Submit Hint Search The Forums LinksStatsPollsHeadlinesRSS
14,000 hints and counting!

An overview of laptop battery technology System
Most laptops now use lithium ion (LiIon) batteries. LiIons should be managed differently from the NiCad or NiMH batteries used in older laptops. In particular, LiIons should not be run all the way down to prevent "memory effect". First, they don't have a memory effect, and second, running them down tends to reduce their capacity. If the laptop does not need the battery it should be run to about 40% charge and stored in a cool place. LiIon batteries go bad whether used or not, so only buy new LiIons. Typical life is 2-3 years.

Why are iBook and Powerbook batteries so expensive? Part of the reason is that LiIon batteries can do bad things if they overheat (creation of Lithum metal which "burns" in water, chance of fire). So LiIon battery packs have an internal circuit to prevent overcharging (which would cause them to overheat). There can be several functions for the protection circuit, including shutting it down in case of over charging, when the voltage drops to a predefined level, or if it thinks the battery is otherwise damaged.

Problems with the power circuit can cause a "good" battery to shut down. The recent post about fixing iPod batteries likely had to do with re-setting something in the battery protection circuit that caused it to shut the battery off early. Isidor Buchmann's Batteries in a Portable World site talks about methods some have used to try to reset the protection circuit on batteries that seem to have died young.

Trying to reset a LiIon protection circuit is dangerous to try yourself - you could end up with a nasty fire. Plus the electrolyte is flammable and caustic, so it needs to be well packaged to make a spill unlikely, even if you do manage to overheat it.

All this costs, which helps explain the price of the batteries...

[robg adds: I know this isn't exactly an OS X hint, but battery questions seem to come up a lot. The referenced website has to be one of the most throrough I've ever seen; the online book goes into more detail than I thought possible on the subject! The remainder of this hint has some snippets from the book, along with URLs to the pages the snippets were taken from. Read on if you'd like to get a feel for what's on the site, or just go visit Isidor's website and read the whole thing online.]

Summary of excerpts on using LiIons from Batteries in a Portable World:
  • There is no memory and no scheduled cycling is required to prolong the battery's life.
  • The typical life span of a Li-ion battery is two to three years, whether it is used or not.
  • The internal resistance of the Li-ion batteries cannot be improved with cycling. The cell oxidation, which causes high resistance, is non-reversible. The electrolyte slowly eats up the positive plate and the electrolyte decays. This chemical change causes the internal resistance to increase. In time, the cell resistance raises to a point where the battery can no longer deliver the energy.
  • The recommended storage temperature of a lithium-based battery is 15°C (59°F) or less. A charge level of 40 percent allows for some self-discharge that naturally occurs; and 15°C is a practical and economical storage temperature that can be achieved without expensive climate control systems.
Simple Guidelines:
  • Charge the Li-ion often, except before a long storage.
  • Store at about 40% charge in a cool place
  • Avoid repeated deep discharges.
  • Keep the Li-ion battery cool.
  • Prevent storage in a hot car.
  • Never freeze a battery.
  • If your laptop is capable of running without a battery and fixed power is used most of the time, remove the battery and store it in a cool place.
  • Avoid purchasing spare Li-ion batteries for later use.
  • Observe manufacturing date when purchasing.
  • Do not buy old stock, even if sold at clearance prices.
Here are some particularly interesting pages from the book (which can be read online after completing a simple registration form):
  • Chapter 2 Page 6:
    The Li-ion is a low maintenance battery, an advantage that most other chemistries cannot claim. There is no memory and no scheduled cycling is required to prolong the battery's life. In addition, the self-discharge is less than half compared to NiCd and NiMH, making the Li-ion well suited for modern fuel gauge applications.
  • Chapter 6 Page 3:
    Li-ion offers internal resistance characteristics that are between those of NiMH and NiCd. Usage does not contribute much to the increase in resistance, but aging does. The typical life span of a Li-ion battery is two to three years, whether it is used or not. Cool storage and keeping the battery in a partially charged state when not in use retard the aging process.

    The internal resistance of the Li-ion batteries cannot be improved with cycling. The cell oxidation, which causes high resistance, is non-reversible. The ultimate cause of failure is high internal resistance. Energy may still be present in the battery, but it can no longer be delivered due to poor conductivity.
  • Chapter 6 Page 1:
    The loss of charge acceptance of the Li-ion/polymer batteries is due to cell oxidation, which occurs naturally during use and as part of aging. Li-ion batteries cannot be restored with cycling or any other external means. The capacity loss is permanent because the metals used in the cells are designated to run for a specific time only and are being consumed during their service life.
  • Chapter 10 Page 6:
    The Li-ion battery has a time clock that starts ticking as soon as the battery leaves the factory. The electrolyte slowly 'eats up' the positive plate and the electrolyte decays. This chemical change causes the internal resistance to increase. In time, the cell resistance raises to a point where the battery can no longer deliver the energy, although it may still be retained in the battery.

    In addition to cycling, the battery ages even if not used. The amount of permanent capacity loss the battery suffers during storage is governed by the SoC and temperature. For best results, keep the battery cool. In addition, store the battery at a 40 percent charge level. Never fully charge or discharge the battery before storage. The 40 percent charge assures a stable condition even if self-discharge robs some of the battery's energy. Most battery manufacturers store Li-ion batteries at 15°C (59°F) and at 40 percent charge.
  • Chapter 10 Page 7:
    Lithium-based batteries have a defined age limit. Once the anticipated cycles have been delivered, no method exists to improve the battery. The main reason for failure is high internal resistance caused by oxidation. Operating the battery at elevated temperatures will momentarily reduce this condition. When the temperature normalizes, the condition of high internal resistance returns.

    The speed of oxidation depends on the storage temperature and the battery's charge state. Keeping the battery in a cool place can prolong its life. The Li-ion battery should be stored at 40 percent rather than full-charge state.

    An increasing number of modern batteries fall prey to the cut-off problem induced by a deep discharge. This is especially evident on Li-ion batteries for mobile phones. If discharged below 2.5V/cell, the internal protection circuit often opens. Many chargers cannot apply a recharge and the battery appears to be dead.
  • Chapter 5 Page 3:
    Lithium-based batteries have a defined age limit. Once the anticipated cycles have been delivered, no method exists to improve the battery. The main reason for failure is high internal resistance caused by oxidation. Operating the battery at elevated temperatures will momentarily reduce this condition. When the temperature normalizes, the condition of high internal resistance returns.

    The speed of oxidation depends on the storage temperature and the battery's charge state. Keeping the battery in a cool place can prolong its life. The Li-ion battery should be stored at 40 percent rather than full-charge state.

    An increasing number of modern batteries fall prey to the cut-off problem induced by a deep discharge. This is especially evident on Li-ion batteries for mobile phones. If discharged below 2.5V/cell, the internal protection circuit often opens. Many chargers cannot apply a recharge and the battery appears to be dead.
  • Chapter 5 Page 5:
    ... a Li-ion performs better at high temperatures. Elevated temperatures temporarily counteracts the battery's internal resistance, which is a result of aging. The energy gain is short-lived because elevated temperature promotes aging by further increasing the internal resistance.
  • Chapter 2 Page 7:
    Despite its overall advantages, Li-ion also has its drawbacks. It is fragile and requires a protection circuit to maintain safe operation. Built into each pack, the protection circuit limits the peak voltage of each cell during charge and prevents the cell voltage from dropping too low on discharge. In addition, the maximum charge and discharge current is limited and the cell temperature is monitored to prevent temperature extremes. With these precautions in place, the possibility of metallic lithium plating occurring due to overcharge is virtually eliminated.

    Aging is a concern with most Li-ion batteries. For unknown reasons, battery manufacturers are silent about this issue. Some capacity deterioration is noticeable after one year, whether the battery is in use or not. Over two or perhaps three years, the battery frequently fails. It should be mentioned that other chemistries also have age-related degenerative effects. This is especially true for the NiMH if exposed to high ambient temperatures.

    Storing the battery in a cool place slows down the aging process of the Li-ion (and other chemistries). Manufacturers recommend storage temperatures of 15°C (59°F). In addition, the battery should only be partially charged when in storage.

    Extended storage is not recommended for Li-ion batteries. Instead, packs should be rotated. The buyer should be aware of the manufacturing date when purchasing a replacement Li-ion battery. Unfortunately, this information is often encoded in an encrypted serial number and is only available to the manufacturer.
  • Chapter 15 Page 2:
    The Li-ion does not like prolonged storage. Irreversible capacity loss occurs after 6 to 12 months, especially if the battery is stored at full charge and at warm temperatures.

    The recommended storage temperature of a lithium-based battery is 15°C (59°F) or less. A charge level of 40 percent allows for some self-discharge that naturally occurs; and 15°C is a practical and economical storage temperature that can be achieved without expensive climate control systems.
  • Chapter 14 Page 1:
    The self-discharge of the Li-ion battery is five percent in the first 24 hours after charge and averages 1 to 2 percent per month thereafter. In addition to the natural self-discharge through the chemical cell, the safety circuit draws as much as 3 percent per month. High cycle count and aging has little effect on self-discharge on lithium-based batteries.
  • Chapter 4 Page 8:
    The charge time of all Li-ion batteries, when charged at a 1C initial current, is about 3 hours. The battery remains cool during charge. Full charge is attained after the voltage has reached the upper voltage threshold and the current has dropped and leveled off at about 3 percent of the nominal charge current.

    Increasing the charge current on a Li-ion charger does not shorten the charge time by much. Although the voltage peak is reached quicker with higher current, the topping charge will take longer. Figure 4-5 shows the voltage and current signature of a charger as the Li-ion cell passes through stage one and two.

    Some chargers claim to fast-charge a Li-ion battery in one hour or less. Such a charger eliminates stage 2 and goes directly to 'ready' once the voltage threshold is reached at the end of stage 1. The charge level at this point is about 70 percent. The topping charge typically takes twice as long as the initial charge.

    No trickle charge is applied because the Li-ion is unable to absorb overcharge. Trickle charge could cause plating of metallic lithium, a condition that renders the cell unstable. Instead, a brief topping charge is applied to compensate for the small amount of self-discharge the battery and its protective circuit consume.
  • Chapter 4 Page 8:
    What if a battery is inadvertently overcharged? Li-ion batteries are designed to operate safely within their normal operating voltage but become increasingly unstable if charged to higher voltages. On a charge voltage above 4.30V, the cell causes lithium metal plating on the anode. In addition, the cathode material becomes an oxidizing agent, loses stability and releases oxygen. Overcharging causes the cell to heat up.
  • Chapter 4 Page 9:
    The Li-ion batteries offer good cold and hot temperature charging performance. Some cells allow charging at 1C from 0°C to 45°C (32°F to 113°F). Most Li-ion cells prefer a lower charge current when the temperature gets down to 5°C (41°F) or colder. Charging below freezing must be avoided because plating of lithium metal could occur.
  • Chapter 5 Page 1:
    Li-ion/polymer batteries are electronically protected against high discharge currents . Depending on battery type, the discharge current is limited somewhere between 1C and 2C. This protection makes the Li-ion unsuitable for biomedical equipment, power tools and high-wattage transceivers. These applications are commonly reserved for the NiCd battery.
  • Chapter 5 Page 3:
    The Li-ion typically discharges to 3.0V/cell. The spinel and coke versions can be discharged to 2.5V/cell. The lower end-of-discharge voltage gains a few extra percentage points. Since the equipment manufacturers cannot specify which battery type may be used, most equipment is designed for a three-volt cut-off.

    Caution should be exercised not to discharge a lithium-based battery too low. Discharging a lithium-based battery below 2.5V may cut off the battery's protection circuit. Not all chargers accommodate a recharge on batteries that have gone to sleep because of low voltage.

    Some Li-ion batteries feature an ultra-low voltage cut-off that permanently disconnects the pack if a cell dips below 1.5V. This precaution prohibits recharge if a battery has dwelled in an illegal voltage state. A very deep discharge may cause the formation of copper shunt, which can lead to a partial or total electrical short. The same occurs if the cell is driven into negative polarity and is kept in that state for a while. A fully discharged battery should be charged at 0.1C. Charging a battery with a copper shunt at the 1C rate would cause excessive heat. Such a battery should be removed from service.
  • Chapter 15 Page 3:
    The internal protection circuit of lithium-based batteries may be the cause of some problems. For safety reasons, many of these batteries do not allow a recharge if the battery has been discharged below 2.5V/cell. If discharged close to 2.5V and the battery is not recharged for a while, self-discharge further discharges the pack below the 2.5V level. If, at this time, the battery is put into the charger, nothing may happen. The battery appears to have an open circuit and the user consequently demands a replacement.
    •    
  • Currently 2.83 / 5
  You rated: 1 / 5 (12 votes cast)
 
[132,288 views]  

An overview of laptop battery technology | 21 comments | Create New Account
Click here to return to the 'An overview of laptop battery technology' hint
The following comments are owned by whoever posted them. This site is not responsible for what they say.
No. of recharge cycles irrelevant?
Authored by: VicF on Mar 21, '03 01:24:51PM

Very useful information. Much gratitude to the poster. A question:

This information repeats many times that age/time by itself deteriorates Li-Ion batteries. My question is, do discharge-recharge cycles ADD to this deterioration, or is the amount of deterioration solely a function of age? Practically speaking, this amounts to asking whether it's worth it at all to avoid unplugging my laptop for short periods of time*, the hope having been that by avoiding a discharge-recharge cycle of any length, I'm prolonging the life of my battery.

* The article does a GREAT job of describing that short discharge-recharge cycles are no worse than long ones.



[ Reply to This | # ]
No. of recharge cycles irrelevant?
Authored by: rameeti on Mar 23, '03 11:57:55AM

I'm not clear on the number of recharge cycles, but... Apple does infer
that continuous or repeated small charge/discharge cycles can impede a
batteries life. Again, in contrast to what this article infers. See the below
for my source on this.

http://docs.info.apple.com/article.html?artnum=88344



[ Reply to This | # ]
No. of recharge cycles irrelevant?
Authored by: Winston on Sep 16, '03 11:51:41AM
The number of full charge cycles is relevant. LiIons are supposed to get about 500 full charge discharge cycles. However because of the natural degradation over time, its more likely that aging will kill the battery than use, although use is a factor. If you constantly charged/discharged the LiIon several times a day you might have a bigger influence from the charge/discharge cycles. The Apple article is consistent with my post. It says: Symptom The battery appears to stop charging between 95 percent and 99 percent. Solution This is normal. The batteries used in these computers are designed to avoid short discharge/charge cycles in order to prolong the overall life of the battery. Because of this, when setting the Mac OS X battery status menu bar icon to display charge state by percentage, you may notice that the reported charge stays between 95 percent and 99 percent. When the battery level eventually drops below 95 percent, it will charge all the way to 100 percent. There are two issues: 1. What the battery monitor says. 2. "short charge/discharge cycles" 1. The battery monitor is only an estimate. If it never gets to 100% it is because the circuit in the battery decided the battery was charged before the battery monitor got to 100%. Apple has instructions for calibrating the battery monitor which basically say charge the computer fully, use it until it goes into forced sleep, then charge it fully again. This resets the computer's battery monitor, but does nothing for the battery 2. The issue is preventing LiIons from overcharging. Once fully charged, they can't be left on "trickle charge" without danger of overcharging. As a result, they have to run down a bit before the battery's charging cycle will let them start being charged again. There may be some issue on very short charges, but the main issue is not overcharging the battery. - Winston

[ Reply to This | # ]
No. of recharge cycles irrelevant?
Authored by: Winston on Sep 16, '03 11:53:38AM
The number of full charge cycles is relevant. LiIons are supposed to get about 500 full charge discharge cycles. However because of the natural degradation over time, its more likely that aging will kill the battery than use, although use is a factor.
If you constantly charged/discharged the LiIon several times a day you might have a bigger influence from the charge/discharge cycles.
The Apple article is consistent with my post. It says:
Symptom
The battery appears to stop charging between 95 percent and 99 percent.
Solution
This is normal. The batteries used in these computers are designed to avoid short discharge/charge cycles in order to prolong the overall life of the battery. Because of this, when setting the Mac OS X battery status menu bar icon to display charge state by percentage, you may notice that the reported charge stays between 95 percent and 99 percent. When the battery level eventually drops below 95 percent, it will charge all the way to 100 percent.

There are two issues: 1. What the battery monitor says. 2. "short charge/discharge cycles"
1. The battery monitor is only an estimate. If it never gets to 100% it is because the circuit in the battery decided the battery was charged before the battery monitor got to 100%. Apple has instructions for calibrating the battery monitor which basically say charge the computer fully, use it until it goes into forced sleep, then charge it fully again. This resets the computer's battery monitor, but does nothing for the battery
2. The issue is preventing LiIons from overcharging. Once fully charged, they can't be left on "trickle charge" without danger of overcharging. As a result, they have to run down a bit before the battery's charging cycle will let them start being charged again. There may be some issue on very short charges, but the main issue is not overcharging the battery.

- Winston

[ Reply to This | # ]
An overview of laptop battery technology
Authored by: merlyn on Mar 21, '03 02:03:51PM

Although it doesn't undermine the veracity of the posted article, the "nicad memory effect" is a myth, perpetrated by the battery manufacturers for the most part. Google around for the stories... it's pretty amazing.

Sure, Nicads wore out, and you could accelerate that by overcharging, but "fully draining" them was never the proper solution except for the earliest "timed" chargers rather than the later charge-sensitive chargers.



[ Reply to This | # ]
An overview of laptop battery technology
Authored by: Winston on Sep 16, '03 12:27:21PM
You might want to read what the Buchmann site says about memory effect on NiCads and NiMh batteries. There is a lot of detail about what goes on chemically and the various charging methods available:
http://www.buchmann.ca

It does appear that there is a memory effect for NiCads and NiMh batteries.


- Winston

[ Reply to This | # ]
An overview of laptop battery technology
Authored by: vonleigh on Mar 21, '03 08:43:21PM

So basically our ipods will be useless in about 3 years? I don't think one can purchase batteries for them; so I guess it will be left to the tinkerers to do these mods.



[ Reply to This | # ]
An overview of laptop battery technology
Authored by: WelshDog on Mar 23, '03 05:54:34PM
Yes, true. This is why I don't have one. I refuse to pay 300+ bucks for something I will throw away to 2-3 years. It's not just the battery either. The hard drive has a pretty short life expectancy as well. Apple might have some serious PR troubles in a year or so.
So basically our ipods will be useless in about 3 years? I don't think one can purchase batteries for them; so I guess it will be left to the tinkerers to do these mods.

[ Reply to This | # ]
An overview of laptop battery technology
Authored by: paploo on Mar 24, '03 02:28:47AM

After having my first rev iPod for just under a year, the battery life shortened to 4 hours. (Although I wonder how much of that is related to the bad battery routines that were just fixed in the latest patches?). Fortunately, I got the 1-year warranty at CompUSA, so I got to upgrade to a brand new iPod (which had come out a few weeks before) for free. :) (I should note that when I got the second one, the warranty covers it for *two* years. Something better break just before that, so that I get a new one again. :) And people say CompUSA isn't good for anything. :) )



[ Reply to This | # ]
An overview of laptop battery technology
Authored by: creus on May 17, '03 05:54:07PM
You can get replacement batteries for ipods here: http://www.ipodbattery.com/

[ Reply to This | # ]
An overview of laptop battery technology
Authored by: rameeti on Mar 22, '03 10:43:07AM

I love information. Thanks to the writer for sharing it. But...

The continuous repetition of the same information over and over shows
the beginnings of a writers life which brings into consideration the
accuracy of the information.

i.e. The article says that the Li-Ion battery should not be run completely
down yet Apple's reccommendation is to the contrary. See the bottom of


And note that Apple's 17" pdf recommends running it all the way down
immediately upon receipt. It also says that you can run it down at your
leisure after that. And finally, it says that you should store the battery at
100% which is complete contrast to this article's 40% that is repeated
over and over and over. I'm thinking that Apple has greater expertise in
this area and that Apple's desire for user's pleasure of experience with
the batteries exceeds any thoughts of making money from selling
replacments.


Do others think I'm way off base on this?



[ Reply to This | # ]
An overview of laptop battery technology
Authored by: rameeti on Mar 22, '03 10:46:35AM

Somehow my links got dropped from my previous post.

<http://developer.apple.com/techpubs/hardware/Developer_Notes/<
Macintosh_CPUs-G4/PowerBookG4_17inch/PowerBookG417inch.pdf>

<http://docs.info.apple.com/article.html?artnum=10970>



[ Reply to This | # ]
An overview of laptop battery technology
Authored by: Winston on Sep 16, '03 12:14:39PM
Apple's main issue is having the menu bar battery meter be approximately right about the remaining battery life. The initial procedure of charging and then fully discharging is designed to set the battery meter. It has nothing to do with the battery life itself.

see:
http://docs.info.apple.com/article.html?artnum=86284


- Winston

[ Reply to This | # ]
An overview of laptop battery technology
Authored by: Winston on Sep 16, '03 12:21:52PM
The continuous repetition of the same information over and over shows the beginnings of a writers life which brings into consideration the accuracy of the information.

I agree that Mr. Buchmann is a bit wordy, but if you go to his site and look at the info he has collected I think you will find it convincing. The passages I selected each have a new thought or clarification. I chose to quote Buchmann directly (with the exception of my summary at the top) as this was the source for most, although not all, of my information. It's there for those who wanted to know more detail, but did not want to wade through Buchmann's site.

- Winston

[ Reply to This | # ]
Missing links for above comment
Authored by: rameeti on Mar 22, '03 10:48:56AM

Somehow my links got dropped from my previous post.

<http://developer.apple.com/techpubs/hardware/Developer_Notes/<
Macintosh_CPUs-G4/PowerBookG4_17inch/PowerBookG417inch.pdf>

<http://docs.info.apple.com/article.html?artnum=10970>



[ Reply to This | # ]
3 years and longer...
Authored by: flx on Mar 22, '03 12:23:19PM

my mobile phone runs on a liIon batterie for 7 years now. Still with good standby time (can hardly tell the difference from when it was new).

flx



[ Reply to This | # ]
An overview of laptop battery technology
Authored by: 010111 on Mar 22, '03 05:04:36PM

i thought the 17" didn't use plain old litium-ion batteries anymore (the 12" and 15" still do though...) they use "lithium-ion prismatic" ... anyone know the difference between the two?



[ Reply to This | # ]
An overview of laptop battery technology
Authored by: coyote on Mar 23, '03 06:30:41PM

Here is some information on 'lithium ion prismatic' batteries:

http://www.ulbi.com/product-display.asp?ID=47

coyote

[ Reply to This | # ]

An overview of laptop battery technology
Authored by: tim ryan on Jun 18, '03 01:32:53PM

sorry,nothing spectacular here....prismatic refers to shape of battery...flat and thin rectangular



[ Reply to This | # ]
An overview of laptop battery technology
Authored by: nnewton on Sep 03, '03 05:20:30PM

The lithium prismatic battery is just made with lithium prismatic cells AKA square or rectangle cells to conserve space or for style. You will find that they carry a variety of capacities but are most generally less capacity than standard cylindrical cells used in most batteries.
Most cell phone batteries are made with prismatic liion cells now...Also, The 'battery regulators' in lithium batteries nowadays are made to regulate charge&discharge and sometimes to talk to the computer on state of charges. You should not worry to much about the cycles (usually 250-750 is industry standard) since the battery may act weird due to the regulator protecting the cells. If your battery isnt working well, just run it dead twice and charge it-you may find it will work better the next dozen cycles...2-3 years is standard. It will have a shelf life charged of 5-7 years. But remember that by the time it reaches a consumer the battery has already aged a year...Most manufaturers use decent cells so shop price from reputable online companies for a deal...

please reply with any FAQ's



[ Reply to This | # ]
An overview of laptop battery technology
Authored by: TRU on Sep 30, '06 07:12:29PM

THERE IS A COMPLETELY SAFE LAPTOP BATTERY TECHNOLOGY
The Li-Fiber cell is completely safe and with $1 million the company can produce enough cells to prove that it has a laptop battery that is not only completely safe but also outperforms all existing laptop batteries. The 2006 massive recall by DELL, Apple, IBM, Toshiba, Panasonic, Fujitsu and Lenovo of over 7 million notebook computer batteries made by Sony would be a thing of the past. The present lithium-ion battery is an almost zero tolerance technology, prone to failure, over heat, fire, and even explosion; hence the need for protection circuits. The higher the cell capacity the more serious the problem. For high capacity multi-cell high voltage batteries, for example, 10 Ah, 200 V for hybrid electric vehicles HEV's, inherently safe battery chemistry is essential but cannot be met with conventional Li-Ion cells. The Li-Fiber battery does not overheat and makes a very good safe high performance [yet cheaper] laptop and power tool batteries. Contact me Edward Anderson at TRU Group Inc if you have $1 million to invest.



[ Reply to This | # ]