How, in a year and a half is my MacBook Pro battery only have 85% capacity?
How, in a year and a half is my MacBook Pro battery only have 85% capacity? Not even half the charging cycles.
There are no guarantees regarding battery performance. There is only a rated performance (1000 cycles to an expected 80% battery health). However, if you have it drop under 80% within the warranty or an AppleCare extended warranty period before it reaches 1000 cycles, it would be covered as a "defect".