low daily mileage: is the 50% daily limit "guaranteed battery failure" as a local expert claims?
I have a 2021 Model 3 Performance (NCA, ~79 kWh) and drive only 3-5% per day, 3x a week (short trips to the gym). Car sits in a garage plugged in for ~160 hours per week. About once a month I take a longer trip where I charge to 80-100%, discharge almost fully (to 10%), then recharge for the way back and discharge again.
Based on calendar aging research (Keil/Jossen TUM 2016, Werner et al. MDPI 2021, Battery University, and AAKEE's posts on TMC), I've been keeping my daily limit at 50% to minimize high-SoC dwell time. Imbalance via S3XY Knob sits stable around 30 mV.
A local "battery expert" (claims 26 years working with lithium batteries) told me this is "the worst thing I can do" and "guaranteed battery failure, and I should already book an appointment for the Tesla center" because the BMS can't balance at low SoC because it can't see the differences at 50%. His recommendation instead: charge to 80%, let it run down to ~20% over 1-2 weeks of regular use, then plug in and charge back to 80% — repeat. Explicitly NOT daily charging. His analogy: "you wouldn't drive your gas car to the pump every night to add 1-2 liters." When I asked for sources and data, he called Battery University authors "dilettantes who should be institutionalized" and eventually blocked me.
His main technical experience seems to be repairing Lithium packs, and he told me that he is happy to fix my battery once I mess it up with this stupid "50% daily limit" with an "extra charge for being a smartass". His "don't plug in daily" advice also seems to directly contradict the Tesla owner's manual, which explicitly says to leave the car plugged in when not in use.
A lot of the advice I see online tends to agree with the following:
use as low daily charge % as you need to get by for your daily trip without going under 20%. So keep it around 50%.
Keep it plugged in all the time and charge frequently. Low DoD (depth of discharge) is better for the battery long term and will result in less degradation per mile driven vs. higher DoD and less frequent charging.
avoid very low and very high SoC for prolonged periods of time.
So: am I missing something, or is the "80→20% deep cycling, no daily charging" advice basically extrapolated from LFP behavior and old S/X firmware? Anyone with long-term data on low-SoC daily strategy on a 2020+ NCA (or NMC) Tesla?
My goal is to keep degradation to a minimum. I work from home, the car sits in the underground garage, plugged in 24/7 with a 50% daily limit. Can I really mess up my battery this way? I would think that if this would damage the battery long term, Tesla wouldn't allow a 50% limit setting. I'm open to changing my routines if data shows that this is a bad protocol long term, but all research seems to point in the other direction, especially with me doing longer trips around once a month where I charge it up and drain it down.