li-ion battery

Evgenij Barsukov wrote:
> 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

We have a 7200 Wh (yes, really, 1008 2.0Ah 18650 cells) Li-ion battery
that I have been maintaining since 2002. It is for an occasional use
project. I cycle it and balance the cells once a year, and then leave
it at 50% state of charge. So far it has held close to its original
capacity at the C/20 rate.

Some of the other batteries we use have shown increases in impedance in
just a couple of years. In one case we had a pair of units,
manufactured at the same time and operated by the same outfit, returned
for evaluation after 2 years of use; one unit had like-new batteries,
the other showed 20% loss of capacity due to increased impedance, and
both units had similar numbers of battery cycles (according to the
internal counter). I think, but don't know, that the higher impedance
unit had been stored at full charge, and or at elevated temperature.

--
NOTE: to reply, remove all punctuation from email name field

Ned Forrester [email protected] 508-289-2226
Applied Ocean Physics and Engineering Dept.
Oceanographic Systems Lab http://adcp.whoi.edu/
Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA

---

› See More: li-ion battery

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.
:
: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

Li-on batteries degrade more quickly when fully charged. I try not to
fully charge mine, therefore. If I do fully charge them, I try to take a
little charge off quickly.

I believe the self degradation of these batteries is lowest at around a
40% charge, and if you don't intend to use them for a while, refrigerate
them at this charge level. That's the way I store my video camera
batteries, since I use them very occasionally.

Even if you take the best care of them, they won't last indefinitely. I
figure if you get 3+ years out of one, you are doing well. Typical usage
I believe is maybe 2 years.

I learned this stuff by checking out the newsgroup:

sci.chem.electrochem.battery

Do www.groups.google.com search on this newsgroup and li-on and battery
life, etc.

Dan

"Dan_Musicant" <[email protected]> wrote in message
news:[email protected]
> 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.
>>
>> 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
>
> Li-on batteries degrade more quickly when fully charged. I try not to
> fully charge mine, therefore. If I do fully charge them, I try to
> take a little charge off quickly.
>
> I believe the self degradation of these batteries is lowest at around
> a 40% charge, and if you don't intend to use them for a while,
> refrigerate them at this charge level. That's the way I store my
> video camera batteries, since I use them very occasionally.
>
> Even if you take the best care of them, they won't last indefinitely.
> I figure if you get 3+ years out of one, you are doing well. Typical
> usage I believe is maybe 2 years.
>
> I learned this stuff by checking out the newsgroup:
>
> sci.chem.electrochem.battery
>
> Do www.groups.google.com search on this newsgroup and li-on and
> battery life, etc.
>
> Dan

Why is it that people who claims to have knowledge about care for Li-Ion
batteries also claim of keeping them alive for only 3 years, while
others ignore this care and feeding and are getting 10 years and
counting with ours?

--
Bill

On Sun, 3 Dec 2006 08:26:24 -0600, "BillW50" <[email protected]> wrote:

:"Dan_Musicant" <[email protected]> wrote in message
:news:[email protected]
:> 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.
:>>
:>> 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
:>
:> Li-on batteries degrade more quickly when fully charged. I try not to
:> fully charge mine, therefore. If I do fully charge them, I try to
:> take a little charge off quickly.
:>
:> I believe the self degradation of these batteries is lowest at around
:> a 40% charge, and if you don't intend to use them for a while,
:> refrigerate them at this charge level. That's the way I store my
:> video camera batteries, since I use them very occasionally.
:>
:> Even if you take the best care of them, they won't last indefinitely.
:> I figure if you get 3+ years out of one, you are doing well. Typical
:> usage I believe is maybe 2 years.
:>
:> I learned this stuff by checking out the newsgroup:
:>
:> sci.chem.electrochem.battery
:>
:> Do www.groups.google.com search on this newsgroup and li-on and
:> battery life, etc.
:>
:> Dan
:
:Why is it that people who claims to have knowledge about care for Li-Ion
:batteries also claim of keeping them alive for only 3 years, while
thers ignore this care and feeding and are getting 10 years and
:counting with ours?

Hey, I wouldn't know. In fact I've never lost a li-ion battery. I've
simply read posts trying to find out the score. I've certainly had my
problems with Ni-Cad batteries, so I figure it's certainly worth the
trouble to read posts from people who seem to know what they are talking
about and learn from them.

Why don't you answer your question for me. I certainly can't. You
evidently have some ideas.

Dan

>
> Why is it that people who claims to have knowledge about care for Li-Ion
> batteries also claim of keeping them alive for only 3 years, while
> others ignore this care and feeding and are getting 10 years and
> counting with ours?

Probably because applications are different. Li-ion batteries lose very
little active material, however their effective DC-impedance increases a
lot with aging, typically 70% in 100 cycles.

Therefore:
1) For low rate applications (C/5 rate and below) Li-ion can live very long,
as such applications don't care about impedance
2) For high rate applications (above C/5 rate) I*R drop is going to kill
useable energy, therefore impedance increase cuts useable run-time
dramatically.

Battery is not going to "die" (like have no voltage on it or leak), but
it will be just useless for high-rate applications, device will die
right after turn-on.

You keep talking about 10 years. Let's get a little meat here,
so we talk numbers and not just heating air:
- what rate of discharge (in C-rate) you have in your device?
- how much run-time (in %) you get in your device as compared
with new-battery run time?

Regards,
Yevgen

Evgenij Barsukov wrote:

> >
> > Why is it that people who claims to have knowledge about care for Li-Ion
> > batteries also claim of keeping them alive for only 3 years, while
> > others ignore this care and feeding and are getting 10 years and
> > counting with ours?
>


> Probably because applications are different.

Duh. Battery life depends probably more on load cycling than any other
single thing.

Li-ion batteries lose very
> little active material, however their effective DC-impedance increases a
> lot with aging, typically 70% in 100 cycles.

Hmm. I don't know what you are using, but my products have Li+ in them
and at well over 100 cycles they are still well above 95% rated
capacity. (That's from randomly removed and tested devices,
incidentally)

>
> Therefore:
> 1) For low rate applications (C/5 rate and below) Li-ion can live very long,
> as such applications don't care about impedance

Hmm again. Sure they do, but the degree of caring is different.


> 2) For high rate applications (above C/5 rate) I*R drop is going to kill
> useable energy, therefore impedance increase cuts useable run-time
> dramatically.

Pure BS. I have three separate applications where I use Li+ cells. In
one, the average current is about C under full load. I have tested
numerous units repetitively including charge cycles. After 200 cycles
they are still at greater than 95% original capacity.
I will agree that high load currents will limit the time a load may be
active especially at the end of the discharge curve, however; but not
by that much

I noted some comments earlier in this thread; A Li+ with a terminal
potential of 3V is at nominal discharge, and it is perfectly safe to
discharge them to this point provided you charge them again within,
say, 96 hours.

>
> Battery is not going to "die" (like have no voltage on it or leak), but
> it will be just useless for high-rate applications, device will die
> right after turn-on.

True of any battery that is low; NiCads had this issue, NiMH had this
issue.


>
> You keep talking about 10 years. Let's get a little meat here,
> so we talk numbers and not just heating air:
> - what rate of discharge (in C-rate) you have in your device?
> - how much run-time (in %) you get in your device as compared
> with new-battery run time?
>

More specifically, how much real energy is available.

Cheers

PeteS


> Regards,
> Yevgen