I will definitely give those suggestions a try! I've tightened the battery terminal connections, and the battery itself is only about 2 years old. I keep a battery "tender" plugged in through the "cigarette lighter" port in the rear trunk. I unplug it before starting the bike, and it turns over a big sluggishly but does start and run smoothly. If charging the battery, or replacing it would resolve the faults being reported, I'd be very pleased. Thanks for your knowledge and advice!
That doesn't necessarily mean your battery still likely to be in good nick,
especially if it's always been on a tender!! Is it just a basic 'tender' you've been keeping it on, which likely only keeps it at its present state of charge; or a proper tender/maintainer with multiple cycles, including charge, float, de-sulphate, etc?
Broadly, in order to avoid getting bogged down in the technical detail, it sorta goes like this... Unless the battery has been cycled (charged/discharged) fairly regularly (which a good battery tender/maintainers
should do) you may have just killed your battery prematurely thru what you thought was kindness?!
And then when you rode it, how long was that usually for?? Riding for anything less than about 30 minutes wouldn't even put back the charge lost thru starting it, and 'tenders', especially not 'tender/maintainers', aren't really good a 'charging' a battery so much as keeping them at their present state of charge - which, especially with the magneto charge system on the V-twins, wouldn't necessarily be all that great if you'd just done a short ride, and would gradually get worse if you mainly only do short rides.
That said, batteries can still be bad or even just 'not great' from the factory, and if it also wasn't properly charged before installation, it's never going to last long. Then add to that your '
I unplug it before starting the bike, and it turns over a big sluggishly but does start' bit and the likely poor state of charge, it sorta suggests that keeping it on a tender all the time like that likely just hid its poor capability as it gradually got worse over time!! If you're not going to ride your Spyder for an extended period of time and you don't have a good tender/maintainer with those multiple modes to keep your battery in good condition, you're best bet is to disconnect it and leave it disconnected until a day or so before you want to ride next, then give it a good charge, at least 8 hours on a proper charger, not a tender!
So, while it still could be other things, like a dud or sticking relay (they're the big bits in the fuse boxes) everything you've told us so far suggests that you really need to get your battery properly load tested first, and make sure it can maintain 12 volts even under starting load. You can even take the battery out of the bike & take it somewhere to get that done if you need to, still looking for
at least 12 volts, but you won't be able to check the charge system if you do (no real biggie if the battery is dead, but do get it checked once you can start & run the bike!) Only if you do take it out/put it back/install a new battery (properly charged for at least 8 hours before installation, and don't just take the retailer's word for that), be very careful you don't strip/break free that captive nut on the earth under the seat which the pre-2013 Spyders have!!
Good Luck!
) and while you're there, make sure all of your battery terminals and earth connections are tightly secured onto clean, bright metal (just don't strip the captive nut on the earth point under the seat or break the nut out of its captive position! 
