This assumes the battery percentage displayed is the SOC. This might be the case for laptops or small appliances where manufacturers are happy to trade long battery longevity for a small gain in time to empty, but the Model S for example has gap of a kWh+ and will simply not charge or discharge the battery fully, to avoid these cases where a very low of very high SOC damages the battery.
Correct. I, of course, am talking about battery cells, and not battery systems. It is up to the reader to understand the specifics of their use-case and apply this information appropriately.
