this android external battery used to barely charge my moto x2015

[Naer]

but after like 2 years i get a new phone which had 3,000 more mhn. moto x only had 1800 mhn
my question is did the external battery get stronger or improved by leaving it charged all the time? the android external battery is a anker

 

[Naer]

maybe it's just this new phone is better equiped to be charged by the external battery than the moto x?