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Why don't handset manufacturers trust us to see the real battery level?


The battery meter on your phone is lying to you. Why don't handset manufacturers trust us to see the real battery level? This is something that has bugged me for ages and since it's also evident on the HTC One, I thought i'd post a little rant.

So what's the deal? Basically, the battery meter display on most devices doesn't correlate correctly with the actual battery left. Typically, they seem to initially indicate more is left than really is to begin with, becoming more representative as the battery is depleted. Why? I don't really know... maybe it's to give the impression that your battery is 'doing better' than it really is?

This is an analysis of the battery images on the HTC One. The 40% indicator is the only one (aside from full and empty of course) that is actually correct and no, it's not an error - the 80% and 90% images are exactly the same! I've pulled out the 10 images and correlated them with the maximum battery percentage for which they are displayed.

Posted Image


If you're on a nice big screen it might not be immediately evident how significant the 'errors' are, but on device, it's really quite clear.

I'm going to reach out to HTC to see if they can explain why this is the case... any thoughts? Battery meters with a 100 image split instead of 10 are definitely the way to go (i'm not a fan of textual percentage representation myself)...

About the author

PaulOBrien's Photo
Paul O'Brien founded MoDaCo in 2002 as a site focused on Windows Smartphones and has grown it since then by concentrating on providing a friendly community for both experienced and beginner mobile enthusiasts.

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7 Comments

What's the method of calculating the battery levels?
Is it just a table that relates battery voltage to retaining battery capacity?
Or does an android has a battery current sensor for measuring the real current that is drawn from the battery (multiplying/intergrating over time results in mAh that can easy be related to the known total battery capacity (mAh)?
Is there a way to "correct" the used method?
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BiggidyBoing
Mar 29 2013 08:59 PM
I suspect it's most likely for psychological reasons to help prolong the battery. Many people say it's best to keep lithium-ion batteries within the 40-80% range, so perhaps the icons are encouraging that. Making it appear more full until you get below 50% so as to discourage pessimistic users from needlessly overcharging it.

It's impossible to accurately know what the level truly is with Li-ion batteries. The device mostly guesses from the amount of time voltage+current has been fed into the battery versus the amount of time spent draining from it. Which is why it can be good to let it fully discharge once a month to recalibrate the counters.
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maniac_mouse
Mar 31 2013 03:20 AM
I always thought it was psycological as well. People like the battery level to be 100% when it comes off the charger, and most people leave the phone attached to the charger for longer than needed to reach full charge (overnight for example). When the phone is fully charged (true 100%) the charging circuit will disengage and let the battery charge drop a few percent (say to 95%) before kicking in again to bring it back to 100%. If you unplug it whilst the true charge is 96% for example, it still displays 100% because thats what you expect it to say after a night of charging and it gradually corrects itself until the proper value is displayed. It does it to prolong the battery life and to protect against overheating. Also, if it displays anything under 100% after hours of charging, people are going to think the phone, battery or charger are faulty.
On my galaxy note, it tends to drop the first 20% quite rapidly, then slowdown as it approaches 50%.
I dont think it matters that much to be honest as below 50% its pretty accurate. And being accurate near the end of its charge is more important to know than at the top end.

I have a circular battery indicator with about 50 segments in it and the % displayed in the middle, so it does reflect the charge level quite well. The bar one on this rom exibits the same behavior as the one paul tested so i guess the answer is to not use that type of indicator if you want accuracy.
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I've noticed the same exageration taking place with the radio signal level icon on newer versions of Android >froyo but you all probably haven't noticed because you are on Jelly bean already right..?
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Droid2drummer
Apr 14 2013 02:02 PM
This indeed has been noticed on many devices. I believe it android in general. My D2 ( moto droid) s3 RAZR and rezound up to the nexus4 current and each device in between I've noticed ..especially since this has been known for some time I've used both battery and numbers. Even then, still not completely accurate. At first with og droid days and eris I never really paid attention. But used to blame myself in thought of not doing battery stats wipes. Thus feeling a stat wipe wasn't doing anything in addition to the reset. Lol thanks for this post. I'm not alone. Lol peace
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