Those websites go by estimates and info from the manufacturers themselves and the physics of the device. But they are counting by charge cycle but extrapolating the duration. Of course since the estimates are based on charge cycles not actual time, there will be variation between people.
For example, a run down from 100 to 5 is expected to have approx 700 charge cycles before it degrades to about 80% capacity (although Samsung batteries circa 2017 claims to have increased this to 99-95% after that numner of cycles) on for modern batteries. For a person that uses 1 charge cycle per day, that translates to 700 days. But for a person like my mom who charges only once every 3 days, that blows up to 2100 days or 6 years before you even begin to feel minor battery degradation.
Originally Posted by
NexusGirlX I even have a Note 4 that still works today along with the original battery PLUS a battery I bought to go along with it direct from Samsung. These two original batteries still provide an amazingly long charge on my Note 4 and I've consistently run them down to 5% and charged them to 100%. The phone never shuts down early as is the case for many people who have old batteries on their Note 4 phones.
All these so called expert battery care websites can insist that their ways are correct and this and that but the way that I've used the batteries in my phones speaks for itself. I've never seen any evidence that using the battery down to 5% and charging to 100% each and every time will harm the battery. My evidence shows otherwise. It's real life experience that matters and not what some website shows.