Isn't one "recharge cycle" a full discharge / recharge? So charging from 68% to 75% at work would just be 7% of a cycle, and about the same amount of wear as if you'd skipped that top up and just fully charged at home.

With a battery how fast you charge it, how "full" you charge it to, how deeply you discharge it, the temperature at which you keep it, etc., all affect the degradation rate of the battery. So, because charging a battery from 68-75% is better on the battery than charging from 93-100%, storing the battery full is worse, etc., it isn't necessarily true that "7% charging is the same as 7% charging".

> People charge at work from 68% to 75% because is convenient.

Isn't that almost the best possible way to charge a Li-Ion battery?

It is.

I mean, keeping it closer to 50% might be better, but the returns are so diminished by that point that it's a rounding error of a rounding error.

I keep my limit to 75% unless I have a long drive planned, and nearly all my charging at home. I'll probably have <5% degradation after 100,000 miles.