charging

Up for sale is 13" Apple Mac Book Pro MUHP2HN/A (A2159: i5 8th Gen/8GB/256GB SSD) for parts. It was bought in Oct'2019. Worked flawlessly till last month, however, it has refused to charge since then. Was being used by my father. Dropped at Apple service center, buggers charged 3000/- to tell...

As the title says, how many do it, and how many follow 30-80% as per those battery sciences. I tried this on my secondary phone(Nokia 7+), barely used it and still battery capacity degraded to 73% within 3 years(a lot since I hardly used it). My Dad's phone(Infinix Note 5)has been used roughly...