It's all anecdotal evidence as far as I know but I think it is a well accepted fact that there are several things that are detrimental to Li batteries. Keep in mind that there are different chemistries involved, just between model years of Leafs and of course, Leaf batteries are different than Tesla batteries and are different than laptop or phone batteries etc.
Having said all that, I would say ANY Li battery is degraded by charging it too fast, too low or too high. The BMS will control most of these parameters but the Leaf BMS will let the battery get very close to 100% or 0% charge. 0% charge is less of an issue since if that happens you are stuck somewhere and have bigger problems :mrgreen: Charging to 100% is much easier and more common.
The common wisdom on the board here is that 100% and high battery temps are bad for the Leaf battery. Either one by itself is not good, both of them together are worse. The battery doesn't just explode - thankfully - but whatever chemical changes occur to degrade the battery are increased under these conditions.
So the general advice is to not leave the battery at high state of charge for long periods of time and to avoid 100% charges when the battery is hot, to the extent possible. If you need 100% charge for a long trip, try to time the charging so it hits 100% shortly before you go to minimize the time it is sitting at 100% charge. Also, if the battery is hot, avoid charging over 80% as much as possible. I'd add that is better to keep the battery above 10% charge if you can help it. If it gets below that, try to charge as soon as possible for the same reasons.
