Welcome to the forum.
Is this a heated garage? Attached or not? Insulated? Just starting it and letting it warm up a bit is risking condensation in your crankcase.
But to your question. A trickle charger will constantly provide a charge at a lesser rate. It may have fried your battery. Get a reputable battery maintainer/tender. It only charges when it senses the voltage drops below a certain level.
What type of battery is it, AGM, lead acid, or lithium? What is the age of it?
When you turn the bike on and flip the run/off switch on, do you hear the fuel pump prime?
I have replaced key fob batteries with new and found that the new one was a dud. Also ensure that it's not in upside down.
Check your bike's battery connections for looseness and or corrosion, both at the battery and on the frame and starter. An AGM battery is sealed and has no way of checking the electrolyte level. You'll have to pull it and have it tested. Lead acid battery, check the electrolyte levels and top off with new electrolyte or distilled water if you are unable to get the electrolyte. Lithium battery, once it has drained there is no way to bring it back to life.
How well a battery has been maintained will determine how long it lasts. A battery, that has been properly maintained and the bike has been used regularly, could last for 5+ years. Usually you can expect 2-3.5 years out of it
The resting voltage should read 12.6 volts. If it's near 12 volts or less, it should be recharged and tested again after it has had time to "rest" for a few hours. Turning on the ignition switch puts a drain on your battery and you won't get a true reading of a resting battery from the bikes volt meter. Use a multimeter to test the battery's voltage while the bike is off and nothing is putting a drain on it.
While under the seat, check the wiring connection to the ecm for corrosion on the pins and sockets. Clean them at the slightest hint of corrosion. Use a good electrical cleaner and a soft bristle brush then allow to dry. Put some dielectric grease on and reassemble. Reason for this is the can-bus systems on our bikes are sensitive to the slightest changes in voltage.
Pop the side cover off and check your fuses. Do the same for them as the ecm.
Another thing that I can think of is the start switch. Have you changed bars or added heated grips since your last successful start? May have pinched a wire or two on reassembly. Or it maybe corroded up and needs to be cleaned or replaced if bad enough.
I mention corrosion a lot because of your proximity to the Atlantic and I don't know how much salt air you receive.
Sure hope these help you out. Let us know how it comes out.
