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Li-Ion Shelf Life: Outdated? Daveman750 08-27-2006
Posted by Daveman750 on August 27, 2006, 10:42 pm
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 My understanding from extensive reading that I have done on the subject
is that Li-Ion batteries have a finite, relatively short shelf life,
even when not in use. However, it seems from personal experience that
this is simply not true. I have purchased two separate CompUSA
Amerinote AN laptops from 1999 or 2000 on Ebay, and both came with
working Li-Ion batteries that held charges. I am not sure of the
history of these laptops, but I do know that most likely these were the
original batteries, as new replacements are almost impossible to find.
I also purchased a used Dell C600 laptop that was apparently 4 years
old, and it gets approximately 2 hours of battery life.

Does anyone else have similar experiences? Is it possible that, while
at one time Li-Ion batteries did have limited shelf life, the chemistry
was improved years ago and we are just starting to see the effects of
these improvements now that those batteries are starting to age?


Posted by zwsdotcom on August 27, 2006, 10:49 pm
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Daveman750 wrote:
> My understanding from extensive reading that I have done on the subject
> is that Li-Ion batteries have a finite, relatively short shelf life,

The shelf life is heavily influenced by a variety of factors. Some
batteries have an internal microcontroller that leeches a little power
off the pack to keep itself alive. These batteries will discharge past
the safety limit if they are stored for prolonged periods at a low
state of charge. Temperature is a big factor, too.

If your laptop has a calibration utility, use it to recalibrate your
battery capacity. Read out the measured mAh capacity and compare it
with the battery data plate.

The laptop I'm using to type this has two batteries, one of which is
about 18 months old, the other of which is unknown (since I bought this
battery used on eBay). Both of them run the machine for more than three
hours with brightness down and WiFi off. This is about 80% of the
capacity the original battery had when I bought the machine. I consider
this very lucky. On the flipside, my Armada M300's battery went
virtually unused for a year - then I went on a trip, turned the machine
on, and it died suddenly within ten minutes.


Posted by BMonroe(nospam) on August 27, 2006, 11:12 pm
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Actually, Lithium batteries of all kinds have the longest life of any
battery chemical system.

As for Lithium ion rechargeable batteries in particular, they can last a
decade with proper care (which, among other things, requires SOME use
and charging). I service laptopns and have dozens that were made in
1995-1997 that are still nearly as good as new.

Lithium batteries have a limited number of charge-discharge cycles. The
number varies, but it's in the mid hundreds (and I'm not sure how
partial cycles figure into this).

Also, these batteries must not be discharged below a lower threshold,
and deep discharges shorten their life.

Finally, they don't like overcharging and they don't like heat. Various
laptops designs all impinge on these areas to give either long or short
battery life; so a given charging circuit design might or might not
prevent overcharging, a given power monitoring design might or might not
prevent deep discharging, and a given overall laptop design might or
might not minimize exposure to heat (heat generated not by the battery
but by other components of the laptop).

The most conservative advice is to remove the battery when it's not in
use, when the laptop is going to be plugged into the wall for days or
longer. But however you do it, if you take care of the battery, and if
your actual use (cycles) doesn't get into the mid hundreds, they can
last for a very long time. Conversely, take a laptop that exposes the
battery to heat, whose charging design overcharges the battery (which
produces internal heat), and which allows the battery to become deeply
discharged, and you cancreate a situation in which a battery is
essentially destroyed in 6 months or so.


Daveman750 wrote:

> My understanding from extensive reading that I have done on the subject
> is that Li-Ion batteries have a finite, relatively short shelf life,
> even when not in use. However, it seems from personal experience that
> this is simply not true. I have purchased two separate CompUSA
> Amerinote AN laptops from 1999 or 2000 on Ebay, and both came with
> working Li-Ion batteries that held charges. I am not sure of the
> history of these laptops, but I do know that most likely these were the
> original batteries, as new replacements are almost impossible to find.
> I also purchased a used Dell C600 laptop that was apparently 4 years
> old, and it gets approximately 2 hours of battery life.
>
> Does anyone else have similar experiences? Is it possible that, while
> at one time Li-Ion batteries did have limited shelf life, the chemistry
> was improved years ago and we are just starting to see the effects of
> these improvements now that those batteries are starting to age?
>

Posted by M.I.5¾ on August 29, 2006, 2:59 am
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> Actually, Lithium batteries of all kinds have the longest life of any
> battery chemical system.
>
> As for Lithium ion rechargeable batteries in particular, they can last a
> decade with proper care (which, among other things, requires SOME use and
> charging). I service laptopns and have dozens that were made in 1995-1997
> that are still nearly as good as new.
>

Lithium-ion type batteries have the lowest self discharge rate of any
rechargeable chemistry and thus will hold a useable charge for much longer
when kept in storage. However, they also have the lowest number of
charge/discharge cycles of any recognised chemistry, when each is used under
ideal conditions.

> Lithium batteries have a limited number of charge-discharge cycles. The
> number varies, but it's in the mid hundreds (and I'm not sure how partial
> cycles figure into this).
>

The life is full charge/discharge. So a battery that lasts (say) 400 cycles
will last for 800 cycles if the battery is only half discharged each time.
There is no memory effect at all with this chemistry.

> Also, these batteries must not be discharged below a lower threshold, and
> deep discharges shorten their life.
>

Cells should not be discharged below 3.0 volts per cell (2.5 volts for some
early chemistries). In practice, most equipment sets the cut off point at
3.2 volts to gove a margin for error. Discharging Li-ion all the way down
to 3.0 volts does no harm at all as long as the cell is charged more or less
immediately. Discharge below the minimum point causes the cell to plate out
copper on the internal structure which provides a discharge path that
circumvents the PTC protection.

> Finally, they don't like overcharging and they don't like heat. Various
> laptops designs all impinge on these areas to give either long or short
> battery life; so a given charging circuit design might or might not
> prevent overcharging, a given power monitoring design might or might not
> prevent deep discharging, and a given overall laptop design might or might
> not minimize exposure to heat (heat generated not by the battery but by
> other components of the laptop).
>

Heating a battery up shortens its life. In fact storing it at 5°C will make
it last longer than storing it at 20°C. Overcharging a battery causes it to
develop so much heat, it will burst into flame. A property designed charger
will *never* overcharge a Li-ion battery - just as well, as overcharging
causes lithium metal to be deposited on the plates and oxygen gas to be
liberated. The two together cause spontaneous combustion igniting the
highly flammable electrolyte.

> The most conservative advice is to remove the battery when it's not in
> use, when the laptop is going to be plugged into the wall for days or
> longer. But however you do it, if you take care of the battery, and if
> your actual use (cycles) doesn't get into the mid hundreds, they can last
> for a very long time. Conversely, take a laptop that exposes the battery
> to heat, whose charging design overcharges the battery (which produces
> internal heat), and which allows the battery to become deeply discharged,
> and you cancreate a situation in which a battery is essentially destroyed
> in 6 months or so.
>

The advice for long life is indeed to remove the battery when running from
AC and you are not actually charging it. As you note, it is the heat from
other parts that causes the problems, though some laptop designs don't have
any heat producing parts near the battery. Battery life is officially 300
charge/discharge cycles, but modern designs of battery now seem to be well
exceeding this. The one thing Li-ion batteries don't like is inactivity.
It is important that they do get discharged and charged periodically.
Properly cared for, a Li-ion battery can last over a decade - I have several
examples, some of very early designs (nobody has one that is 20 years old
yet as the technology hasn't been around that long).

The actual life limiting factors seem to be a closely guarded secret among
the battery manufacturers. Many articles speculate on the factors from
scraps of information acquired (even quoting numbers in some cases- rarely
agreeing). None of them can be regarded as authoritative, especially as
most of the numbers quoted preclude a battery lasting for 10 years.



Posted by Mike S. on August 28, 2006, 9:50 am
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>My understanding from extensive reading that I have done on the subject
>is that Li-Ion batteries have a finite, relatively short shelf life,
>even when not in use. However, it seems from personal experience that
>this is simply not true. I have purchased two separate CompUSA
>Amerinote AN laptops from 1999 or 2000 on Ebay, and both came with
>working Li-Ion batteries that held charges. I am not sure of the
>history of these laptops, but I do know that most likely these were the
>original batteries, as new replacements are almost impossible to find.
>I also purchased a used Dell C600 laptop that was apparently 4 years
>old, and it gets approximately 2 hours of battery life.
>
>Does anyone else have similar experiences? Is it possible that, while
>at one time Li-Ion batteries did have limited shelf life, the chemistry
>was improved years ago and we are just starting to see the effects of
>these improvements now that those batteries are starting to age?

I've experienced both ends of the spectrum with laptop and cellular phone
batteries. Some seem to last forever, and others lose capacity
dramatically after a couple of years. The cobalt-based cells used in these
applications develop increasing internal resistance over time due to
oxidation; this is one reason why cool storage (and avoiding overheating
while actually in service) will prolong the service life.




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