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To maximize battery health, keep your car's state of charge between a minimum of 20%-30% and a maximum of 70%-80% and use level 2 charging. Frequent, short charges are better that using a lot of battery before recharging. However, for practical use, it is OK to deviate from these guidelines. EV batteries are built to withstand a wide range of use and conditions.
It's advisable to keep the battery's state of charge (SoC) between 30% and 80% for daily use because that is where battery chemistries are most stable. Since there is more chemical instability at 100% or 0% SoC, or as you get close to it, regularly hitting these limits can accelerate battery degradation.
However, some manufacturers that use LFP batteries, like Tesla, recommend periodic charging to 100% to allow the battery management system to recalibrate. Doing this occasionally will help your car's range estimate stay accurate and will not meaningfully hurt your battery.
Similarly, if you need to use 100% of your car's range, it will not destroy your battery to do so. In the best case, set a charge timer so the battery hits 100% right before you use your car. Leaving it fully charged is worse than charging to 100% then using it.
Home charging is less taxing on your EV battery than DC fast charging, and overnight charging is often cheaper than charging during the day. Overnight charging also allows the vehicle to precondition without depleting the battery, so you can get into a warm (or cool) car for your day.
Although there is limited data on the long term effects of fast charging, high-speed charging does generate more heat, which might negatively impact battery health over time. However, battery management systems seem good at protecting EV batteries from high heat or voltage.
In summary, to maximize your EV's battery health, aim to keep the SoC between 30% and 80% when possible, and limit the use of fast charging.
Sources:
https://www.recurrentauto.com/questions/do-i-need-to-charge-my-tesla-to-80-or-100
https://www.recurrentauto.com/questions/should-you-charge-your-ev-each-night
https://www.recurrentauto.com/research/ev-battery-health-car-dealership
