Maximizing battery health - Heat and State of Charge

Toyota has been using lithium now for going on 8 years. I've only heard of two failures. Degradation rates seem to be about as expected or many a little less.

As for cooling, the Prime battery is assembled differently from the regular batteries with the battery divided into five rows with air space between them. And it has two fans to move the air. It actually forces the air between the cells (unlike the regular Prius) and then out through two flapper doors in the car compared to just one in the regular Prius. It may be air cooled, but it's much more serious air cooling than in previous batteries. If you play this video, you can see what I'm describing at about the 23 minute mark.