Whether it’s a low battery or a faulty battery, Windows a good job alerting you to laptop battery issues. But how exactly does it detect problems? Read on as we investigate.
Today’s Question & Answer session comes to us courtesy of SuperUser—a subdivision of Stack Exchange, a community-driven grouping of Q&A web sites.
The Question
SuperUser reader Cam Jackson is curious how his Windows 7 laptop knows the battery is going bad:
I have a laptop that’s a little over 5 years old, and I’ve never changed the battery, so I believe Windows 7 when it tells me “there is a problem with your battery”, and to consider replacing it.
My question is: how does it detect a dodgy battery? Does the battery not have the same voltage that it used to?
How indeed?
The Answers
SuperUser contributor Tonny explains:
Laptop batteries have a small chip inside that controls/monitors the charging process and also monitors the number of charge/recharge cycles.
This chip is factory programmed with information how this sort of battery typically degrades over time.
It also can derive information from the charging cycle itself: The time it takes to reach full-charge at a given voltage/current changes when the battery gets worn out.
(Voltage drop during discharge is not reliable as it depends a lot on the amount of current drawn while discharging, so it varies with the use-pattern of the laptop.)
Windows communicates with this chip to get information about the battery health.
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