I'm with Batman on this charging stuff. Why throw the motorcycle on a charger all the time? I see where charging would be desirable if one goes MONTHS without riding the bike.

I get out and ride at least once every week or two, often a couple times a week. Even in the winter, I usually get out at least once a month. I've never regularly put a bike on a charger.

Unlike cars, motorcycles have no residual battery drain (radio memory, alarms, etc) when they key is off. If your battery can't sit for at least a month or two without needing a charge, you need a new battery.

Norm it acts differently be cause it's only working half as hard ,you have a two cyl. engine ? Only one cyl. is under compression at a time, If it'a 750 the starter is  only working against 375 cc piston compression  at a time.(think about the manually kicking over a 450ccbike as compared to a 900cc Harley)   If you keep charging the battery and it's bad/tired/old,your just masking the problem and it will quit on you anyway !Have it load tested or replace it.

If the charging system is working then the battery is shot or low on a cell or 2. Or even a loose connection at the battery. Buy a good quality AGM battery it's worth it less headaches.

You will have different characteristics because of 2 different battery types. The trickle chargers have a charge curve built in and it changes based on the type and condition of the battery.

No reason to beat yourself over a dead horse.

Norm ,got some bad news ,your bike warranty never covered the battery anyway.If your other bike only had two batteries in 11yrs what makes you think you can't get 3/4 out of the one in your zuk? But then again if you keep over charging it (boiling the hell out of it )you might not.

If you get a new battery from a box store, have it tested before you leave the store. I got a new AGM before, got it home, thought I shorted out my system, only to eventually find it was a dud...after taking it back to the store for a swap.

Before you install it in the bike put it on the charger overnight..

And IF it was fine Before?
Why cook a battery?
Use your volt meter, if it's 12.5, leave it alone.
I Never leave a battery on a charger and go away for more than an hour.

Not everyone has the modern stuff. My six amp charger is thirty five years old. Works great. Made in America, too.