Monday, 7 November 2011

Living & Technology: Lithium Battery Care, Your Phones and Cameras


(Updated 2011-11-09)
Battery Drain Problem of iPhone 4S
Ever since I started using Galaxy SII, I realise that the issue of battery drain is really quite serious, (but iPhone 4S also has this problem). So I have been trying all sorts of methods to reduce battery loss, there are some apps I am using and I do think they are quite good but I will leave it to the next blog entry to introduce them. Today, I want to talk about some research I did about the most important component of power in a smartphone, the battery -- Lithium-ion (Li) battery.

Ni-Cd Batteries
Image from itp.nyu.edu
There are many myths about rechargeable batteries, and we are going to crack them! But before we start, we have to learn 2 terms, "charge" is to add power to the battery, and "discharge" is to use the power from the battery.

Lithium-ion polymer battery
Image from Wikipedia
Lithium-ion battery is different from the traditional nickel metal hydride (NiMH) or nickel cadmium battery (NiCd) battery in many ways. The differences are listed below:

  1. Li-ion battery has a slow loss of charge (about 5-10% per month) , allowing the power to be stored in the battery for a longer time when not used. [1] This explains why the lithium batteries available in shops and supermarkets are usually charged to a certain amount. Cell phone batteries, known as Lithium-ion polymer batteries, are similar to the above, carries about 50% of a full charge for long period storage [3]. 
  2. Li battery has no "memory effect" which NiCd battery has. In simple words, NiCd batteries require overcharging in the first charge, then should be charged fully or even overcharged in the subsequent charges. [2] On the other hand, Li battery does not and MUST NOT be overcharged. [1]
  3. Li-ion polymer battery should not be fully-discharged (reaching 0% and idling the battery for a long period of time),  or else it may be damaged and may lose certain amount of capacity[3].

Image from sony.com.au
Summarising the points above, I have come to understand why my old Sony VAIO's laptop comes with a Battery Care Function which used to fix my Li-ion battery at 80% charge. In my entry Technology & Opinions: Hate. Believe. SONY, I talked about how much I hated this because Sony said this Function gives longer battery life, and I thought Sony was just bluffing! And so in the entry Message: SONY VAIO Battery Care, "I OWN YOU!!!" I mentioned that I have finally removed that Function and I finally get to charge my laptop 20% more, but looks like Sony was right all along! Full charging your Li-ion battery does shorten its lifespan.

So, after going through the researches , I have come to a simple conclusion of dealing with Li-ion batteries,

No 0%, No 100%, No memory.

It means that we should not leave battery at 0%, we should not full charge the battery, but we can charge as many times as we like.

Sounds great isn't it? But you might have to watch your battery charge from now on because your phone will  full charge itself without stopping, what can we do?

I have a solution for you in the next entry, if you are using Android smartphones.

(Updated 2011-11-09)
Apple has a nice and clear article on how Lithium battery works, and the key information have been extracted below for your better learning.



Lithium-ion Batteries
Rechargeable lithium-based technology currently provides the best performance for your Apple notebook computer, iPod, iPhone, or iPad. You can also find this standard battery technology in many other devices. Apple batteries share the characteristics common to lithium-based technology in other devices. Like other rechargeable batteries, these batteries may eventually require replacement.

Standard Technology

Lithium-ion polymer batteries pack in a higher power density than nickel-based batteries. This gives you a longer battery life in a lighter package, as lithium is the lightest metal. You can also recharge a lithium-ion polymer battery whenever convenient, without the full charge or discharge cycle necessary to keep nickel-based batteries at peak performance. (Over time, crystals build up in nickel-based batteries and prevent you from charging them completely, necessitating an inconvenient full discharge.)
Chart illustrating lithium-polymer battery voltage/cell and charge current over time during the fast and trickle charge stages


Standard Charging

Most lithium-ion polymer batteries use a fast charge to charge your device to 80% battery capacity, then switch to trickle charging. That’s about two hours of charge time to power an iPod to 80% capacity, then another two hours to fully charge it, if you are not using the iPod while charging. You can charge all lithium-ion batteries a large but finite number of times, as defined by charge cycle.
Charge Cycle. Using and recharging 100% of battery capacity equals one full charge cycle.
A charge cycle means using all of the battery’s power, but that doesn’t necessarily mean a single charge. For instance, you could listen to your iPod for a few hours one day, using half its power, and then recharge it fully. If you did the same thing the next day, it would count as one charge cycle, not two, so you may take several days to complete a cycle. Each time you complete a charge cycle, it diminishes battery capacity slightly, but you can put notebook, iPod, and iPhone batteries through many charge cycles before they will only hold 80% of original battery capacity. As with other rechargeable batteries, you may eventually need to replace your battery.



Vocabulary:
bluff -- (vb) [I or T] to deceive someone by making them think either that you are going to do something when you really have no intention of doing it, or that you have knowledge that you do not really have, or that you are someone else

Resources:
Lithium-ion battery @ Wikipedia
[1] http://en.wikipedia.org/wiki/Lithium-ion_battery


Memory Effect @ Wikipedia
[2] http://en.wikipedia.org/wiki/Memory_effect

Lithium-ion polymer battery @ Wikipedia

[3] http://en.wikipedia.org/wiki/Lithium-ion_polymer_battery


http://www.tekcomm.com.hk/
http://liionbms.com/pdf/ElithionBatteryPower10.pdf

News & Technology: iPhone 4S Battery Problem? @ Locky's English Playground
http://lockyep.blogspot.com/2011/10/news-technology-iphone-4s-battery.html

Technology & Opinions: Hate. Believe. SONY @ Locky's English Playground
http://lockyep.blogspot.com/2011/10/technology-opinions-hate-believe-sony.html

Message: SONY VAIO Battery Care, "I OWN YOU!!!" @ Locky's English Playground
http://lockyep.blogspot.com/2011/10/message-sony-vaio-battery-care-i-owned.html

Apple -- Lithium ion Batteries
http://www.apple.com/batteries/

http://dictionary.cambridge.org/dictionary/british/bluff_1?q=bluff