EV drivers will often notice that “fast charging” is typically fairly rapid up until the battery is about 80% charged, after which the charging speed slows down noticeably. This is typically because the vehicle is trying to prevent the battery from overheating, which causes the onboard software system to throttle the charging speed. An overheating battery presents safety concerns and can increase the rate at which the battery pack degrades. Therefore, opting to use “slower” charging options such as Level 2 EVSE over a longer period of time at a home or office to get a vehicle’s charge up to 100% is typically a preferred option for a battery’s long-term health.
References:
https://cyberbackpack.com/blogs/news/why-ev-charging-speed-slows-down-beyond-80