Useful Lithium Battery Information

carnageX

Private Joker,
Staff member
Messages
25,056
Location
Oregon
A couple of topics I've seen floating around XDA for a little while, and figured I would share them with everybody else, because I'm sure a lot of people have questions about their phone's batteries.

Note: I didn't write these, I have just quoted them/sourced them from their original posts/creators.

Xenova said:
Too many people I've met have misconceptions, wrong understanding or simply no idea at all about how to maintain the batteries inside their new spanking new electronic gadgets. More often than not, it will be one of those nifty, super-slim lithium-ion variants. So I decided to write this little primer to help you, erm, I mean, your techno-phobic friends along.

Note that my recommendations are catered along the lines of practical convenience as well as pure battery maintenance facts alone. As with everything, there is often more than a way to skin a cat. I do try to explain my rationale behind my recommendations, so do try to read on before clobbering me on the head with your PhD in advanced materials science.

Tip #1: Lithium-ion batteries are limited by their life-spans
Found an e-bay offer for a lithium-ion battery pack for your ageing notebook or PDA at bargain prices? Or saw that battery pack for your gadget in its dusty sealed package at the corner store of the flea market? Before you jump and snap it up, be sure to first check the manufacturer date.
We all know that all batteries are limited by a finite number of charging “cycles”. However, it is a little publicized fact that the lifespan of lithium-ion batteries are also limited by their manufacture date.

Your lithium-ion battery starts dying the moment it leaves the factory

The fact is, your lithium-ion battery starts dying the moment it leaves the factory! Of course, the actual life-span of an unused lithium-ion battery can vary by a fair amount based on its internal charge as well as the external temperature. But suffice to say that you can expect to irreversibly lose 20% of a lithium-ion battery's charge every year from its original date of manufacture.
PDA came with more than one spare battery? Take it out of its shrink-wrap and use it interchangeably – today. Thinking of buying a “spare” battery for use in future? Well, just save the money and buy it only when you are ready to use it.

Tip #2: Avoid allowing your device to discharge completely

Every wondered why your modern phone, PDA or iPod is able to cheerfully tell you that “Your battery is now exhausted” for several seconds on its brightly-lid LCD screen before switching off? The reason is simple; there is an artificial circuit that shuts off the device when the charge in the battery is too low.
This extraneous circuit is built to protect from the damage that could result if the charge of your lithium ion battery falls too low. If you still don't get it: if the charge of your lithium ion battery falls too low, the battery can get irreversibly and permanently damaged. So since Lithium Ion has no “memory effect”, it is better to simply charge your portable device as and when you can or remember.
To set your mind at ease, a “charge cycle” means a single iteration of depleting followed by a re-charge until 100% of battery charge. If you consume 50% of your iPod's battery on day 1, recharge to 100% at night, and do the same thing on day 2, then you would have just finished up one charge cycle of its battery life.

Constantly recharging a lithium ion battery does not shorten the battery life more than normal usage would

Hence constantly recharging a lithium ion battery does not shorten the battery life more than normal usage would. Avoid letting it sit on empty for too long; instead, keep it charged-up if you can.

Tip #3: Take the battery out of your notebook computer when connected to AC helps… not!

Well ok, actually, taking out the battery from your notebook computer might help, but the reason it does is not really what you think it is.
It is not because of over-charging as most people might believe. There are some really smart circuits monitoring your lithium ion battery (See reason #2 above), and these circuits also ensure that your precious lithium ion never gets overcharged. So leaving the battery in when the AC is on has no detrimental effect whatever on the health of the battery.

However, if there is another killer of lithium ion batteries other than old-age, then it would be heat. Long term exposure of a lithium ion battery to temperatures higher than 40 degrees Celsius permanently reduces its total charge capacity by noticeable percentages chunks per year. Having said that, I would hazard that modern processor like the Centrino Duo runs quite coolly overall.

On the other hand, it is really painful to see someone plug their AC adapter to their laptop, carefully remove the battery and put it aside, then finally sit down and switch on their laptop. Then have someone trip over their AC adapter an hour into an unsaved document. Ouch.

Unless you are setting up the laptop at Wal-Mart or Carrefour to run practically 24/7 until its time to sell it off at “display unit” pricing, my recommendation would be to save yourself the trouble and just leave the battery in. Actually, I think the real motivation to take the battery out of shop display units is to prevent theft. Really, why make it so inconvenient for yourself when the battery will be literally unusable in a few years time.


Source: 3 Things You Should Already Know About Your Lithium Ion Battery

-----------------------------------------------------------------------------
NEW ADDON:
Some also claimed that we should minimize the duration of the battery remain at high voltage (e.g. 4.2v / 100%). This is spoil the battery because the corrosion activities are relatively high when the battery is in high voltage/ full charge.
Put it short, after fully charge your battery, please use it ASAP. It won't give birth little baby battery if you leave it there with full charge :)
Source: Things You Should Know About Lithium Ion Battery - xda-developers
 
byrong said:
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.
Source: Your battery gauge is lying to you (and it's not such a bad thing) - xda-developers
 
Back
Top Bottom