Battery capacity lower than 42,000 mWh

[ihaveabu]

I just ran a powercfg /batteryreport and the results show:

DESIGN CAPACITY 42,002 mWh
FULL CHARGE CAPACITY 40,567 mWh
CYCLE COUNT 23


is this normal? Seems I've lost 5% of my battery capacity over the last month. It also counts 23 cycles. I know I have not drained my SP2 down to 0% battery before. Where does the battery typically count a full cycle?

I was under the impression that most laptop batteries will drop down to 80% their design capacity after around 300 cycles. That's 20% loss after 300 cycles, not 5% loss after 23 cycles...

 

[ihaveabu]

Battery capacity history
Charge capacity history of the system's batteries
PERIOD FULL CHARGE CAPACITY DESIGN CAPACITY
2013-11-27 - 2013-12-04 42,223 mWh 42,002 mWh
2013-12-04 - 2013-12-11 42,065 mWh 42,002 mWh
2013-12-11 - 2013-12-18 42,005 mWh 42,002 mWh
2013-12-18 - 2013-12-25 41,046 mWh 42,002 mWh
2013-12-25 - 2014-01-01 38,568 mWh 42,002 mWh
2014-01-01 - 2014-01-08 33,192 mWh 42,002 mWh
2014-01-09 34,062 mWh 42,002 mWh
2014-01-10 38,086 mWh 42,002 mWh
2014-01-11 36,554 mWh 42,002 mWh
2014-01-12 31,223 mWh 42,002 mWh
2014-01-13 40,746 mWh 42,002 mWh
2014-01-14 41,026 mWh 42,002 mWh
2014-01-15 36,810 mWh 42,002 mWh
2014-01-16 33,160 mWh 42,002 mWh
2014-01-17 40,467 mWh 42,002 mWh
2014-01-18 39,446 mWh 42,002 mWh
2014-01-19 38,576 mWh 42,002 mWh
2014-01-20 38,711 mWh 42,002 mWh
2014-01-21 40,500 mWh 42,002 mWh


So basically my battery capacity died after the 12/18 update. This is just silly

 

[supersss]

Same for me too... from 42.080 to 40.400 in just two weeks...

 

[Joypat]

I'm down to 40.071 mWh after 61 cycles.

Not sure what a normal drop in battery capacity is after a couple of months of use.

 

[girarcat]

Same here. Every time I perform a battery test, it shows a different capacity. Sometimes it shows 40.000 mWh, sometimes 38.000 mWh...

 

[Zkyevolved]

Installed batteries

Information about each currently installed battery




BATTERY 1
MANUFACTURER LGC_LGC
CHEMISTRY LION
DESIGN CAPACITY 42,002 mWh

FULL CHARGE CAPACITY 41,914 mWh
CYCLE COUNT 11

Here's my information just in case someone is interested. I think it's doing pretty well.

 

[Ruffles]

I don't think this information is accurate. Mine fluctuates constantly. Sometimes, it's 8%, other times it's 5%. I have a friend who's Sony ultrabook has always said 0% and he's had his for almost a year.

I think this is a case of a little information being a bad thing. The fact that the powrcfg utility is a command line program that is somewhat hidden indicates to me that it's not intended for general use. I don't know what the history is behind it but it's probably some legacy developer/debugging tool that has just been left in because other information it provides like charge/discharge times etc. are more useful. There are lots of little programs in windows like that.

The real test would be if you are noticing an actual decrease in battery life AND that decrease can not be attributed to new/different software/background processes. In my case, I have not noticed any change in battery life even though the "wear" indicator sometimes shows as much as 11%.

 

[Sihaz]

Just checked mine and the charged level is generally a bit higher than the capacity

 

[Philtastic]

I've been monitoring my battery after installing the Jan. 18 firmware and found my battery full charge seems unaffected. There does appear to be some variance from day to day. Here are all of my full charge values which covers 11 full charge cycles according to the report:
2014-01-14 41,885 mWh 42,002 mWh
2014-01-15 40,993 mWh 42,002 mWh
2014-01-16 41,435 mWh 42,002 mWh
2014-01-17 41,445 mWh 42,002 mWh
2014-01-18 42,061 mWh 42,002 mWh
2014-01-19 40,197 mWh 42,002 mWh
2014-01-20 41,386 mWh 42,002 mWh
2014-01-21 42,193 mWh 42,002 mWh
2014-01-22 41,712 mWh 42,002 mWh
2014-01-23 41,215 mWh 42,002 mWh

 

[ihaveabu]

typically a battery should retain 80% of it's design capacity after a year or so. At this rate my SP2 will be at 80% in a matter of months...

 

[jrapdx]

FWIW I've been noticing similar fluctuating values in full charge capacity, which are hard to understand, how it's calculated isn't really clear.



It's also confusing how "cycles" are determined. The battery in my SP2 has been drained almost to zero (down to ~10%) well more than 4 times, but cycles reported is still only 4. Maybe that's right, but then what the heck is a "cycle"?

Oh well, not too much to do about it anyway--the battery is certainly not user replaceable. If the SP2 battery doesn't go the distance, we'll have to chalk it up to design failure. Time will tell.