HWZ Forums

Login Register FAQ Mark Forums Read

Batteries, charging, and you: Why no 100% charge on your phone

Reply
 
LinkBack Thread Tools
Old 16-01-2011, 03:56 PM   #1
Moderator
 
Vulpix's Avatar
 
Join Date: Jan 2000
Posts: 92,692
Talking Batteries, charging, and you: Why no 100% charge on your phone

I realize that much of this is common knowledge on XDA. Still, every day I see people post about how their phone "loses" 10% as soon as it comes off the charger. I also have friends who can't understand why their battery drains so quickly. Trying to explain this to people without hard numbers is often met with doubt, so I figured that I'd actually plot it out with real data.

So it's not a piece that is optimized for this audience, but I hope that you find it interesting.


--------------------------------------------------

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.



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.



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?



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?



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.
Credits: byrong
Original thread: http://forum.xda-developers.com/showthread.php?t=871051

So before you post about your battery not charging to full and think it's a bug, it's not.
__________________
Path of Exile REVIVAL thread!

Last edited by Vulpix; 16-01-2011 at 04:00 PM..
Vulpix is offline   Reply With Quote
Old 16-01-2011, 04:18 PM   #2
Senior Member
 
PC-User's Avatar
 
Join Date: Dec 2007
Posts: 1,069
I've been long doing the top-up charge for any Li-Ion device myself but I still fail to convince my colleagues to do that which is a pity. I often see them reaching for the charger at work as their batteries are flat because they don't dare to charge at home while the batteries are not 'finished'.

Recently when I bought the Motorola Defy, the quick start sheet stated an initial charging time of 3 hrs which impressed me. Finally no more '8 hrs initial charge' tradition as with older generation phone. But still most retailers/shop keepers are still living under the old believing.
PC-User is offline   Reply With Quote
Old 16-01-2011, 05:02 PM   #3
Moderator
 
Vulpix's Avatar
 
Join Date: Jan 2000
Posts: 92,692
I've been long doing the top-up charge for any Li-Ion device myself but I still fail to convince my colleagues to do that which is a pity. I often see them reaching for the charger at work as their batteries are flat because they don't dare to charge at home while the batteries are not 'finished'.

Recently when I bought the Motorola Defy, the quick start sheet stated an initial charging time of 3 hrs which impressed me. Finally no more '8 hrs initial charge' tradition as with older generation phone. But still most retailers/shop keepers are still living under the old believing.
In the first place, there is no need for the "8 hours charge" for lithium batteries. The 8 hours thing was brought over from the old NiMH generation. Now that phone manufacturers are starting to realize that they need to make the batteries itself last long (as in life span, not how long your phone can remain switched on), we've come a long way in battery charging optimizations.
__________________
Path of Exile REVIVAL thread!
Vulpix is offline   Reply With Quote
Old 22-02-2011, 04:53 PM   #4
Senior Member
 
xcubepro's Avatar
 
Join Date: Jul 2000
Posts: 2,055
another article which i feel is a good read about Li-On batteries
http://arstechnica.com/gadgets/news/...on-battery.ars
__________________
[URL="http://www.biteandbytes.com"]www.biteandbytes.com[/URL]
My name is Christine. [B]Don't call me "BRO"[/B].. lolx
OnePlus One 64GB | iMac 27" (Late 2012) | iPad Mini Retina Display (32GB LTE) | Asus Nexus 7 2nd Gen (16GB) | Apple iPod Touch (5th Gen) | Samsung Galaxy Tab 7.7 | Apple MacBook Air 11" C2D/4GB RAM
xcubepro is offline   Reply With Quote
Old 06-03-2011, 03:10 PM   #5
Senior Member
 
eS.KuKu's Avatar
 
Join Date: Dec 2009
Posts: 1,224
another article which i feel is a good read about Li-On batteries
http://arstechnica.com/gadgets/news/...on-battery.ars
This is nice! good guidelines.
__________________
eSŪ
eS.KuKu is offline   Reply With Quote
Old 21-03-2011, 05:51 PM   #6
Master Member
 
Join Date: Sep 2000
Posts: 3,281
Just realised when I bought the Nexus S, the sales person finally didn't ask me to charge it for 8hrs.
RtOaNn is offline   Reply With Quote
Old 29-03-2011, 08:51 PM   #7
Member
 
Join Date: Sep 2009
Posts: 362
It's still very hard to convince retailers that phone nowadays don't require 8 hrs initial charge, as you know Singapore's handphone dealers are mainly made up of people who think they know it all.

And btw, a very good and detailed explanation.
CallMeChun is offline   Reply With Quote
Old 26-04-2011, 04:49 PM   #8
Senior Member
 
takakotokiwa77's Avatar
 
Join Date: Jan 2005
Posts: 725
Li-Ion vs NiCad facts had been proven no longer myth...

now i guess is the USB vs Wall charging topic...
1 thing i notice is wall charge often heats up the battery which is bad...
other than that wall charging is faster compared to USB but some say the wall charging battery discharge slower than USB when daily use... Myth?

Thanks in advance
__________________
Marantz CD6004 -> Woo Audio WA2 -> Beyerdynamic))) T1 Tesla
takakotokiwa77 is offline   Reply With Quote
Old 25-05-2011, 05:57 AM   #9
Senior Member
 
Hitsugaya87's Avatar
 
Join Date: Jan 2007
Posts: 1,433
Never met any difference in battery power charging through USB/AC, but its true that USB takes longer to charge than AC. Other than that, don't see or feel any major differences.
__________________
When done with love, even the most simplest of things can turn out to be the most beautiful.

DAP: iBasso DX100, Cowon J3, Sansa Clip Zip
Amps: Pico Slim, RSA Mustang P51
Earphones: UM3x, UE SF5 pro, ER4p, ER4s (custom)
Headphones: Sony Z1000, Grado SR325i
Hitsugaya87 is offline   Reply With Quote
Old 25-05-2011, 07:42 AM   #10
Supremacy Member
 
oddbasket's Avatar
 
Join Date: Sep 2003
Posts: 7,001
Li-Ion vs NiCad facts had been proven no longer myth...

now i guess is the USB vs Wall charging topic...
1 thing i notice is wall charge often heats up the battery which is bad...
other than that wall charging is faster compared to USB but some say the wall charging battery discharge slower than USB when daily use... Myth?

Thanks in advance
Myth......
oddbasket is offline   Reply With Quote
Old 24-08-2011, 05:38 AM   #11
Junior Member
 
Join Date: May 2010
Posts: 95
I hv both iDevice and Android phone ( Dezire Z ,rooted) and I do notice that USB charging is slow compare to power adapter in my desire Z, but how come iP4 charging speed are the same in both situation and why android can't do that ?

any idea?
__________________
My devices: htc magic, htc desire Z, iPhone4, iPad2
www.askabouthugo.com
hugophang is offline   Reply With Quote
Old 07-09-2011, 03:17 PM   #12
Junior Member
 
Join Date: Sep 2011
Posts: 3
Thumbs up bravo

you guys are genius
komexman is offline   Reply With Quote
Old 19-11-2011, 05:27 AM   #13
High Supremacy Member
 
kennyboy's Avatar
 
Join Date: Nov 2000
Posts: 42,496
This article is also rather informative as to the differences between USB and AC charging. Iphone based, but the info inside works across the board generally.

http://arstechnica.com/apple/guides/...m_campaign=rss
kennyboy is offline   Reply With Quote
Old 30-11-2011, 01:14 AM   #14
Junior Member
 
Join Date: Nov 2011
Posts: 14
I could only solve battery and charging issue on my Nexus S when I bough myself a 3900mAh extended battery. I use Mugen Power.
derekdroid is offline   Reply With Quote
Old 22-02-2012, 09:39 PM   #15
Junior Member
 
Join Date: Feb 2012
Posts: 7
So it's true now we do not need do the mandatory 8 hour charge for new phones? I suggested it to my friend who sells smartphones and he scoffed at this idea
shogunism is offline   Reply With Quote
Reply
Important Forum Advisory Note
This forum is moderated by volunteer moderators who will react only to members' feedback on posts. Moderators are not employees or representatives of HWZ. Forum members and moderators are responsible for their own posts.

Please refer to our Terms of Service for more information.


Thread Tools

Posting Rules

Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are On