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As an Android user with many devices I'm usually not very concerned about battery, but Nexus 6P with Snapdragon 810 is somewhat notorious for its short battery life, so it makes me start to actually observe and care about it.

Even before that, I have a plug-in type USB voltage/current meter like this one below, that also measures the mAh that passed through:

enter image description here

With this I measure the full capacity (i.e. from the moment the device automatically powers off to it shows 100% and the meter shows no current drawn) of the battery, and compare the value to designed value from time to time.

Lately my Nexus 6P just went over its 1-year mark, and I did this measurement, which shows that the capacity shrank a considerable 400mAh from when I just got it. Before that I also checked my Nexus 4 which when retired was on its 2.5th year, and it shrank a whopping 600mAh, 28.6% of the design value.

Nexus 6P comes with USB-PD fast charging rated at 5V/3A, and it's not unheard of that fast charging will "wear down the battery life more quickly", but I've never seen any concrete proof (e.g. side-by-side comparison) that came with the claim.

This question also talks about whether the battery should be charged/discharged from a certain percentage, as a technique to increase battery lifespan. I often keep the device plugged for long, and charge the device below 15%, so I'm quite curious about the technique. The concept explained there, however, is mainly discharging cycle, which is not what I care much about, since I replace batteries after the device retires. What matters to me is the decrease in capacity, which directly affects day-to-day use in terms of battery life.

So my question boils down to these:

  • Does battery discharge cycle have any relationship with battery capacity?
  • What factors could affect battery capacity wear-down?
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    This is the first question I have asked in ages. Thanks for inspiration from @beeshyams - feel free to correct it to Android.SE scope by minor edits and tag addition. – Andy Yan Jan 22 '17 at 14:33
  • +1 As far as fast charging is concerned, I don't think you will get a side by side comparison ever but the jury is open. Samsung had made it optional for use to choose fast or normal charging (S6??), Probably in response to these apprehensions. See this question for reasons as to why I beleive it is bad – beeshyams Jan 22 '17 at 15:57
  • @beeshyams That's quite unfortunate, but I understand as it's quite costly and time-consuming to do an experiment like that... – Andy Yan Jan 22 '17 at 23:46
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Does battery discharge cycle have any relationship with battery capacity?

Yes

The more you use the battery , more the number of discharge cycles ( which covers both charging and discharging as explained earlier) and drop in battery capacity as illustrated in this figure, which shows capacity drop as the number of cycles increase for Li Ion batteries of different capacities

enter image description here

Source

What factors could affect battery capacity wear-down?

  • Cycling or the amount of use in terms of charge cycles covered above

  • Elevated temperature :

    • Physically exposing the device to high temperatures ( like on a dashboard of car on a sunny day) or

    • Increase in internal temperature, by keeping a cell at a high charge voltage (hence the reference to ideal voltages, which doesn't permit build up of temperature )

Exposing the battery to high temperature and dwelling in a full state-of-charge for an extended time can be more stressful than cycling

  • Aging: This source at the end talks of the chemical reasons that cause aging. Without getting into the chemistry of it, what it means is that the capacity of battery starts decreasing from the day it is manufactured, represented by the active zone in figure

enter image description here

Additional Information

Edit Accubattery Pro gives you an indication of estimated Vs actual capacity as shown below. I have no idea how accurate it is but surely can be indicative

enter image description here

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    Yes, just what I want! I knew it takes that expertise from you to answer it :) Will accept if nothing exceptionally better pops up. – Andy Yan Jan 22 '17 at 23:45
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    Glad to help. Not expertise really, I just hate wasteful consumerism and batteries are a part of planned obsolescence shoved down our throats - you hardly see any replaceable batteries – beeshyams Jan 23 '17 at 3:41
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    Who doesn't? I cannot tell you the amount of friends I have that toss their old phones because the internal battery is failing and it's not economically worth it to them to replace the battery and instead replace the whole device. Also, that final graphic is probably the best explanation of battery aging I've ever seen. Of course, it's not exactly like that, but an excellent description. – Ethan Z Jan 24 '17 at 16:30
  • @EthanZ: Glad you liked it . Simplicity is preferred over chemistry ! – beeshyams Jan 24 '17 at 16:34

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