Are you still observing the behavior in #4?

It might be worthwhile to obtain a voltmeter that plugs into the cigarette lighter port, so you can monitor it on the fly.

 

*4 , yeah when car is running it jumps from 12.2 to 13.8 / 14.0 but never above 14.0

its goes upto 13.8/14 randomly and drops down to 12.2, there is no set pattern.

I do have volmeter plugged into cig lighter and above readings are from that.
when I stop at trafic light idling, some times it sits at 12.2 and some times at 13.8/14.

Also today I noticed when I park my car and lock it, I hear some fan still running in engine bay and it turns off after some time. This happens only some times. like turbo timer

 

#4 That sounds pretty normal. Honda does things weird ways, and it appears that more manufacturers are pushing in this direction. I recently rented a Nissan Altima that would regularly allow the 12V to dip to around 11.8V before it would charge again.

The 12.2-12.3V isn't a huge concern because that's a LOADED voltage where the battery may only be providing a few amps of current where the HV system is supplying the vast majority of it.

Is #1 still happening, 12V battery light on more for than a few seconds after startup?

It was #1 that led me to suspect the battery, i.e., it was so weak that its RESTING voltage would sag to the point that the car registered a problem, but it could bring the 12V battery voltage up to a working range.

Something useful to do:
Tonight, after parking the car, release the hood, or is it the bonnet there?
In the morning (8+ hours after parking), raise hood (bonnet?) and check 12V directly.
This gets a resting voltage without putting any load on the battery (even avoids the dome light). You're looking for something above 12.4V - which is about 70% SoC.

 

That is normal. If the car thinks it is "hot" it runs the fan until it is not, even though it is not running. For those of us who live in hot climates the car does that pretty much all the time.

 

 

I can never rule out that a NEW battery is bad/weak from the beginning, so it might not be a bad idea.

Per messagi #13, Is #1 still happening, 12V battery light on MORE for than a few seconds after startup?

 

Yea, first start of the day it stays on for about 20-30 seconds and goes away.

but after that during a day all fine.
with old battery it was staying on for longer, so defo slight improvement.

 

Replace (-) battery cable, insure the body cable attach point is completely clean and shiny. Confirm (+) cable ring terminal is clean.