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Circumspice
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Topic # 228769 22-Jan-2018 00:43
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Just got a new XPS 13 and CPUID HWMonitor reports that it has a 4% wear level (full charge capacity is 57813 mWh, instead of designed capacity of 59994 mWh i.e. 60Wh). Have had it a fortnight now, HWMonitor reported this on day 2 when I installed it. Haven't completely discharged the battery. Is this report of 4% wear due to:

 

A) HWMonitor error

 

B) slightly worn battery

 

C) something else?

 

 

 

If B), is this to be expected? Thanks in advance.


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  Reply # 1944577 22-Jan-2018 05:14
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you need to look at where CPUID HWMonitor is getting its information from.

 

have you tried running the windows powercfg, battery report and energy?

 

Run as admin
Run from c:\
powercfg /batteryreport /output battery_report.html

 

powercfg -energy

 

then go into c drive and open the 2 reports

 

does you device have a battery calibration tool? maybe run that too


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  Reply # 1944589 22-Jan-2018 07:52
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Probably best not to get too concerned unless you are getting significantly less battery life than expected. There always seems to be some variance in capacity of these things and ambient temparture can also have an impact.

 

That said, if you haven't already, I suggest you let it calibrate/settle:

 

     

  1. Run it absolutey flat until the laptop shuts down.
  2. Leave it off and unplugged for a couple of hours
  3. Charge it up to max and then take another reading
  4. Also be worth checking you have the latest BIOS/Fimware for your laptop.




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  Reply # 1944590 22-Jan-2018 08:03
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I think you should ask Dell what their policies on batteries are, but some batteries are like that.

Never run the battery flat. They like to be between 20-80% capacity where they're happy. I set the bios to charge to 99% but don't charge until it drops below 80%. I set it to warn me at 25%.

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  Reply # 1944592 22-Jan-2018 08:29
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Batman:

Never run the battery flat. They like to be between 20-80% capacity where they're happy. I set the bios to charge to 99% but don't charge until it drops below 80%. I set it to warn me at 25%.

 

 

 

Would challenge "never" in the context of my post above. Running it to flat as described to re-calibrate the measurement and capacity reporting is not going to have a negative impact.

 

Completely agree that as a general operating rule, keeping it in the sweet spot you mention will help maximise battery life and minimize rate of degradation.

 

 

 

Edited to add:

 

Surprised you need to mess around in the BIOS with the charging level? My understanding is that my Macbook manages this "optimal" charging behind the scenes as standard by letting the battery rest/discharge slightly even when on power - I had assumed Windows laptops would do the same by default!

 

 

 

 





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  Reply # 1944594 22-Jan-2018 08:48
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Yeah I know, but I wouldn't do it.

 

You know the oxygen measurement probes you get in hospitals - how to calibrate them? Get some prisoners and make their oxygen levels go to 0 and see if the probes are well calibrated? I wouldn't do that.

 

But each to their own.


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  Reply # 1944597 22-Jan-2018 08:55
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Batman:

 

You know the oxygen measurement probes you get in hospitals - how to calibrate them? Get some prisoners and make their oxygen levels go to 0 and see if the probes are well calibrated? I wouldn't do that.

 

 

 

 

 

 

Hmm...

 

Laptop Battery Calibration ≠ Cold-blooded murder, but I think I get your point.

 

 

 

For OP, I stand by my post but would certainly add the caveat that you should try to avoid killing anyone whilst you conduct your calibration.





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  Reply # 1944672 22-Jan-2018 11:11
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Batman:

Never run the battery flat..

 

you wont be able to run the batt flat. Batt monitoring hardware will not allow it .

~flat~ as seen by the user wont be flat at all. Just will be the min batt voltage allowed .
That last small % of bat capacity will never be available to user .

 

Anyway, 4% is nothing.
Whats the accuracy of the software you are using . You could be within the margin of error.


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  Reply # 1944681 22-Jan-2018 11:36
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From Battery University:

 

  • Li-ion is maintenance-free and the battery lasts longest when operating between 30 and 80 percent
  • Like a machine that wears down quicker under strenuous work, so also is a battery stressed by harsh discharges and rapid charges
  • The worst combination is high voltage and elevated temperature. Store Li-ion at approximately 50 percent SoC
  • Partial charge is better than a full charge
  • Deep discharge wears the battery down

My Huawei phone has decent battery management. It charges to 80% very quickly, to 90% more slowly, then very slowly to 100%. I think it's trying to avoid a full charge, and the heat that comes with charging.

 

If you can set a battery's upper charge limit 80% is best, 90% is good. Never run it fully down, 30% is the minimum you should aim for.

 

Of course if you can replace the battery easily do whatever you like and just replace it a bit sooner.





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  Reply # 1944690 22-Jan-2018 11:54
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Unfortunately we buy a sleek portable laptop for long battery life, so we do need to maximise battery use when out, so using 80-30% means half the portable usage time.

A bit of a compromise here and there :)



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  Reply # 1951618 4-Feb-2018 22:03
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Weird I was sure I posted a reply a week ago. Anyway thanks again everyone for advice. I ran powercfg and it corroborated HWMonitor findings.

 

So I ran it down to 1%, and the "wear level" disappeared and full charge capacity is stated as 59994 mWh. Further, there was some odd behaviour before where it would charge to 59994 mWh and then when being depleted, 'skip' from 59994 to 57813 mWh.

 

PS - @batman, don't know about your XPS 13, but Dell Power Manager came preinstalled on mine and allows changes to the charge settings without going into BIOS


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  Reply # 1951679 5-Feb-2018 07:06
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Wow very interesting

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  Reply # 1951865 5-Feb-2018 10:53
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As posted above, letting your battery get below 30% reduces its lifespan. Taking it down to 1% wasn't a great idea. I doubt doing it once will matter, but you should re-read the advice I posted above, and stop worrying about the numbers so long as the battery life is ok.





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  Reply # 1951886 5-Feb-2018 11:19
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It takes a few charge cycles for Lithium batteries to reach their full capacity. I have my laptop which is 3½ years old set in the BIOS to charge to 85% maximum as it spends most of its time on a dock anyway. It has a 65Wh battery that at 85% charge has an apparent 53Wh capacity. So by my calculations it has lost a bit over 4% or 2.5Wh of capacity so far.




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  Reply # 1952043 5-Feb-2018 15:10
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@timmmay I took a calculated risk with one-off running it down. I figured at worst might lose a few %. For now it seems I've gained a few % - battery no longer skips from 59994 to 57813 mWh and instead drops gradually from 59994 mWh.

 

Have had personal experience of repeatedly running down to 0% with an XPS 12. That was back when I disabled the auto-sleep/shutdown when battery down to X% because I found that behaviour annoying (would be finishing some work as realised battery running low and it'd shut down - duh!). However it also had a fault that meant it often didn't shut down when I did a soft shut down, which meant it only shut down when battery was down to 0%. Stupidly, I didn't realise this for a while (bigger duh!). Battery got worn down to 70% capacity, but has held steady in last couple of years and it's now mostly hooked to power.


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  Reply # 1952046 5-Feb-2018 15:19
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I suspect you calibrated your software battery monitor at the expense of a small about of battery life. Doubt it will matter.




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