When I first fully charged my 2019 Kona, it gave a range of 307 miles. After a couple of months it was 273 after a full charge. Now I've had it 6 months and the range is 256. At this rate I'll be under 200 miles before one year.
I've found it to be pretty accurate. Weather, and the type of driving you do, are the biggest factors affecting your range. Don't worry it will go back up when the weather warms up, if you keep do the same type of driving! I do a lot of highway driving and have much lower range than the city drivers on here.
The actual original range advertised was 258 miles. https://www.theverge.com/2018/12/17/18144959/hyundai-kona-ev-electric-suv-range-price I would not be concerned as the BMS is doing it's job. (driving conditions etc) If there were a problem of degradation with a cell or group, the first indication would probably be a sudden loss of usual range or a premature turtle. No reports yet on negative Kona EV pack degradation but there are ways to check this if you are inclined: https://insideevsforum.com/community/index.php?threads/torque-pro-on-the-kona-overview-and-setup-for-interested-owners.6970/
Thanks. My phone has an app that scans the battery, cell by cell, and fixes those that are erroneously labeled as not working. Every time I do it, a few are fixed. Sure wish there was something like that for my car battery.
I was getting almost 330 miles on my GOM in the summer (leased my Limited last May). Down to 296 here in the chilly San Diego winter.
My range fluctuates depending on driving habits. I just finished 350 miles of highway driving at 70 to 80 mph and my 80% range is down to 234 miles at 80%. I week ago, I was at 264 mile range at 80%. One week of commuting and local driving will get me back to over 255 miles at 80%. Here in Florida, we have no really cold weather, so heater use is usually not needed.