Polestar 2 LR owner here. I charge up to 90% as recommended by Polestar and Volvo (same batteries and drivetrains), or to 100% when I think I’ll need the extra range.

Whenever possible I charge at home over night when electricity is cheap-ish. It’s much more convenient (not to mention cheaper) than public chargers, and the slower charging speed compared to fast chargers is better for the battery. With 11kW it would take about seven hours to top up a near-empty battery, though I hardly ever arrive at home with less than 50%.

As a rule of thumb, lithium batteries are the happiest at around 75-80% charge and increasingly unhappy above 85%, so unless you need the extra range, 80-90% is a sensible upper limit. Regenerative braking may also be impacted above 85%, as the braking may produce more energy than the battery can take. Be aware though that a SoC below 15% is much more damaging to the battery than one above 85%.

Having said that, unless you do really bad things to your car on a regular basis, most studies so far have failed to demonstrate a significant difference in battery life attributed to charging behaviour, so whether you charge to 80% or 90%, charge your car once a week or leave it plugged in all night every night etc. probably doesn’t make any difference that would justify the trouble.

I am not yet an EV owner, but I have done some research into this question, it would appear that most brands batteries are actually pretty good with 10-20% degradation in 10 years good. So odds are you won’t charge enough to really affect it. I plan on charging it like I do my phone, so letting it get to 20% after like a few days of driving, then full charge overnight. My understanding is the battery degrades due to actual charge cycles, so constant charging in theory is more strenuous on the battery. I doubt my “optimizations” will result in more than 2 or 3 % better battery performance, if that.