Archived from groups: comp.sys.laptops (More info?)

My HP Pavilion 5375 is three years old, and the battery seems to be growing
weak. Now has about half-life.

I use this laptop primarily as a desktop -- using the batter no more than
five percent of the time, maybe once or twice a month, for an hour or two.
But I keep the battery in place, on charge, all the time.

My question is: When I get a new battery, should I just keep it out except
when I plan to use it?

Archived from groups: comp.sys.laptops (More info?)

"Ray" <rayj.balt@verizonDELETHIS.net> wrote in message
news:YJSfe.5909$941.1165@trnddc08...
> My HP Pavilion 5375 is three years old, and the battery seems to be
growing
> weak. Now has about half-life.
>
> I use this laptop primarily as a desktop -- using the batter no more than
> five percent of the time, maybe once or twice a month, for an hour or two.
> But I keep the battery in place, on charge, all the time.
>
> My question is: When I get a new battery, should I just keep it out except
> when I plan to use it?
>

Assuming a Lithium-ion battery this would sound typical for the decay of the
battery. Part of the decay is time based - a battery looses a very
significant amount of its capacity over 3 years. Part of it is the used
that you make of it - I estimate around 50C from the info you gave. If your
battery has half its capacity, it is actually ahead of the game, on average,
it should have deteriorated more than that.

Lithium batteries cannot be overcharged, unless the charging circuit is very
faulty. This is just as well, because an overcharged battery erupts in a
large fireball. In spite of any advice that you may hear to the contrary,
the battery can be left in place.

If you want to get maximum life from the battery, then store it at 40%
charged in the fridge (*NOT* the freezer), and charge it before you want to
use it. This is generally far too much trouble.

Archived from groups: comp.sys.laptops (More info?)

Thanks -- very useful info. Yes, it is a Li-Ion battery.

"Ye Electrik Fanne Clubbe" <ian.shorrocks@baehisclothessystems.com> wrote in
message news:42805f0e$1_1@glkas0286.greenlnk.net...
>
> "Ray" <rayj.balt@verizonDELETHIS.net> wrote in message
> news:YJSfe.5909$941.1165@trnddc08...
>> My HP Pavilion 5375 is three years old, and the battery seems to be
> growing
>> weak. Now has about half-life.
>>
>> I use this laptop primarily as a desktop -- using the batter no more than
>> five percent of the time, maybe once or twice a month, for an hour or
>> two.
>> But I keep the battery in place, on charge, all the time.
>>
>> My question is: When I get a new battery, should I just keep it out
>> except
>> when I plan to use it?
>>
>
> Assuming a Lithium-ion battery this would sound typical for the decay of
> the
> battery. Part of the decay is time based - a battery looses a very
> significant amount of its capacity over 3 years. Part of it is the used
> that you make of it - I estimate around 50C from the info you gave. If
> your
> battery has half its capacity, it is actually ahead of the game, on
> average,
> it should have deteriorated more than that.
>
> Lithium batteries cannot be overcharged, unless the charging circuit is
> very
> faulty. This is just as well, because an overcharged battery erupts in a
> large fireball. In spite of any advice that you may hear to the contrary,
> the battery can be left in place.
>
> If you want to get maximum life from the battery, then store it at 40%
> charged in the fridge (*NOT* the freezer), and charge it before you want
> to
> use it. This is generally far too much trouble.
>
>

Archived from groups: comp.sys.laptops (More info?)

Re: "I use this laptop primarily as a desktop -- using the batter no
more than five percent of the time, maybe once or twice a month, for an
hour or two. But I keep the battery in place, on charge, all the time."

That is your problem.

Experience has consistently and repeatedly suggested that if you are
going to use your laptop as a desktop, typically run on AC, the battery
should be removed, and ideally the AC adapter should be plugged into a
UPS. This may seem dumb, but the lithium laptop battery usually will
cost over $200, while a 350VA APC UPS can be bought (on sale) for $10 to
$30.

Properly cared for, Lithium laptop batteries can last 10 years and still
give nearly full service; I have a bunch of Toshiba 2487's (a dozen or
so) from 1995 to 1997 that still run their laptops for more than 2
hours. But when left in a laptop, batteries are usually destroyed
within 9 to 24 months (your 3 years is actually longer than typical).
It's not clear if the culprit is overcharging or heat (which
overcharging can produce, but overcharging isn't the only source), and
it doesn't happen in all cases or with all models, but this is the rule
rather than the exception.


Ray wrote:

> My HP Pavilion 5375 is three years old, and the battery seems to be growing
> weak. Now has about half-life.
>
> I use this laptop primarily as a desktop -- using the batter no more than
> five percent of the time, maybe once or twice a month, for an hour or two.
> But I keep the battery in place, on charge, all the time.
>
> My question is: When I get a new battery, should I just keep it out except
> when I plan to use it?
>
>
>

Archived from groups: comp.sys.laptops (More info?)

I have to disagree with a lot of your post.

While in theory overcharging should not be possible, the overwhelming
volume of user experience suggests that leaving the battery in the
laptop will result in loss of life. We can't prove that it's
overcharging rather than heat, but annectodal evidence suggests
overcharging, not withstanding the internal microprocessor present in
most laptop batteries that is supposed to prevent this.

Lithium battery systems are the most chemically stable of all battery
systems, for both single use and rechargeable. Almost all of the
battery manufacturers say that they can last 10 years (I posted a bunch
of references with links several weeks ago in this newsgroup; Duracell
says "7 years or more", and they are about the most conservative). I
have box of about a dozen Toshiba PA-2487 batteries here from 1995, 1996
and 1997 that still run Satellite 400 series laptops for more than 2
hours each.

Leaving the battery in place when the laptop is primarily and
consistently run on AC is bad advice whose probable consequence will be
to "throw away" 50% to 80% of the life of a $200 battery.

About 2 years ago, in this newsgroup, there was an extensive discussion
of this that went on for thousands and thousands of posts, over about 6
months. The consensus not of theoretical recommendations and what
"should" happen but of actual user experience was absolutely
overwhelming. Take the battery out and use it only when actually
traveling, it can last the better part of a decade. Leave it in the
laptop all the time, it will be gone in, typically, 9 to 24 months.
Even the people who ended up arguing that it was ok to leave it in, in
the end, ended up being mostly convinced that real world consequence of
doing so was early destruction of the battery.



Ye Electrik Fanne Clubbe wrote:


>
> Assuming a Lithium-ion battery this would sound typical for the decay of the
> battery. Part of the decay is time based - a battery looses a very
> significant amount of its capacity over 3 years. Part of it is the used
> that you make of it - I estimate around 50C from the info you gave. If your
> battery has half its capacity, it is actually ahead of the game, on average,
> it should have deteriorated more than that.
>
> Lithium batteries cannot be overcharged, unless the charging circuit is very
> faulty. This is just as well, because an overcharged battery erupts in a
> large fireball. In spite of any advice that you may hear to the contrary,
> the battery can be left in place.
>
> If you want to get maximum life from the battery, then store it at 40%
> charged in the fridge (*NOT* the freezer), and charge it before you want to
> use it. This is generally far too much trouble.
>
>

Archived from groups: comp.sys.laptops (More info?)

"Barry Watzman" <WatzmanNOSPAM@neo.rr.com> wrote in message
news:428297E6.3060700@neo.rr.com...
> I have to disagree with a lot of your post.
>
> While in theory overcharging should not be possible, the overwhelming
> volume of user experience suggests that leaving the battery in the
> laptop will result in loss of life. We can't prove that it's
> overcharging rather than heat, but annectodal evidence suggests
> overcharging, not withstanding the internal microprocessor present in
> most laptop batteries that is supposed to prevent this.
>
> Lithium battery systems are the most chemically stable of all battery
> systems, for both single use and rechargeable. Almost all of the
> battery manufacturers say that they can last 10 years (I posted a bunch
> of references with links several weeks ago in this newsgroup; Duracell
> says "7 years or more", and they are about the most conservative). I
> have box of about a dozen Toshiba PA-2487 batteries here from 1995, 1996
> and 1997 that still run Satellite 400 series laptops for more than 2
> hours each.
>
> Leaving the battery in place when the laptop is primarily and
> consistently run on AC is bad advice whose probable consequence will be
> to "throw away" 50% to 80% of the life of a $200 battery.
>
> About 2 years ago, in this newsgroup, there was an extensive discussion
> of this that went on for thousands and thousands of posts, over about 6
> months. The consensus not of theoretical recommendations and what
> "should" happen but of actual user experience was absolutely
> overwhelming. Take the battery out and use it only when actually
> traveling, it can last the better part of a decade. Leave it in the
> laptop all the time, it will be gone in, typically, 9 to 24 months.
> Even the people who ended up arguing that it was ok to leave it in, in
> the end, ended up being mostly convinced that real world consequence of
> doing so was early destruction of the battery.
>

Part of the issue is that the battery manufacturers won't issue any really
helpful advice on battery life and indeed are quite reticent on the issue.
However, the chemistry is mature enough for the life limiting factors to
have been well established. A lot of misinformation exists on battery life
and limitations. Many things affect the life of batteries and the absence
of any easily found hard and fast information fuels speculation and so
called anecdotal evidence.

When Nickel Metal-Hydride (Ni-MH) batteries first appeared, the marketing
men invented a problem with the traditional Nickel Cadmium (Ni-Cd) to
persuade people to buy the (at that time) more expensive Ni-MH. This
problem is the well known (and non-existent) 'Memory effect'. Ni-Cd
rechargeable technology, is one of the oldest rechargeable technologies
there is dating well into the 19th century. Memory effect was entirely
unknown until the marketing men invented it. You now read and hear about
this everywhere - the effect that people did notice was due to an entirely
different problem that afflicts under-used cells. I have revitalised many a
Ni-Cd battery with 'memory effect' by curing the other problem. The ironic
part is that the Ni-MH technology suffers from a problem that appears
similar to memory effect (but, again, is a different cause - 'voltage
depression').

Lithium Ion batteries are charged using a constant voltage regime for the
last 20% of the charge cycle. The charge terminates when the battery
voltage equals the charger voltage, and the charge current falls to zero (to
be accurate, a very small current equal to its own self discharge - which is
very low for Li-ion). The battery can be left in situ without overcharging.
Just as well as overcharged Li-ions explosively destruct. However, if the
Laptop is badly designed (and many are), the battery absorbs heat from other
circuits, and this will shorten its life considerably and is probably what
started the over charging story that has passed into folklore. Li-ions have
the narrowest temperature tolerance of any chemistry. Allowing the battery
to regularly reach 30 deg C in a laptop - not that unusual (even if
disconnected or otherwise properly looked after) will kill it in under 2
years.

It is true that if you are using the laptop on AC power for lengthy periods
with no intention of using battery power, then it makes sense to remove the
battery regardless.

Depending on how Li-ion batteries are used or abused, can severely affect
their life. I myself have examples here that are 12 years old and still
posses about 70% of the starting capacity. I also have examples that died
in less than a year. My laptop battery is 3 yers old and perfectly
serviceable (though not as much capacity as it used to).

Ian.

Archived from groups: comp.sys.laptops (More info?)

Re:

"When Nickel Metal-Hydride (Ni-MH) batteries first appeared, the
marketing men invented a problem with the traditional Nickel Cadmium
(Ni-Cd) to persuade people to buy the (at that time) more expensive Ni-MH."

Bullshit. We were discussing and bitching about the "memory problem"
with NiCads when there was NO alternative to NiCads .... e.g. before
NiMH batteries existed. The problems with NiCads, which are clearly and
by far the worst of any of the rechargeable batteries (also the oldest
of the rechargeable battery technologies) are very real. These problems
were not "invented" for any marketing purposes. From my Zenith Z-170
(aka Morrow Pivot) lunchbox in about 1985, to my Zenith Z-180 laptop in
about 1987, to my Dell NX20 in about 1992, the problems with NiCads were
being discussed and bitched at when there was no alternative technology.

Re: "The charge terminates when the battery voltage equals the charger
voltage, and the charge current falls to zero (to be accurate, a very
small current equal to its own self discharge - which is very low for
Li-ion). The battery can be left in situ without overcharging."

That may be the theory, but in practice, in laptops, it just does not
seem to really work that way.

Archived from groups: comp.sys.laptops (More info?)

Barry Watzman wrote:

> I have to disagree with a lot of your post.
>
> While in theory overcharging should not be possible, the overwhelming
> volume of user experience suggests that leaving the battery in the
> laptop will result in loss of life. We can't prove that it's
> overcharging rather than heat, but annectodal evidence suggests
> overcharging, not withstanding the internal microprocessor present in
> most laptop batteries that is supposed to prevent this.
>
> Lithium battery systems are the most chemically stable of all battery
> systems, for both single use and rechargeable. Almost all of the
> battery manufacturers say that they can last 10 years (I posted a bunch
> of references with links several weeks ago in this newsgroup; Duracell
> says "7 years or more", and they are about the most conservative). I
> have box of about a dozen Toshiba PA-2487 batteries here from 1995, 1996
> and 1997 that still run Satellite 400 series laptops for more than 2
> hours each.
>
> Leaving the battery in place when the laptop is primarily and
> consistently run on AC is bad advice whose probable consequence will be
> to "throw away" 50% to 80% of the life of a $200 battery.
>
> About 2 years ago, in this newsgroup, there was an extensive discussion
> of this that went on for thousands and thousands of posts, over about 6
> months. The consensus not of theoretical recommendations and what
> "should" happen but of actual user experience was absolutely
> overwhelming. Take the battery out and use it only when actually
> traveling, it can last the better part of a decade. Leave it in the
> laptop all the time, it will be gone in, typically, 9 to 24 months.
> Even the people who ended up arguing that it was ok to leave it in, in
> the end, ended up being mostly convinced that real world consequence of
> doing so was early destruction of the battery.
>
>
>
> Ye Electrik Fanne Clubbe wrote:
>
>
>>
>> Assuming a Lithium-ion battery this would sound typical for the decay of
>> the
>> battery. Part of the decay is time based - a battery looses a very
>> significant amount of its capacity over 3 years. Part of it is the used
>> that you make of it - I estimate around 50C from the info you gave. If
>> your battery has half its capacity, it is actually ahead of the game, on
>> average, it should have deteriorated more than that.
>>
>> Lithium batteries cannot be overcharged, unless the charging circuit is
>> very
>> faulty. This is just as well, because an overcharged battery erupts in a
>> large fireball. In spite of any advice that you may hear to the
>> contrary, the battery can be left in place.
>>
>> If you want to get maximum life from the battery, then store it at 40%
>> charged in the fridge (*NOT* the freezer), and charge it before you want
>> to
>> use it. This is generally far too much trouble.
>>
>>


hey, leave it in. that way they can sell more battaries. LOL

--rp

Archived from groups: comp.sys.laptops (More info?)

On Thu, 12 May 2005 09:09:20 +0100, "Ye Electrik Fanne Clubbe"
<ian.shorrocks@baehisclothessystems.com> wrote:

>Part of the issue is that the battery manufacturers won't issue any really
>helpful advice on battery life and indeed are quite reticent on the issue.
>However, the chemistry is mature enough for the life limiting factors to
>have been well established. A lot of misinformation exists on battery life
>and limitations. Many things affect the life of batteries and the absence
>of any easily found hard and fast information fuels speculation and so
>called anecdotal evidence.
>
(snip NiXX stuff)

>Lithium Ion batteries are charged using a constant voltage regime for the
>last 20% of the charge cycle.

Very incomplete and misleading.

They are charged with a current-limited constant voltage regime. The cutover
point is not 80% but is very much a function of the CC as a proportion of cell
capacity. At 0.55C we consistently had transition at 58% charge +/- 1%.

>The charge terminates when the battery
>voltage equals the charger voltage, and the charge current falls to zero (to
>be accurate, a very small current equal to its own self discharge - which is
>very low for Li-ion).

Not correct. Li-Ion cells held at CV will continue to accept significantly more
curent than their self-discharge figure. Sensible commercial chargers (speaking
from experience, using MAX1737) terminate charge after a fixed time from the
point where the current has dropped to something like 10% of the CC figure.
This is still substantially higher than the self-discharge current.

>The battery can be left in situ without overcharging.

Assuming a half-decent charger/regime. Unlike NiXX technologies (where some
maintenance - "Trickle" - charge is usually applied indefinitely), charging is
stopped completely, and does not recommence until the battery voltage falls
below some predetermined recharge threshold.

>Just as well as overcharged Li-ions explosively destruct. However, if the
>Laptop is badly designed (and many are), the battery absorbs heat from other
>circuits, and this will shorten its life considerably and is probably what
>started the over charging story that has passed into folklore. Li-ions have
>the narrowest temperature tolerance of any chemistry. Allowing the battery
>to regularly reach 30 deg C in a laptop - not that unusual (even if
>disconnected or otherwise properly looked after) will kill it in under 2
>years.

With modern laptops being thinner and packing more grunt into that thin package,
it is often difficult to control the temp at the battery bay despite the best of
intentions. Clearly if a laptop manufacturer has to compromise between any
demonstrable/benchmarkable characteristic and battery life, the latter will come
out a poor second. There go the good intentions. And they are all compromise
designs.

>It is true that if you are using the laptop on AC power for lengthy periods
>with no intention of using battery power, then it makes sense to remove the
>battery regardless.

Couldn't agree more.

>Depending on how Li-ion batteries are used or abused, can severely affect
>their life. I myself have examples here that are 12 years old and still
>posses about 70% of the starting capacity. I also have examples that died
>in less than a year. My laptop battery is 3 yers old and perfectly
>serviceable (though not as much capacity as it used to).

Same experience here.

Apart from use (work cycles) there are tow parameters that cause a decline in
the Li-Ion cell - resting state of charge and temperature. Life-shortening of
Li-Ion batteries increases with state of charge. Batteries left in the laptop
(at full charge, obviously) suffer most life-shortening as a result of the
combination of high SoC and battery bay temperature.

Archived from groups: comp.sys.laptops (More info?)

Again Lith Ion batteries can be lethal. I purposefully charged
a lithium button held in a clothespin. I charged it at 50 ma.
It blew like a firecracker after about 10 seconds. I then
got another one and put it on constant current charge and set it
at 5 ma. I did'nt blow but took the charge overnight without
any trouble. Thats what I meant about constant current charging
versus Voltage charging.
Kokomo Joe


**********************************************************
* Ham KH6JF AARS/MARS ABM6JF QCWA WW2 VET WD RADIO SYSTEM*
* Army MARS PRECEDED by AARS (Army Amateur Radio System) *
**********************************************************

Archived from groups: comp.sys.laptops (More info?)

"RedpIll" <RedpIll@takeIT.org> wrote in message
news:1187lbpr1uo6ca3@corp.supernews.com...
>
> hey, leave it in. that way they can sell more battaries. LOL
>

With the price of Li-ion batteries being what they are, I'm sure this
criterion is not low on the list.

Archived from groups: comp.sys.laptops (More info?)

On Thu, 12 May 2005 19:21:46 -1000, Joseph Fenn <jfenn@lava.net> wrote:

>Again Lith Ion batteries can be lethal. I purposefully charged
>a lithium button held in a clothespin. I charged it at 50 ma.
>It blew like a firecracker after about 10 seconds. I then
>got another one and put it on constant current charge and set it
>at 5 ma. I did'nt blow but took the charge overnight without
>any trouble. Thats what I meant about constant current charging
>versus Voltage charging.

All very interesting anecdote. But who said a lithium button cell was
lithium-ion?

Archived from groups: comp.sys.laptops (More info?)

"Barry Watzman" <WatzmanNOSPAM@neo.rr.com> wrote in message
news:42837783.5020607@neo.rr.com...
> Re:
>
> "When Nickel Metal-Hydride (Ni-MH) batteries first appeared, the
> marketing men invented a problem with the traditional Nickel Cadmium
> (Ni-Cd) to persuade people to buy the (at that time) more expensive
Ni-MH."
>
> Bullshit. We were discussing and bitching about the "memory problem"
> with NiCads when there was NO alternative to NiCads .... e.g. before
> NiMH batteries existed. The problems with NiCads, which are clearly and
> by far the worst of any of the rechargeable batteries (also the oldest
> of the rechargeable battery technologies) are very real. These problems
> were not "invented" for any marketing purposes. From my Zenith Z-170
> (aka Morrow Pivot) lunchbox in about 1985, to my Zenith Z-180 laptop in
> about 1987, to my Dell NX20 in about 1992, the problems with NiCads were
> being discussed and bitched at when there was no alternative technology.
>

The problem is that Nickel Cadmium batteries have always suffered from a
very real problem that manifests itself as the apparent inability of a cell
to accept and store a full charge. The memory effect problem was coined to
sell Ni-MH cells, but it is nothing to do with any memory. The nickel anode
of the battery 'grows' small whiskers which eventually cause a low
resistance path in the cell, shunting the charge current and providing an
alternative discharge path. The exact circumstances and reasons of this
growth are not fully understood (hence the differing opinions). Some cells
grow them in a short time, others take longer. The situation can be cured
by passing a large but short current pulse through the cell. A 40,000
microFarad capacitor charged to 40 volts is ideal for this, and provides an
instant but often short lived cure. The propensity to grow these whiskers
is not a function of how far the cell is discharged, but appears to be
dependant of the length of periods of inactivity.

As the Nickel Metal-Hydride cell uses a nickel anode. it too suffers from
this problem, but it does appear to be less prone. The Nickel-Iron wet
plate cell would probably suffer the problem, but the circulating
electrolyte when charging appears to dusrupt the growth.

Many years ago, we considered Nickel-Cadmium batteries as the starting
batteries for aircraft use, due to the weight advantage over Lead-Acid. The
above problem couple with a the more serious Negative Temperature Coeficient
precluded its use.

> Re: "The charge terminates when the battery voltage equals the charger
> voltage, and the charge current falls to zero (to be accurate, a very
> small current equal to its own self discharge - which is very low for
> Li-ion). The battery can be left in situ without overcharging."
>
> That may be the theory, but in practice, in laptops, it just does not
> seem to really work that way.

The official regime for charging a Lithium-ion battery disctates that the
battery be left floating. In practice there are many charge management
circuits that do terminate the charge. It should be noted that the majority
of charge indicators on laptops and other portable devices do not cease to
report charging when the charge terminates, but in fact indicate when the
constant current pert of the charge cycle terminates (at approx 80% charge).
The constant voltage part of the cycle will continue until the battery
voltage equals the charge voltage*, at which point, either the battery is
left floating, or the charge terminated.

One aspect of laptop design that causes battery life problems, is that in
order to cheapen the internnal design, some manufacturers use a tap on the
battery to power lower voltage circuits. This unbalances the discharge of
the individual cells, and poses considerable charge problems.

*In practice, a multi-cell battery has to much more closely monitored than
this. It has to be monitored at the cell level (or in practice groups of
paralleled cells).

Archived from groups: comp.sys.laptops (More info?)

"Ye Electrik Fanne Clubbe" <ian.shorrocks@baehisclothessystems.com> wrote in message news:42884fc5$1_1@glkas0286.greenlnk.net...
Date: Mon, 16 May 2005 08:53:59 +0100

The problem is that Nickel Cadmium batteries have always
suffered from a very real problem that manifests itself as the
apparent inability of a cell to accept and store a full charge.
The memory effect problem was coined to sell Ni-MH cells, but
it is nothing to do with any memory.

With 30 years of dealing with Ni-Cads, I've never seen much evidence
of this so called memory effect. As like all batteries that I know
of, will store less and less capacity as time moves on. And I still
have some 30 year old Ni-Cads that are still kicking. Although their
capacity is 1/10th or less of the original capacity.

The nickel anode of the battery 'grows' small whiskers which
eventually cause a low resistance path in the cell, shunting
the charge current and providing an alternative discharge path.

This only becomes a problem with discharged Ni-Cads. As Ni-Cads with
a charge will burn them off as soon as they are created.

The exact circumstances and reasons of this growth are not
fully understood (hence the differing opinions).

Hmm... I completely understand it. As it is a simple chemical
reaction. So what's so hard to understand?

Some cells grow them in a short time, others take longer. The
situation can be cured by passing a large but short current
pulse through the cell. A 40,000 microFarad capacitor charged
to 40 volts is ideal for this, and provides an instant but
often short lived cure.

We used to use a car battery and just quickly give it a shock of 12
volts just briefly. Sometimes one or two more times were necessary.
Although not all cells would always come back.

The propensity to grow these whiskers is not a function of how
far the cell is discharged, but appears to be dependant of the
length of periods of inactivity.

Actually it has nothing to do with inactivity. As the whiskers are
always in production during the life of the cell. The reason why you
don't notice it with a charged cell is because as soon as they get
created, they are blasted away from the charge in the cell. This
probably explains why Ni-Cads bleed off their charge faster than any
other battery type.

As the Nickel Metal-Hydride cell uses a nickel anode. it too
suffers from this problem, but it does appear to be less prone.
The Nickel-Iron wet plate cell would probably suffer the
problem, but the circulating electrolyte when charging appears
to dusrupt the growth.

Many years ago, we considered Nickel-Cadmium batteries as the
starting batteries for aircraft use, due to the weight
advantage over Lead-Acid. The above problem couple with a the
more serious Negative Temperature Coeficient precluded its use.

We often use Ni-Cads in our radio control aircraft. They actually
work quite well for us.

> Re: "The charge terminates when the battery voltage equals the charger
> voltage, and the charge current falls to zero (to be accurate, a very
> small current equal to its own self discharge - which is very low for
> Li-ion). The battery can be left in situ without overcharging."
>
> That may be the theory, but in practice, in laptops, it just does not
> seem to really work that way.

The official regime for charging a Lithium-ion battery
disctates that the battery be left floating. In practice there
are many charge management circuits that do terminate the
charge. It should be noted that the majority of charge
indicators on laptops and other portable devices do not cease
to report charging when the charge terminates, but in fact
indicate when the constant current pert of the charge cycle
terminates (at approx 80% charge). The constant voltage part
of the cycle will continue until the battery voltage equals the
charge voltage*, at which point, either the battery is left
floating, or the charge terminated.

All of my Li-Ion devices like cell phones, PDAs, etc. except for my
Toshiba laptops, will kick the charger back on after a period of
time if left on the AC. My Toshiba laptops will never kick the
charger back on unless you remove and insert the battery or the AC.

One aspect of laptop design that causes battery life problems,
is that in order to cheapen the internnal design, some
manufacturers use a tap on the battery to power lower voltage
circuits. This unbalances the discharge of the individual
cells, and poses considerable charge problems.

Supposedly for Ni-Cads, Ni-MH, and lead-acid batteries, trickle
charging will rebalance the cells once again even if wired in
series.

On the other hand, I've never heard of a laptop manufacture tapping
off a cell or two for some lower voltage use. How do you know of
this practice?

*In practice, a multi-cell battery has to much more closely
monitored than this. It has to be monitored at the cell level
(or in practice groups of paralleled cells).

For Ni-Cads and Ni-MH batteries, I believe they call it the delta
drop off. And how this is done is to electrically remove the charge
and monitor how quickly the voltage drops off. If it drops fairly
quickly, the fixed current charge is reapplied and checked later
once again.




Cheers!


__________________________________________________
Bill (using a Toshiba 2595XDVD under Windows 2000)
-- written and edited within WordStar 5.0

Archived from groups: comp.sys.laptops (More info?)

"BillW50" <BillW50@aol.kom> wrote in message
news:N%3ie.265$VB6.71@newssvr12.news.prodigy.com...

"Ye Electrik Fanne Clubbe" <ian.shorrocks@baehisclothessystems.com> wrote in
message news:42884fc5$1_1@glkas0286.greenlnk.net...
Date: Mon, 16 May 2005 08:53:59 +0100

The problem is that Nickel Cadmium batteries have always
suffered from a very real problem that manifests itself as the
apparent inability of a cell to accept and store a full charge.
The memory effect problem was coined to sell Ni-MH cells, but
it is nothing to do with any memory.

With 30 years of dealing with Ni-Cads, I've never seen much evidence
of this so called memory effect. As like all batteries that I know
of, will store less and less capacity as time moves on. And I still
have some 30 year old Ni-Cads that are still kicking. Although their
capacity is 1/10th or less of the original capacity.

The nickel anode of the battery 'grows' small whiskers which
eventually cause a low resistance path in the cell, shunting
the charge current and providing an alternative discharge path.

This only becomes a problem with discharged Ni-Cads. As Ni-Cads with
a charge will burn them off as soon as they are created.

EFC: The phenomenon has been noted in batteries that are charged but not
used. Then initial thin whisker is too high a resistance to be blown by the
1.2 volt cell voltage.

The exact circumstances and reasons of this growth are not
fully understood (hence the differing opinions).

Hmm... I completely understand it. As it is a simple chemical
reaction. So what's so hard to understand?

EFC: It is apparently not a chemical reaction. Thre phenomenon is well
documented in circumstances where no other reagents are present. Tin is
also known to exhibit the phenomenon and will hapily grow whiskers in an
inert atmosphere..

Some cells grow them in a short time, others take longer. The
situation can be cured by passing a large but short current
pulse through the cell. A 40,000 microFarad capacitor charged