A scare when she doesn't fire up

[Xerxes76]

I've been regularly riding my z900 around town on short bursts, coz it's summer and 40+° out here. Bike sat last 2 days, and when I switched on the ignition key today, everything started as normal, even the fuel pump primed as always,  but the moment I pressed the ignition button, there was maybe a micro second of crank and everything went dead. No current, no display, nothing. But when I switched off the key, the immobiliser red light kept flashing as it always does. Checked every single fuse, cleaned with electrical contact cleaner spray cleaned the body earthing connection, but nothing would happen. Checked the battery and it was dead as if it hadn't been used for years. Is this possible for a battery to just go dead or give away all of a sudden ? I always knew the batteries to give some signs of increased crank load, slow cranking and dimming of console lights, etc. Some sign atleast ? But this one just went dead. The battery is between 2.5 & 3 years old. Luckily had a new spare battery, hooked it up and she fired up in half a crank.
Anything I should worry about or have checked? I do not have rodent problems and the bikes been serviced regularly. The bike turns 5 next month with 30k kms.
Any guidance or sharing of similar experience would help me calm my nerves.
Thank you

[3alfa3]

Nothing to worry, it was the Battery.

My Battery died last summer after 2 Years on my 2020 Z900. Battery test confirmed very low current and high internal resistance so i bought new battery (EXIDE AGM, price was very good).
I thought that Z900 would have Yuasa which lasted for Years and Years on my previous Kawasaki Z750, but no, it was not Yuasa that came with new Z900.

[Xerxes76]

 

[mininsx]

Sometimes when they go they go with no or very little warning. I had a battery die on me when I had been on a ride and stopped to get gas and it wouldn't crank. Thankfully I was in town and had a friend come to help me push start the darned thing to get it home. 

[MaverickAus]

Battery for sure, I'd have thrown in a lithium, but that's me.