Removing 12v battery to charge Leaf

[lorenfb]

Consider installing one of these to monitor your 12V battery; https://antigravitybatteries.com/products/accessories/battery/chargers/bluetooth-tracker-lead-acid/

I can periodically check my Leaf's, parked on the street about 25' away, battery voltage & state of charge from my house.

 

[LeftieBiker]

That looks like a great way to monitor the Leaf's battery. The car could then be run before the voltage gets too low, leaving the current sensor off could speed charging, leading to a tolerable workaround...

 

[arnis]

I got a new battery(Varta lead acid) fitted but two days later I had the same braking problem.

With 100% certainty it is NOT THE battery.
2016 Leaf doesn't have that many 12V battery degradation problems. Plus you had new battery.
It appears that electro-hydraulic brake is not working correctly.
This can also ruin 12V battery as brake booster can wake up the car when it is asleep. That will drain battery.
12.2V is absolutely OK for vehicle start.

Pulsation while driving suggest ABS sensor failure. But brake pedal going down while stationary seems to be booster failure.

Anyway, this should be fixed under warranty. It is not battery issue.