Well, it happened to me last night - unfortunately.
No 12V, Not a single light working - at dusk fortunately.
Just coming of the highway 2 miles from home - fortunately.
It's scary to drive home very carefully without lights right by police busy with an accident - fortunately.
It turned out all I had to do (2013 S, 15K miles) was re-seat the two big plugs under the seat, under the 12V fusebox. - fortunatly.
I don't know which one did the trick.
I was about to dig deep, get to the DC-DC converter, measure it out.
I had read about the control signal to the DC-DC converter sometimes not coming thru and hoped for the simple bad-contact failure mode and it was! In a 'doesn't hurt to try' I popped them and re-seated, turned on the ignition and presto!
https://zeromanual.com/wiki/Loss_of_12V_PowerBoy I boy was I happy it 'fixed' it.
This machine is NOT designed for (internal) maintenance.
What a pain to get to anything at all.
Just to get the side-shield off you need to blindly get to a 'hidden' 3mm hex by the rear peg mounts.
I had started on removing the (break) side rear peg to get more working space but even that was nasty with a hidden 13mm bolt which I could only give a 1/12 turn each time with a 12-seat box wrench. Everything is 'from behind'. Bah.
Anyway... here is hoping it will not happen again.
Also I was thinking what if this had happened at a worse time, maybe with the DC-DC converter actually broken.
It made me wish there to be a little backup battery. But to run with head-light, brake-lights with would have to deliver more than 5 amps, so a 'normal' motorcycle battery (heavy!) would last only half an hour or so. Still some setup with LiIon, a diode or two and a hefty warning light on activation could give you 5 or 10 minutes to get to a safe spot.
Hein.