Hi there,
Just to add some input, I had a very similar occurrence the other year when I was out in the middle of nowhere (we get a lot of that in Aus) my battery went flat as I was riding.
Managed to get a jump start from a mine site vehicle (they were some BIG jumper cables!) and got close to home.
long story short, I came back the next day with a new fully charged battery, and the old one that I recharged and managed to get the bike the remaining 35 KM home on a fully charged battery.
Now, I didn't pull the fuse for the lights but that would have got me a bit further if I had. So I would say that, on balance, if you disable the headlights (as they draw a large amount of power) then you should be able to make it the 50 KM home on a fully charged battery, so long as you don't have to stop and restart the bike.
The issue with my bike was a fried stator, which I had to get rewound. Apparently this is not an uncommon problem with 650's. I diagnosed it by checking the AC voltage output from the 3 yellow wires from the stator with the engine running.
It was also evident when I removed the stator cover that the windings had shorted to earth as it had a few of the coils blackened and stank!
Good luck with the fix and keep us all updated.