Try to not let the batteries sit for more than one day above 80% charged.
If you need the full range don't hesitate to charge to 100%

Try to not let the batteries drain below 20%.
They're not like the old nickel-cadmium that benefited from deep discharge.

Avoid fast charging in hot weather.

 

If you are going to run the car as a hybrid and engage the ICE, the batteries must drain below 20%; if you keep the battery above 20% by recharging frequently, the engine will never run except when the heater is on or when the computer tells it to do so, like when it had been sitting for a month unused while we were gone, and the ICE engaged when it needed lubrication. As far as reaching 100% charge which it inevitably does with each charging session, there is no option for cutting off the charge at 80% which, I think, the Hyundai engineers would have added if that was important.

 

When I purchased our PHEV, I had the same thoughts. So I did some research and found the "Battery University." If you have time and a coffee at the ready, it should answer your questions. Especially the section on:
How To Prolong Battery Life

Battery University Homepage

Battery University™ is a free educational website offering hands-on battery information.

batteryuniversity.com

 

If you're looking to save money, check with your power company. Many offer cheaper rates at certain times of the night. There's money to be saved by charging then.

 

Does myHyundai app not show the charging rate (kwh)? It is blank in my app.