li-ion battery

On Tue, 7 Nov 2006 02:52:03 -0600, "BillW50" <[email protected]> wrote:

>"Deodiaus" <[email protected]> wrote in message
>news:[email protected]
>> The guy who suggested connecting it to a high voltage source was my
>> lab techie.
>> I did see the video of the exploding laptop, but think it is a fake.
>> There is just way too much flame for a battery like that, and the
>> crowd in the background just stands around watching it. With flames
>> like that, I'd be running for the fire hydrant.
>> I use to make home made gun powder and bottle rockets as a kid, so its
>> hard to fool me.
>
>No, don't do it! Once the Li-Ion battery drops to a low level, Li-Ion
>battery chargers are made to not charge the battery. Because if they
>did, they can explode.

That advice is actually contrary to widespread design practice. Once a cell
goes below the safe cutoff voltage, most "intelligent" chargers actually attempt
a low current charge which is actually safe and (unless the cell is actually
faulty) will progressively bring the cell voltage back up to the point where
normal charging can continue.

The unsafe practice with Li-xx is overvoltage. Attempts to charge these cells
(either from a normal or low voltage staring point) need to be carried out with
a proper charger OR by someone who understands their care-and-feeding and takes
the necessary precautions.

The unwise practice is to leave a cell in an undervoltage condition, as
irreversible degradation occurs.

>It just isn't worth the risk.

I'm not aware of undervoltage Li-xx cells exploding. Can you cite any
reference(s)?

---

› See More: li-ion battery

budgie <[email protected]> wrote in news:t0v0l2to90k4lgncg3q3oork3hrt1o78io@
4ax.com:

> The unwise practice is to leave a cell in an undervoltage condition, as
> irreversible degradation occurs.
>
>

This is an excellent statement. Battery users got used to the Ni-Cd memory
problems and got used to the total-discharge-them-to-prevent-memory
scenario. When they migrated to Li-Ion, noone told them Li-Ions should be
immediately recharged, NO MATTER WHAT THEIR CHARGE STATE...just like lead-
acid float batteries.

So, the cellphone users sleeping right next to their chargers, don't plug
the phones in at night until they are nearly dead, causing premature
battery failures that could have easily been prevented by simply plugging
the phone in next to their beds. If you never discharge them below 80%,
easy to do in most cellphones, Li-Ion batteries will last for years, making
battery salesmen and manufacturers quite unhappy.

They all seem so proud of how long they can make them run before plugging
them in. How silly....

Larry
--
Halloween candy left over.....
Is there a downside?

Larry wrote:
>
> Halloween candy left over.....
> Is there a downside?


Diabetes.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

"budgie" <[email protected]> wrote in message
news:[email protected]
> On Tue, 7 Nov 2006 02:52:03 -0600, "BillW50" <[email protected]> wrote:
>
>> "Deodiaus" <[email protected]> wrote in message
>> news:[email protected]
>>> The guy who suggested connecting it to a high voltage source was my
>>> lab techie.
>>> I did see the video of the exploding laptop, but think it is a fake.
>>> There is just way too much flame for a battery like that, and the
>>> crowd in the background just stands around watching it. With flames
>>> like that, I'd be running for the fire hydrant.
>>> I use to make home made gun powder and bottle rockets as a kid, so
>>> its hard to fool me.
>>
>> No, don't do it! Once the Li-Ion battery drops to a low level, Li-Ion
>> battery chargers are made to not charge the battery. Because if they
>> did, they can explode.
>
> That advice is actually contrary to widespread design practice. Once
> a cell goes below the safe cutoff voltage, most "intelligent"
> chargers actually attempt a low current charge which is actually safe
> and (unless the cell is actually faulty) will progressively bring the
> cell voltage back up to the point where normal charging can continue.
>
> The unsafe practice with Li-xx is overvoltage. Attempts to charge
> these cells (either from a normal or low voltage staring point) need
> to be carried out with a proper charger OR by someone who understands
> their care-and-feeding and takes the necessary precautions.
>
> The unwise practice is to leave a cell in an undervoltage condition,
> as irreversible degradation occurs.
>
>> It just isn't worth the risk.
>
> I'm not aware of undervoltage Li-xx cells exploding. Can you cite any
> reference(s)?

Just from this guy:

From: "M.I.5¾" <[email protected]_SPAM.co.uk>
Newsgroups: comp.sys.laptops

The company he works for they explode Li-Ion on purpose.

--
Bill

"Larry" <[email protected]> wrote in message
news:[email protected]
> This is an excellent statement. Battery users got used to the Ni-Cd
> memory problems and got used to the
> total-discharge-them-to-prevent-memory scenario. When they migrated
> to Li-Ion, noone told them Li-Ions should be immediately recharged,
> NO MATTER WHAT THEIR CHARGE STATE...just like lead- acid float
> batteries.
[snip]

I agree Larry. Although laptop Li-Ion batteries seem to act differently.
Tons of people have learned for you leave them in the charger 24/7 (in
the laptop under AC power), the battery is usually worthless in about 2
years (even though you never used it). Brand doesn't matter.

But if you leave them out of the laptop and just recharge them about
once every 6 months, they can last 10 years or more. Some of us have
theories why this happens. And most of us believe it is do to the fact
that laptops usually get pretty hot and slowly destroys them.

--
Bill

BillW50 wrote:

> I agree Larry. Although laptop Li-Ion batteries seem to act differently.
> Tons of people have learned for you leave them in the charger 24/7 (in
> the laptop under AC power), the battery is usually worthless in about 2
> years (even though you never used it). Brand doesn't matter.
>
> But if you leave them out of the laptop and just recharge them about
> once every 6 months, they can last 10 years or more. Some of us have
> theories why this happens. And most of us believe it is do to the fact
> that laptops usually get pretty hot and slowly destroys them.


It may also be caused by high voltage. Increasing voltage by 1/10th of a
volt stores decidedly more power in the battery, but also makes the life
a lot shorter. It can be inferred that topping the battery up to full
charge is bad for it.

My ancient laptop always charges the battery whenever it has been
unplugged for a while.

My new laptop only starts charging whenever there is a real amount of
discharge. If there is none, the charge light does not come on.

The cells are now at 4.187 volts, which is slightly below the voltage
they reach at end of charge. But it is still high, I must say. I'll
check if it goes down a bit with time.


Thomas

On Tue, 7 Nov 2006 11:20:21 -0600, "BillW50" <[email protected]> wrote:

>"Larry" <[email protected]> wrote in message
>news:[email protected]
>> This is an excellent statement. Battery users got used to the Ni-Cd
>> memory problems and got used to the
>> total-discharge-them-to-prevent-memory scenario. When they migrated
>> to Li-Ion, noone told them Li-Ions should be immediately recharged,
>> NO MATTER WHAT THEIR CHARGE STATE...just like lead- acid float
>> batteries.
>[snip]
>
>I agree Larry. Although laptop Li-Ion batteries seem to act differently.
>Tons of people have learned for you leave them in the charger 24/7 (in
>the laptop under AC power), the battery is usually worthless in about 2
>years (even though you never used it). Brand doesn't matter.
>
>But if you leave them out of the laptop and just recharge them about
>once every 6 months, they can last 10 years or more. Some of us have
>theories why this happens. And most of us believe it is do to the fact
>that laptops usually get pretty hot and slowly destroys them.

It is a combination of two factors.

Heat is the main one - while the laptop is running there is substantial heat
which reaches the battery bay. Careful design can minimise this, but the
pressure to jam more functionality into ever thinner (i.e. volumetrically
smaller) boxes usually negates this effort. Use of external AC/DC power packs
removes one heat source, but there are many - the CPU and HDD being the main
two.

Cell degradation is a function of cell voltage, and maintaining cell voltage at
the charge termination figure will accelerate its demise. Sensible charging
regimes ensure that once a pack has reached the charge termination voltage, no
further attempt is made to charge it until the voltage drops by a noticeable
amount. For example, using a 4v20 cutoff, charge reinitiation at 3v95 is often
employed in industrial (non-laptop) applications where the pack remains
connected to the charger.

Also the commercial pressures in the laptop market result in the use of
termination voltages at the high end of the recommended range. Dropping from
4v20 to 4v10 loses noticeable capacity, but would certainly extend battery pack
life significantly. To the manufacturer/vendor, that isn't good business. To
the user who pays the life cycle owning cost, it would be a great decision.

On Tue, 07 Nov 2006 20:59:54 +0100, Zak <[email protected]> wrote:

>BillW50 wrote:
>
>> I agree Larry. Although laptop Li-Ion batteries seem to act differently.
>> Tons of people have learned for you leave them in the charger 24/7 (in
>> the laptop under AC power), the battery is usually worthless in about 2
>> years (even though you never used it). Brand doesn't matter.
>>
>> But if you leave them out of the laptop and just recharge them about
>> once every 6 months, they can last 10 years or more. Some of us have
>> theories why this happens. And most of us believe it is do to the fact
>> that laptops usually get pretty hot and slowly destroys them.
>
>
>It may also be caused by high voltage. Increasing voltage by 1/10th of a
>volt stores decidedly more power in the battery, but also makes the life
>a lot shorter. It can be inferred that topping the battery up to full
>charge is bad for it.

Exactly.

>My ancient laptop always charges the battery whenever it has been
>unplugged for a while.

Assuming it is Li-XX, that is not clever at all.

>My new laptop only starts charging whenever there is a real amount of
>discharge. If there is none, the charge light does not come on.

They are starting to improve things.

>The cells are now at 4.187 volts, which is slightly below the voltage
>they reach at end of charge. But it is still high, I must say. I'll
>check if it goes down a bit with time.

I sincerely wish the user had the choice to lower the charge termination voltage
from 4v20 to 4v10. I for one would certainly go for the lifetime-vs-endurance
tradeoff that causes.

"budgie" <[email protected]> wrote in message
news:[email protected]
[snip]
> I sincerely wish the user had the choice to lower the charge
> termination voltage from 4v20 to 4v10. I for one would certainly go
> for the lifetime-vs-endurance tradeoff that causes.

You can! Buy or build your own programable charger. I bought one for
about $125.

--
Bill

Larry wrote:
> budgie <[email protected]> wrote in news:t0v0l2to90k4lgncg3q3oork3hrt1o78io@
> 4ax.com:
>
>> The unwise practice is to leave a cell in an undervoltage condition, as
>> irreversible degradation occurs.
>>
>>
>
> This is an excellent statement. Battery users got used to the Ni-Cd memory
> problems and got used to the total-discharge-them-to-prevent-memory
> scenario. When they migrated to Li-Ion, noone told them Li-Ions should be
> immediately recharged, NO MATTER WHAT THEIR CHARGE STATE...just like lead-
> acid float batteries.

Actually this is incorrect either. High voltages accelerate reaction
between electrolyte and anode. That is why charging cells regularly to
4.1V instead of 4.2V prolongs their cycle life by 30% (this is widely
used in back-up systems).

Li-ion is unlike any battery. It does not like either full charge or
full discharge. It likes to be left alone
in some intermediate charge state. That is why the cells are shipped in 50%
state of charge.

It is not harmful to discharge them to full (it does not cause by itself
any damage, unlike lead-acid case) as long as you recharge it soon afterwards.

> So, the cellphone users sleeping right next to their chargers, don't plug
> the phones in at night until they are nearly dead, causing premature
> battery failures that could have easily been prevented by simply plugging
> the phone in next to their beds. If you never discharge them below 80%,
> easy to do in most cellphones, Li-Ion batteries will last for years, making
> battery salesmen and manufacturers quite unhappy.

That is not true, as there is no evidence of any improvement of cycle life
between cycling from 100 to 20% compared to 100 to 0.
At the other hand, there is a clear evidence that at high voltages degradation
is faster.

What IS harmful is discharging is living battery in discharged state for long
periods of time, because self-discharge and electronic load will overdischarge
them into low voltage areas below 3V open circuit voltage (OCV) where
corrosion of Cu-current collectors can happen.
Note that "OCV" and voltage under load are different things. If under C/2
load you stop discharging at 3V, voltage will rapidly relax to 3.5V OCV because
most of low voltage is caused by IR drop.
But if you see actual open circuit voltage of 3V, cell is over discharged.

Regards,
EVgenij

>
> They all seem so proud of how long they can make them run before plugging
> them in. How silly....
>
> Larry

Zak wrote:

> The cells are now at 4.187 volts, which is slightly below the voltage
> they reach at end of charge. But it is still high, I must say. I'll
> check if it goes down a bit with time.

That was yesterday. Today the voltage has gone down a bit more, to 4.182
volts. I don't know if that looks like a cell under no load, but I hope so.


Thomas

On Wed, 8 Nov 2006 09:58:26 -0600, "BillW50" <[email protected]> wrote:

>"budgie" <[email protected]> wrote in message
>news:[email protected]
>[snip]
>> I sincerely wish the user had the choice to lower the charge
>> termination voltage from 4v20 to 4v10. I for one would certainly go
>> for the lifetime-vs-endurance tradeoff that causes.
>
>You can! Buy or build your own programable charger. I bought one for
>about $125.

I really meant on my laptop collection .....

(I have designed a commercially successful charger which had selectable
termination voltage).

"Evgenij Barsukov" <[email protected]> wrote in message
news:[email protected]

[...]
> Actually this is incorrect either. High voltages accelerate reaction
> between electrolyte and anode. That is why charging cells regularly to
> 4.1V instead of 4.2V prolongs their cycle life by 30% (this is widely
> used in back-up systems)...

Do you have any idea that some of us are getting 10 years and more on
our Li-Ion batteries? It isn't much of a secret, we are just lazy. lol

I have to tell you that you are on the right track though. I mean you
are really close. I have not much to disagree with you, but you are not
there yet.

--
Bill

BillW50 wrote:
> "Evgenij Barsukov" <[email protected]> wrote in message
> news:[email protected]
>
> [...]
>> Actually this is incorrect either. High voltages accelerate reaction
>> between electrolyte and anode. That is why charging cells regularly to
>> 4.1V instead of 4.2V prolongs their cycle life by 30% (this is widely
>> used in back-up systems)...
>
> Do you have any idea that some of us are getting 10 years and more on
> our Li-Ion batteries? It isn't much of a secret, we are just lazy. lol

Because main reason of usable capacity loss for Li-ions is its impedance
increase and NOT the loss of available material, you might use the cell
quite long if your application draws low currents such as below C/5 rate.

Not charging to full 4.2V and keeping it cold (for example by removing
it from the laptop when used as PC) can also increase life noticeably.

Btw Li-ion battery is in mass production for barely more than 10 years (it
was released in 1990). Initially Sony cells was the only game in town.
You are telling me that you got your cells in 1996 and they are still alive?
What is the useable capacity compared to design capacity?

Regards,
Yevgen

"Evgenij Barsukov" <[email protected]> wrote in message
news:[email protected]
> BillW50 wrote:
>> "Evgenij Barsukov" <[email protected]> wrote in message
>> news:[email protected]
>>
>> [...]
>>> Actually this is incorrect either. High voltages accelerate reaction
>>> between electrolyte and anode. That is why charging cells regularly
>>> to 4.1V instead of 4.2V prolongs their cycle life by 30% (this is
>>> widely used in back-up systems)...
>>
>> Do you have any idea that some of us are getting 10 years and more on
>> our Li-Ion batteries? It isn't much of a secret, we are just lazy.
>> lol
>
> Because main reason of usable capacity loss for Li-ions is its
> impedance increase and NOT the loss of available material, you might
> use the cell quite long if your application draws low currents such
> as below C/5 rate.
> Not charging to full 4.2V and keeping it cold (for example by removing
> it from the laptop when used as PC) can also increase life noticeably.
>
> Btw Li-ion battery is in mass production for barely more than 10
> years (it was released in 1990). Initially Sony cells was the only
> game in town. You are telling me that you got your cells in 1996 and
> they are still
> alive? What is the useable capacity compared to design capacity?
>
> Regards,
> Yevgen

Yes I do have Li-ion batteries this old. They are cell phone batteries
though. And I don't use them anymore. But I still charge them up about
once a year. I haven't checked their capacity in a few years. But I do
know they did have 50% or better still left just a year or two ago.

My Palm IIIc Li-Ion battery lasted 5 years. And I just replaced it. And
the last 6 months of its life, I had it on the charger 24/7 (it's
automatic and will kickoff and on when needed). And I believe this is
what killed it. Yet the charger only charges it up to 4.10 volts. And
you can't turn these things off. It runs for about 2 weeks in standby or
about 12 hours up and running. And I run it down to only 50% before I
recharge it.

I have very good luck only draining Li-Ion batteries down to about 40 to
50% and then recharging them. Either by use, or by self discharge.

I have 4 six year old laptop batteries. Two were left in the machines
being charged and hardly ever used. They died just over two years. The
other two had some experience being left in on charge for a few months.
The one that spent the most time on charge is down 40% of capacity. The
other one which rarely ever spent time in the charger only has lost 20%.

The weird thing is, with cell phones... keeping them on the charger
seems to make them last long. But for Palms and laptops, avoiding the
charger seems to be best.

--
Bill