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[Guide] Everything you wanted to know about Li-Ion batteries but were afraid to ask!

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By DarkDvr, Senior Member on 24th April 2010, 04:18 AM
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So after noticing how much of a difference people get in their battery lives, I've decided to do some research and make a guide-line that will give us all we need to know about properly using our batteries. First part is a general information and usage techniques for LIBs, second part is taken from Google materials on Android-powered devices (G1, Magic, Droid, Nexus One, etc).

Sources:

Wikipedia - http://en.wikipedia.org/wiki/Lithium-ion_battery
BatteryUniversity - http://www.batteryuniversity.com/parttwo-34.htm
Google IO Conference 2009 - http://www.youtube.com/watch?v=OUemfrKe65c
Electropaedia - http://www.mpoweruk.com/life.htm

General Lithium-Ion Battery (LIB) Usage:
  1. Discharging your LIB fully (or less than 2.4 Volt per cell) is bad for the battery. Every time you do that, it can be said that small part of your battery (some cells) dies (they forever lose their charge). Do not store your batteries depleted, there's a high chance they will die completely or will become very "weak".
  2. • You cannot restore bad LIBs by overloading/heating/praying. You gotta go buy a new one. They DO degrade overtime, some cells naturally lose the ability to gain/give electricity.
  3. • Although it is said that LIBs do not have memory, it's not entirely true. LIBs have gauges that monitor performance of cells, and if you do a lot of small charges, it won't let those gauges to monitor a full battery potential, causing an invalid indication of charge level. A complete charge/discharge should be made when battery capacity seems reduced, that will calibrate gauges and they will provide your phone with correct charge level status. A full charge/discharge cycle should be done every 30 (or so) partial charges.
  4. LIBs have a shelf-life. Do not buy them to store them. Use them early, use them often, they will die whether you use them or not. Do not buy LIBs to use them in 6 months/year/etc, buy them right before actually using them.
  5. LIBs have short lives (in comparison to NiCa batteries, etc). You should expect to buy a new battery in 2-3 years after being manufactured. It is caused by internal oxidation and there's nothing you can do to stop or prevent that.
  6. Worst LIB treatment is to keep it at 100% charge level at high temperature (think laptop/phone under direct sunlight, like car dashboard).
  7. Best LIB treatment, or LIBs "favorite" charge level - 40%. That's also the usual charge level you buy them with.
  8. LIBs don't like heat. For example, while always at 100%, typical LIB in a laptop, at temperatures of 25C (77F) will lose 20% (twenty percent!) of full capacity per year. That capacity loss is reduced to 6% (six percent) at 0C (32F), and increased to 35% loss at 40C (104F). So, keep them cool (LIBs like fridges), don't let your devices sit in the sun or overheat at charge. Also, keep in mind that while in use, battery will be significantly hotter than phone/outside environment

  9. • LIBs like frequent partial charges/discharges more than they like full charges/discharges.

General Android power usage advice from google:
  1. • Although this part is somewhat controversial, they do recommend having a complete, full FIRST charge to be made. If time allows, a preferred time for the first charge is 12 hours. This may have more to do with the OS than the battery.
  2. • Battery on a Android device, in average, will last about a full day with normal use (some videos, mail, calls). That's what you should kind-of expect.
  3. • Speaking in averages, "idling" 3G/EDGE connection (when phone is sleeping and no data is transferred through 3G), drains almost no energy. Just a little more than having 3G/EDGE radio off completely. So when no apps are using 3G, you don't need to keep it off.

  4. • Same goes to WiFi connection - although it's on, if there is no data flowing through it, it uses almost no energy.
  5. • At full throughput (100% data flow), EDGE is using more energy than 3G. In average, 3G is more energy-efficient than EDGE.
  6. • WiFi is using more energy than 3G (when both are at 100% use), but since it transfers files much faster and then goes to "sleep", it's actually recommended to use WiFi whenever possible. Since it'll "sleep" more often than 3G, overall it will use much less battery than using 3G.
  7. • Some bad apps or widgets can use android's "WakeLock", keeping CPU at 100%, screen always-on, or both. I myself have encountered such widget (I won't mention the name, it's in the market) that used a WakeLock to keep CPU spun-up at 100% all the time. That makes a huge impact on battery life. My advice - use a CPU profiling app to monitor the CPU - make sure that CPU slows down by itself when it's not used. So, beware of such widgets/apps. To check for CPU cycles, many recommend OSMonitor (free from market, install it, go to options, sort by "Load" in descending order. It'll give you "busiest" processes at the top). At rest you should be getting about 10-20% for OSMonitor itself, and 1-10% Android System. At rest, everything else should be 0-1%.
  8. • Android slows down CPU when not in use by itself, as a built-in feature. Apps that throttle/change CPU frequency, are not necessarily needed.


All this info comes from those reputable resources I mentioned above, I didn't make any of it up.
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24th April 2010, 04:33 AM |#2  
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Great info, thanks!
24th April 2010, 05:04 AM |#3  
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I'm curious where you get the 10-15% discharge warning. The articles frequently mention that the cells can die if they go below 2.4V, but they also mention that the circuitry in the batteries prevents the batteries from getting anywhere near that threshold. When the battery meter on the phone says 10-15% it is very likely not indicating "within 10 to 15% of causing serious harm", but actually indicating "within 10 to 15% of the lowest safe level that I will allow you to reach".

When you hit "0%" on the phone's meter which you must do to properly calibrate the battery, you should still be safely above the danger point, as long as you recharge the battery soon and do not let it sit for a few days or weeks. It is only when you get to 0% on the meter and then let it sit where the self-discharge can then cause it to approach the true danger levels.

Or, at least that is the way I have been reading the Battery University article for the past couple of years that I have been helping people with their Lithium Ion batteries, so please point out the text that might show a misunderstanding here as I don't want to be giving bad advice.

I typically tell people not to do regular deep discharges anyway as recharging from such a state causes more heat than a shallower recharge and the heat is one of the biggest enemies of these batteries.
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24th April 2010, 05:07 AM |#4  
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Another source for Lithium Ion recharging tips from the Battery University:

http://www.batteryuniversity.com/partone-12.htm

That page focuses more on charging concerns and provides some additional recommendations...
24th April 2010, 05:12 AM |#5  
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Thanks for pointing that out, that part its a general advice of when users should plugin their phones, coming from the information of trying to stick to a half-charge (or 40%) as close as possible. Besides, google decided to warn you at a 15% level, so this seems to be a good number to use.
24th April 2010, 05:19 AM |#6  
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Quote:

Another source for Lithium Ion recharging tips from the Battery University:



http://www.batteryuniversity.com/partone-12.htm



That page focuses more on charging concerns and provides some additional recommendations...

Thanks, indeed a great article. I decided not to include it in resources though, since it's a bit too technical for the purpose of this article.
26th April 2010, 06:22 AM |#7  
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Quote:
Originally Posted by DarkDvr

Thanks for pointing that out, that part its a general advice of when users should plugin their phones, coming from the information of trying to stick to a half-charge (or 40%) as close as possible. Besides, google decided to warn you at a 15% level, so this seems to be a good number to use.

The 40% charge is the charge level that you should "store" a battery at, not what you should keep it at when it is in use. Where do you see the 40% mark cited for any other purpose?

The 15% warning from Android is simply a warning that it is close to running out of power and may shut off if you don't go looking for a charger now. It is a practical warning to avoid the surprise of reaching 0% and shutting off when the user is not paying attention to the meter.

On the contrary, your first bullet item uses the word "BAD" in capital letters and spells doom and gloom about killing part of their battery if they go below that level. That amount of severity in that comment is completely unwarranted. It is not true and it will scare people off of using their batteries to their fullest capabilities and scare them off of doing calibration cycles when they need to do them. When the warning pops up you don't have to turn off your phone to avoid damage - just be aware that you only have 15% capacity left. And discharging to 15% and then recharging because you are scared by the advice in this thread from going lower will not recalibrate the battery meter.

Any way I look at it, your bullet item #1 is providing no value at all and could potentially scare people into non-optimal battery maintenance routines.
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26th April 2010, 06:25 AM |#8  
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Alright, I guess you got a point there.
I've corrected that bullet to be less tragic =)
26th April 2010, 06:28 AM |#9  
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Excellent rewording!
26th April 2010, 06:30 AM |#10  
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Quote:
Originally Posted by flarbear

Excellent rewording!

Thanks for your help
26th April 2010, 07:00 AM |#11  
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Great thread man! I knew most of that stuff already but didn't know about the WiFi's effect on the battery, I always thought it drained more battery than using 3G. I also didn't know it didn't drain any battery when not in use so thanks. Guess I'll be keeping that on from now on!
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