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Old March 2nd 17, 04:30 PM posted to alt.comp.os.windows-10,alt.comp.os.windows-8,alt.windows7.general
Ken Springer[_2_]
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Posts: 3,817
Default How to interpret laptop battery results.

On 3/1/17 8:19 PM, Paul wrote:
Ken Springer wrote:
Let's say you run the powercfg command from the command line.

The battery design is 60,000, but the last full charge is 40,000.

Would it be accurate to say the battery has 66% or 2/3rds of it's life
left? Or is some type of sliding scale more accurate, and maybe the
battery has only 40% of it's life left?

Is there an easy to understand web site for this? I'm not sure of what
terms I should search for in this instance.


The term you want is "battery fuel gauge".

http://batteryuniversity.com/learn/a...ery_fuel_gauge

The connector on the laptop battery has room for serial connections,
allowing the CPU to query the battery IC.

The battery capacity declines with age. When Windows says "100% full",
it means 100% of the remaining 60% or original capacity the old battery has.
You check the "hours and minutes remaining", as a means of guesstimating
the Watt-hours the battery actually holds. If you laptop used to say "three
hours" when the battery had just finished charging, maybe now it says
"two hours", under equivalent conditions. Of course, controlling the
conditions on a laptop is notoriously difficult.

Some fuel gauges, if they have not received a calibration cycle,
they count the number of times the battery have been charged,
and estimate the loss in capacity as a result. I'm sure the driver
software in Windows, cleans up any "inconsistent" information
so you won't get a scare like "105% full".

The battery IC is supposed to be "counting coulombs" or some such.
It does that, rather than using open circuit battery voltage
as some sort of indicator. Coulombs should be a better method,
than any voltage-based method.


Hi, Paul,

That's not the type of indicator I was referring to. I'm referring to
the powercfg report available with Windows.

Open a command window.

Navigate to Windows\system32.

Type powercfg -energy -output power.html

It takes a minute or so for a report, power.html, to be created in the
system32 folder. You can use the full pathnames as you desire to end up
with the output file where you would like it as well as change the name
of the report.

Open the file in whatever, search for Battery Information. Those are
the numbers I'm interested in.


The above is for Windows 7. I've read online that for 8 and 10, you
change energy to batteryinformation. I don't have access to an 8 or 10
laptop, so cannot confirm this.
--
Ken
Mac OS X 10.11.6
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