Fast charging any lithium ion battery will reduce it’s capacity (EVs and phones). The more you do it, the sooner you will have to replace the battery. Also recommendations are to keep the charge level between 20% and 80% for longest life. Doing that means you actually get 60% of the advertised range.
Probably some truth in that, but I’d be more worried about temperature increases in the battery pack and possible fire hazard situations first. One would hope that the designers have built-in protections and sensors to look for that, but you never know just how close to the edge they operate.
So I’ve been doing it wrong charging my cell phone battery by giving it a full 100% and running down to 1% before recharging again. Will it make any difference with the same battery to switch to the 80% - 20% range now or my battery has already been ‘trained’ to the previously mentioned range ?