real battery capaticy after 15 month?

[min68]

I have 2015 Leaf used for 15 month 10k+ miles. The battery indicator still shows 12 bars.
However I feel mileage dropped recently, so I did a calculation.
When battery shows 17% remain, I used my 240Vx16A charger to charge till it full overnight. The electrical data from PE&G showed it used about 16kwh. Considering efficiency, about 14KWH goes into battery. So my battery only has 14/0.83=16.9KWH?
Another proof is, my average mileage per kwh shows 5.2 or 5.3 mile/kwh (North CA with good temperature even in winter), and a full charge just gives me total 95~100 miles (right now I drove 50mile from last overnight full charge , and battery remains 49%). This gives me a estimate of 18.6kwh of total battery capacity.
As far as I knew, brand new leaf 2015 should have 24kwh, minus about 10% hidden (to extend battery charge cycle life) = 21.6kwh.
Seems I already lost 3-4.5kwh or up to 20% battery capacity? just about 10k mils. and battery bar is still 12.
Would it possible Nissan changed firmware (I did maintain Sept 2015 and updated firmware) to hide more battery capacity , to better protect battery?

 

[RonDawg]

The most accurate way to find out your actual battery capacity is to purchase a wireless OBDII reader that can connect to a smartphone running an app such as LeafSpy or LeafStat. Which OBDII reader you should get also depends on the smartphone platform.

 

[bbrowncods]

Too many assumptions. Leaf Spy Pro is your answer.
I will say I have a 2014 with 20K miles and 19 months old that has lost about 4% GIDS and Hx since new.