Where did this 80% figure come into play ?
First, recall that all batteries degrade with time. Then again, nothing is eternal — but, if you just put an electronic device in a vault and never touch it, the battery will stop working long before anything else.
Second, it’s well established that this degradation happens faster and slower under various conditions.
Among most modern battery designs today, the battery will degrade fastest when it is held at a high state of charge at high temperature, most especially if it is charged quickly when hot for that last few percent.
Again, this is all well-established physics and chemistry.
There are undoubtedly circumstances in which it’s more important to quickly cram as much juice into a battery as possible, never mind the adverse consequences.
But there are also undoubtedly many more circumstances in which you truly gain absolutely nothing whatsoever by doing so.
We have both a Chevy Bolt and an old (second-revision, I think) Nissan Leaf. And both are parked outside, on the driveway … in a suburb of Phoenix, Arizona. Where overnight temperatures don’t fall below 90°F for a few months of the year, and ambient daytime high temperatures can hit 120°F — in the shade, and the driveway is in full sun.
So, of course, I limit charging on both cars to 80%. And I keep the Bolt plugged in whenever possible, too, since it has a battery cooler that it’ll automatically run when it needs to when the car is plugged in.
And, you know what?
I have not once, never ever, been stranded by not having enough range in either vehicle.
The Bolt, every morning, has well over 200 miles range, far more than we’ll ever drive in a single day save as part of a road trip.
And I know that the Leaf can’t make it to the other side of town and back, so I don’t try; however, it’s absolutely perfect for the daily commute plus groceries plus all other random errands, even limited to 80% of its already meager age-depleted range. With the (surprisingly good) A/C blasting at maximum, even.
Hope that helps you understand just one of the many real-world scenarios in which people choose to limit the maximum charge.
And, regarding the Ultra? Just as the Bolt starts every day with waaaaaaay more range than we ever need, even when “only” charged to 80% the Ultra starts every day with waaaaay more more charge than I ever need, even when “only” charged to 80%. So I certainly have nothing to lose by limiting the charge to 80%. And since I may well gain a few years of extra life out of the watch by doing so … why not?
b&
