... I've been unable to find a detailed explanation from Tesla as to how best to maintain battery health. .
Perhaps it's just the geek in me that wants to know the details and reasoning....
First, I do not claim to be an expert on li-ion chemistry or performance. Second, I really have wanted to know. Third, I have had a very specific interest in that I had an airplane which had a li-ion that had a thermal runaway and subsequently was retrofitted with a ni-cad.
So, when the NTSB had hearings about the Boeing 787 battery woes i trundled off to Washington, DC for a couple of days listening to engineers, physicists and industry people discussion battery chemistry, cell sizes, fault causes, quality control, charging controllers and health management, among other things. I learned an enormous amount, not least from the tesla head of battery QC, who was the only person in the room who seemed to have herself completely in command of the facts.
Therefore I have formed a few opinions, which I think are well informed. Among them are:
1. Regardless of specific chemistry battery manufacturing quality control is more important than most other topics;
2. Testing, testing, documentation and monitoring are necessary at cell level. Only Tesla was doing all that at the time of the NTSB hearings.
3. Charging and discharging procedures, including load balancing should be complexity automated because manual processes will not be reliable; people will misuse the batteries.
The net of those things was that Tesla had designed the production, quality control and battery management to minimise as many problems as possible. Thus, all the lessons that we all have heard about, including daily charge management advice, are predicated on much less capable systems than we have in our cars. Most of the advice we get, including form many Tesla employees, reflected old historical wisdom, but not the state of our own vehicles.
By definition daily 100% charging can shorten battery life, just as regular operation below 10% will do so. That said, tesla systems do protect from overcharging and Tesla heat management protects from excessive rate of charge, which is why we hear our battery fans operating while Supercharging. Low state of charge is riskier simply because we might run out of juice, although "bricking" in Tesla is not easy to do. So, all of us are obsessing about what, in practice, is fairly marginal for our cars.
I believe that but I still will not go below 20% except in rare situations and I will not go above 90% unless i will use the car immediately after charging to that level.
We can all be assured that were it not for all those built-in protections that we have battery management would be a bigger problem for us than it is.
Some other EV's do have good battery management, some don't. If it is a problem for your EV in hot weather you may be assured that thermal management in your vehicle is inadequate for normal fast charging, so fast chargers from your manufacturer probably have heat management issues themselves. Nissan CHAdeMO anybody?
A few others use such modest battery packs that these issues are less serious and/or use fairly low powered chargers. In any of those situations we can be assured that battery life span and power management issues are far more critical than they are for us.
All this represents my opinion rather than guaranteed fact. I hope it is accurate and I think it is, but I am not an electrical engineer, chemist nor a physicist.
One thing is clear, Tesla got it right. NASA, US Navy, Boeing and myriad others did not get it right. The net result is that we users get to debate optimal battery management without worrying ourselves unduly about thermal runaway, bricking and other catastrophic events. That is probably why Tesla replaces battery packs with anomalies ratehr than repair them in the field. Their paranoia keep us happy and safe!
