originally wanted to do powerlet, but then considering all the costs to get what I wanted (and I really wanted both 12v and usb 5v), it was going to be unnecessarily expensive. I looked at threads here about using the relay and such, and decided I didn't like that either, not enough candy for a nickel. This fix includes no splices, damages no wires, and is fully reversible.
I did some poking around, and this is the final product.
2x female blade-style connectors
2x male blade-style connectors
Heat shrink tubing
Small torch for solder/heat shrink
Drill with forstner bit for hole and a burr to slightly enlarge,
Pocket knife to clean the hole.
First, I bought this guy on Amazon.
Note that it has two, blade style male connectors on the back.
This is just a 12v, marine grade cigarette lighter adapter, but it comes with a 5v, 2.1A USB adapter that pops into the socket and then twists to mechanically lock. I really wanted 3.1A+ total, but 2.1A will be ok. The downside of this design is that the waterproof cap won't engage with the USB adapter plugged in, but it's not difficult to remove and my bike is stored under a roof.
Next, I was trying to decide what 12V, switched source to use for power. Didn't want to use headlight, not a ton of other options up there, so I decided to fiddle with the relay plug and see how it's wired. Turns out that it's a 4 socket, blade type connector receiver that uses 2 plugs to engage/disengage the relay and 2 plugs to supply switched power. "Switched" means in this case that it's only energized when the bike is turned on, which is what I wanted.
What this means is that the power portion of the plug is on whenever the ignition is energized, the relay portion isn't strictly necessary unless you want to use the pretty dongle you buy from Kawi for $40.
If you look at the socket front-on, the left top and bottom are relay and the right top and bottom are power, top is positive, bottom is neutral. Note that the clip is on the BOTTOM. Here's a picture with multimeter prongs present to make it more obvious:
Again, all that are inside that receiver are blade style, female connectors. I happen to have a handy electronics tool box with plenty of MALE blade style connectors and some other good tricks.
I didn't want to rely on a crimp for a vibrating connection, so I pulled off the sheathing and crimped then soldered then folded the blade connectors to the wire. I only had red and green, sorry no black this time. Then I did two layers of heatshrink to protect the connection further. I did two, here's a pic of one:
Now it's just a matter of plugging them into their respective slots and wiring up the adapter. A tighter mechanical connection would be smart, probably, but if it's an issue I've got electrical tape. Blades hold tight though, and there's no tension on the them. Pic:
Now we rinse/repeat on the other end of the wire with FEMALE blade connectors, and we're almost done. I recommend buying fully insulated ones. I accidentally bought male insulated connectors, so mine got a tiny bit of tape instead. It touches the socket too, to help form a tighter, vibration proof bond. I also slightly squeezed the female connectors to ensure snug fit.
Now I drill and clean the hole for the plug, note that in this build I am NOT using the backplate, just the rear tension nut. No pics of this. Because it's a full depth 12v adapter, be wary of the turn signal stem if you try this.
Happily, because the position of the gauge cluster doesn't move relative to the relay plug, we don't have to accommodate the swing of the yoke for the install, just make sure it's clear of moving parts. Easily done. Then slip on the tension nut, plug in the female wire connectors to the male blades on the back of the socket, and then tighten in down, and done.
Even fiddling with the original layout for a while, this took about 30 minutes to complete, at the outside. Fast charge works fast on the phone and if I need to plug in the camera, I can do that too. I will put some dielectric grease inside the usb ports as well. The usb cord is a little fiddly, but I'll probably buy a shorter one and be set. I can take a pic with the phone in the mount and plugged in, if anyone wants to see.
Total cost: $10 for socket, plus bits and pieces laying around. If you had to buy all the connectors and wire, add about $5.