Question Anker Charger Battery Life

[JoeBost67]

I have had an Anker 79AN7917 phone charger for several years but have never really needed to use it. I like to keep it charged for storms/ power outages etc. Like the one coming now...
All I have been doing in charging it up to max once in a while to keep it fully charged. Is that bad for the battery life? Should I drain it and fully charge it at some point?

 

[jojesa]

I have found that charging it up to 75% every time it goes down to around 25%-20% capacity, extends the life of the battery.