If you are charging on L1 you could get a 'Kill a Watt' to measure wattage being used during the session.
How does the 'Battery Conditioning' % look on the Leaf page when you are driving it? Is it over active then?
Good luck telling a dealership there is a problem.....
Used '14 2LT w/ DCFC. +69 K miles.
Mostly free charging! Only one LONG visit to the shop....
GM needs Modern Troubleshooting tools for Modern EV's.
3 step Trouble Tree, 2nd guess not covered by warranty and cost $800. 3rd guess fixed the problem.