I'm going to guess that you don't use the kill switch. With your tinkering with electrical mods you probably switched the bike on and off a few times, and each time you did, if the kill switch was in run, the fuel pump came on and pressurized the system. You ended up with a too rich condition for a quick normal start.
Gen II bikes do not typically suffer from the classic hard start issue that Gen I bikes are more known for. In either case, going to 3/4 to full throttle the moment you realize it's not starting will typically allow the bike to fire up. Another good piece of advice is on the first start attempt, keep cranking until it starts.
Understand also, that when you crank the bike and let off, the headlights come on. Unless you switch the key off prior the next attempt, you have less voltage to the starter because the headlights are drawing off battery voltage. That doesn't help the issue.
In both cases you describe, the battery power was fine, the motor turned over, but wouldn't start. It is true that if the voltage gets too low, around 10.8V, the injectors won't fire, so no start. That's not usually the case in what you describe, where it fired up the previous time fine.
Worth noting, its good practice on the Super Ten to not shut it down w/o fully warming it up to ~160F coolant temp. This prevents a false choke situation where it becomes flooded on the next starting attempt.
A battery tender is not a bad idea, but in this case it's more about learning the bike's routine than anything really being wrong.
