Battery power of MBP 2010 17" suddenly dropped from 30-40% to about 15%

[hajime]

It has happened a few times that the battery of my MBP 2010 17" suddenly dropped from about 30-40% to about 15%. Does that mean the battery will die pretty soon? How many more months will it last?

 

[zarathu]

Don't believe your battery meter. They are notorious for lying to us. They are like the temperature gauge in my car. It lies.

https://marco.org/2009/09/24/laptop-battery-myths

 

[ZapNZs]

I agree with Zarathu. Battery meters have certain limitations when it comes to what they tell us.

Do you know how many cycles are on your current battery?
Have you seen a drastic change in the length of run time a full charge provides you?
Have you recently upgraded the operating system?