Not sure how accurate this is, but I read from another post somewhere that the recommendation is to just plug it in every night and charge to 90%. Even if you only go around the block. Again, can't vouch for that, but that's what a Service Center told someone else here in the forums.
It seems like a regular exercising of the battery all around is sort of what keeps things in check. Maybe charge it every night to 90% and then once a month drop it to under 20% and then back up to 100%, where you'd then drive it back to 90% so it doesn't sit at 100. I think that's what I was wanting to come up with - some guidelines for people to follow if they drive only short distances, medium, or large distances every day. Will take some time to get there - the most data/information we share the more information we can base those suggestions on.
Li-Ion batteries don't like extremes, they prefer to sit around 50% most of the time. So keeping them charged at 90% for extended periods is not as good for them as closer to 50%, though it's definitely better than 100% or close to 0%. I did the 90% every night with my P85D's first battery and it degraded faster than the second battery, which followed my habits below:
My charging habits now are to only charge to 80% once or twice a week. I rarely use the car during the week so I let it sit in my garage anywhere between 30% and 70%. Once I need it for longer drives during the weekend, I'll charge it the night before to 80%, sometimes 90% for longer trips, but in either case I make sure it completes the charge only a half hour or an hour before I have to leave.
Once every few months I'll charge to 100% just before starting a long drive, drain it to near 10%, then charge again (sometimes at an SC, sometimes at home after the day-trip is over). My goal with the 100% charge is to rebalance the pack once in a while, and get a more accurate reading from the BMS on battery capacity and health.
Doing all this, I've only lost a little over 1% of my Model 3's battery capacity since I got the car early this year, and I have 10,000 miles on the odometer now. My most recent 100% charge from a month ago showed 306.12 rate miles (RM). Previous 100% charge from August was 308.96 RM, and first two 100% charges earlier this year were exactly 310.00 RM.
My suggestion for those of you who drive your cars more regularly, such as daily commutes, is to charge early morning before going to work and only proportionally to an SoC that is equidistant to 50% based on your commute. For example, if driving to work consumes 35% of your battery, then charge to 85% so when you arrive at work, you'll have about 50% left. The battery will happily sit at that SoC for several hours, then you'll drive it home and get down to 15%. Plug it in at night and have it charge until it reaches 85%, charging at a rate such that you leave for work again the next morning only a few minutes (or up to an hour) after the charge is complete.
Anyway, that's just my 2 cents from driving Teslas for the last 5 years.
