14
Dec
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This article was written by a guest poster Byron G and originally posted to his blog. It is reprinted here with Byron's full permission.

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Your Smartphone Is Lying To You (And It’s Not Such A Bad Thing)

Climbing out of bed, about to start your day, you unplug your new smartphone from its wall charger and quickly check your email. You’ve left it plugged in overnight, and the battery gauge shows 100%. After a quick shower, you remember that you forgot to send your client a file last night. You pick up your phone again, but the battery gauge now reads 90%. A 10% drop in 10 minutes? The phone must be defective, right?

A common complaint about today’s smartphones is their short battery life compared to older cell phones. Years ago, if you accidentally left your charger at home, your phone could still make it through a weeklong vacation with life to spare (I did it more than once). With the newest phones on the market, you might be lucky enough to make it through a weekend.

And why should we expect anything else? Phones used to have a very short list of features: make and receive phone calls. Today we use them for email, web surfing, GPS navigation, photos, video, games, and a host of other tasks. They used to sport tiny displays, while we now have giant touch screens with bright and vibrant colors. All of these features come at a cost: large energy requirements.

Interestingly enough, improvements in battery management technology have compounded the average user’s perception of this problem. Older phones were rather inelegant in their charging behavior; usually filling the battery to capacity and then switching to a trickle current to maintain the highest charge possible. This offered the highest usage time in the short-term, but was damaging the battery over the course of ownership. As explained at Battery University, “The time at which the battery stays at [maximum charge] should be as short as possible. Prolonged high voltage promotes corrosion, especially at elevated temperatures.”[1]

This is why many new phones will “lose” up to 10% within a few minutes of coming off the charger. The reality is that the battery was only at 100% capacity for a brief moment, after which the battery management system allowed it to slowly dip down to around 90%. Leaving the phone plugged in overnight does not make a difference: the phone only uses the wall current to maintain a partial charge state.

To monitor this, I installed CurrentWidget on my HTC ADR6300 (Droid Incredible), an app that can log how much electric current is being drawn from the battery or received from the charger. Setting it to record log entries every 10 seconds, I have collected a few days worth of data. While many variables are involved (phone hardware, ROM, kernel, etc) and no two devices will perform exactly the same, the trends that I will describe are becoming more common in new phones. This is not just isolated to a single platform or a single manufacturer.

Chart 1 shows system reported battery levels over the course of one night, with the phone plugged in to a charger. Notice that as the battery level approaches 100%, the charging current gradually decreases. After a full charge is reached, wall current is cut completely, with the phone switching back to the battery for all of its power. It isn’t until about two hours later that you can see the phone starts receiving wall current again, and even then it is only in brief bursts.

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Chart 1 - click to enlarge

The steep drop in reported battery seen past the 6.5 hour mark shows the phone being unplugged. While the current draw does increase at this point (since the phone is being used), it still cannot account for the reported 6% depletion in 3 minutes. It should also be obvious that maintaining a 100% charge state is impossible given the long spans in which the phone is only operating on battery power.

Using the data from CurrentWidget, however, it is quite easy to project the actual battery state. Starting with the assumption that the first battery percentage reading is accurate, each subsequent point is calculated based on mA draw and time. Chart 2 includes this projection.

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Chart 2 - click to enlarge

Now we can see that the 6% drop after unplugging is simply the battery gauge catching up with reality.
The phone manufacturers essentially have three choices:

1. Use older charging styles which actually maintain a full battery, thereby decreasing its eventual life

2. Use new charging methods and have an accurate battery gauge

3. Use new charging methods and have the inaccurate battery gauge

Option one has clearly fallen out of favor as it prematurely wears devices. Option two, while being honest, would most likely be met with many complaints. After all, how many people want to see their phone draining down to 90% while it is still plugged in? Option three therefore offers an odd compromise. Maybe phone companies think that users will be less likely to worry about a quick drop off the charger than they will worry about a "defective" charger that doesn't keep their phone at 100% while plugged in.

Bump It. Or Should You?

One technique that has gained popularity in the user community is "bump charging." To bump charge a device, turn it off completely, and plug it into a charger. Wait until the indicator light shows a full charge (on the ADR6300, for example, the charging LED changes from amber to green) but do not yet turn the device back on. Instead, disconnect and immediately reconnect the power cord. The device will now accept more charge before saying it is full. This disconnect/reconnect process can be repeated multiple times, each time squeezing just a little bit more into the battery. Does it work?

The following chart plots battery depletion after the device has received a hefty bump charge (6 cycles) and then turned on to use battery power. Note that the system does not show the battery dropping from 100% until well over an hour of unplugged use, at which point it starts to steadily decline. Again, however, it should be obvious that the battery gauge is not syncing up with reality. How could the rate of depletion be increasing over the first 5 hours while the rate of current draw is relatively steady? And why does the projected battery line separate from the reported levels, but then exactly mirror the later rises and falls?

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Chart 3 - click to enlarge

The answer, of course, is that bump charging definitely works. Rather than anchoring our projected values to the first data point of 100%, what happens if we anchor against a later point in the plot?

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Chart 4 - click to enlarge

Aligning the data suggests that a heavy bump charge increases initial capacity by approximately 15%. Note that the only other time that the lines separate in this graph was once again when the phone was put on the charger and topped up to 100%. Just as with the first set of graphs, the phone kept reporting 100% until it was unplugged, dropped rapidly, and again caught up with our projections.

So What Does It All Mean?

If you absolutely need the highest capacity on a device like this, you will need to bump charge. There are currently people experimenting with "fixes" for this, but I have yet to see one that works. Be warned, however, that repeated bump charging will wear your battery faster and begin to reduce its capacity. If you are a "power user" who will buy a new battery a few months from now anyway, this presumably isn't a concern. If you are an average consumer who uses a device for a few years, I would recommend that you stay away from bump charging. The bottom line is that you don't really "need" to do it unless you are actually depleting your battery to 0% on a regular basis.

If you are someone who can top off your phone on a regular basis, do it. Plug it in when you're at home. Plug it in when you're at your desk. As explained by Battery University, "Several partial discharges with frequent recharges are better for lithium-ion than one deep one. Recharging a partially charged lithium-ion does not cause harm because there is no memory."[2]

Beyond that, the best advice I can offer is to stop paying such close attention to your battery gauge and to just use your phone. Charge it whenever you can, and then stop obsessing over the exact numbers. If you really need more usage time, buy an extended-capacity battery and use it normally.

Artem Russakovskii
Artem is a die-hard Android fan, passionate tech blogger, obsessive-compulsive editor, bug hunting programmer, and the founder of Android Police.
Most of the time, you will find Artem either hacking away at code or thinking of the next 15 blog posts.

  • http://me@GrantGarrison.com OMGrant

    You should have titled this "Assault on Battery"

    :)

    • Abhi

      One of the best article i read

  • tmwsiy

    thanks very much for the informative and interesting article, it explains a lot and answered a couple of nagging questions I always had with my battery.

  • Bek

    Great article! Thanks for putting it together!

  • MushroomStamp

    Finally a good article explaining battery life.

  • CodeMonkey

    Good article, and reassuring to know that I've unwittingly been taking the right approach by using a desktop dock at work and one at home

  • http://facebook.com/ketchupmakesmeCRINGE Chris

    Would read again

  • http://www.rowald.net Rob

    I Laughed; I Cried; It was better than Cats.
    I'd read it again and again...

  • Charlotte

    I'd like to thank you for this post. It was very informative. and to people who contantly complain about battery life - get an extra battery. then you don't have to think about this stuff.

  • http://alexdemo.site90.com abeee

    I would like to propose option 4:

    scale the original 0% to 90% to indicate 0% to 100%. This could cause the display to show > 100% battery charge. In that case make the software show a maximum of 100%.

  • http://www.cypher_sec.org thecolor

    I'm curious how this might apply to my Individual battery charger. I swap batteries as they die always having a spare that had been on a battery charger. Would that not also be similar or does it too need to be fully charged, unplugged and bumped?

  • http://dangerismymiddlename.coms Paul Danger Kile

    I seem to get more life by letting it drain to 0 and then charge to 100. This has me wondering if my perception is way off. Thank you.

  • portnoyd

    Nicely done. I <3 bump charging. My DX has very, very nice battery life because of it.

  • http://www.vasanth.in Vasanth Dharmaraj

    Nice and informative article. Now I am not too worried about the drops in battery gauge.

  • Peter

    Interesting stuff.

    My battery goes to 90% after a few minutes and turns off between 15% and 13%. If nothing else the phone makes need to present the data better. The perception given is that I'm only getting 75% of a charge.

  • spyder

    That explains what my Evo was doing... unplug it and watch it drop to 90% in a few minutes, then 80% in a few more, then stabilize for awhile. But it doesn't describe my MyTouch 4G which stays at 100% for about half a day than starts the 45 degree downward drop on BatterGraph.

  • http://twitter.com/dennisdyallo Dyallo

    Thanks, appreciate it!
    Will try it asap!

  • Keemotherapy

    omg I just had to say thank you for the information! Very inciteful! Especially about the battery bump! Thank you!!!

  • Mark

    Very nice and informative article. Loved it.

  • boogi

    And I thought it was to remind us that nobody is perfect :-)

  • RB94928

    I have an HTC EVO I have found that if I don't use live wallpapers like Maps I can get 12 hours easy heavy use and 24 hrs lite use. 1d5h24m since unplugged. With maps live wallpaper running This would be cut in half. It would be nice if this could be corrected. As for now I have 2 extra batteries a car charger and a wall charger for the extra batteries. This keeps me going with out a hitch on heavy use days.

  • http://www.albertoischia.it/blog/ Giovanni

    Thanks. A clear explanation of how to use the best battery. Excellent article. Excuse my English

  • Loops

    Very informative. Any input on Advance Task Killer app as a battery drain? The Verizon reps automatically put it on my phone without asking.

  • Drakman

    Maybe I missed the part describing the planned obsolescence and how these are designed to fail so you'll buy more and more crap you never needed in the first place (face it - you are not that important/popular) and only want now because the inferior product that you over-paid for is falling apart/failing exactly as it was designed to do.

    Sheep.

    • Mike Mckelvy

      There is no such thing as planned obsolescence. Think like a person who wants return business. Think about the competition using that sort of information against you in their ads. Well their phone's battery dies after 6 months but ours lasts 2 years.

      • MrTJ

        Mike,

        How naive you are. There is no "free market", only see what other are doing. . All business is conducted by perceived market value and/or gullibility of consumer, never ever on inherent/true value plus a justifiable profit. It's get them hooked, then exploit and then drain drain drain (Steve Jobs motto). As long as we let business exploit human weakness we get 6 month batteries, never 2 years unless they are required to buy an external force (Consumers are a very very very week force). In developed counties, people purchase based on vanity, envy and peer pressure 99% of the time (worst offenders: diamonds and cell phones). Until these truths are taught and understood by all individuals, consumers do not stand a chance against businesses marketing in the billions. In this day and age of consumer analytics, purchase tracking we should be arming all new consumers in grade, middle and High schools tools to combat and recognise their own human weakness and defuse the hype they are exposed. The 3 R’s should be expanded to 4 R’s ; Reading wRiting, aRithmatic and woRth.

        Now I pose to you, Think like a dirty %^&^&%^&@##@ greedy bastards that currently run most high demand product/service businesses. Do you design a product that has a 6 month life cycle or 2 years? Not one business will design for 2 years, in the name of share holder value. They will look out the window see the competitors are designing for 6 and they will too. Look at Ford; they knew they designed poorly the Pinto and Bronco. They calculated that it was cheaper to litigate and pay off surviving families then to fix the defects. Nice one, no one went to jail. Banks recently lost millions needing to be bailed out, did anyone go to jail?

        There are no current safeguards in place to prevent exploitation of human weakness of baubles. Big business also coins phrases like “disposable income” to obscure the pilfering of non essential spending.

        Consumers need to put pressure on governing bodies to assist in the education and protection of greedy ogre like businesses.

  • Marius

    Verry interesting article... thanks. Now everything makes sense :D

  • http://www.connexxion9.com blast0id-_-b

    "Beyond that, the best advice I can offer is to stop paying such close attention to your battery gauge and to just use your phone."
    best quote of the whole article! stupid fools and their need for "battery percentage icons" in the taskbar... quit being so anal and just use your damn phones! this is why I purposely hide my taskbar... though I do use WP Clock which shows percentage... I don't pay attention... really only reason I use WP Clock is for date time on all home pages...

  • kay

    yepp, thanks. useful and appreciated info. due to power consumption of a Desire HD frequent charging whenever possible is a necessary routine to me. unfortunately higher capacity batteries won't fix this issue :) didn't realize before that intermediate charging is generous battery treatment at least..

  • Rohit

    Good analysis. Really helpful

  • Alessandro

    Thanks a lot for the explaination, i am going to reshare this on my G+ account ^_^

  • http://nexusfaq.wordpress.com mandiom

    Very informative and really well done! Thanks a lot, I've been mentioning your article all over forums etc ;)

  • Brad

    I have a Samsung Mesmerize and left it plugged in overnight and as soon as I unplugged it the battery wasn't even charged. It's only happened once but will try bumping it for sure.

  • Yan

    Best article I read!!!!! Thanks

  • http://www.facebook.com/profile.php?id=1404934964 Giovanni Guzman

    Interesting, I'll be sure to remember this when i get my Galaxy S3, My phone right now last 4 days with a good nights charge..That tip above should help me a ton, thanks :)

  • JFG

    I've just read this interesting article. But I haven't noticed this sudden drop from 100%. Don't you think that now the reported % has been rescaled so that reported 100% is really about 90% or so?

  • tye6tyhtyh

    sexy

  • Amit

    best article so far I have read

    • Kostas

      Keep reading... you have 3.5 years to catch up! It gets better :D

  • letty

    Sometimes my battery charges overnight and sometimes it doesnt. Should I wait until its depleted or can I charge it at 35%?

  • ReyDR

    I'm interested on how you compute for the "Calculated Battery Level" based on the result from CurrentWidget. Can you share this?

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