Windows 7 - best protocol for carging a Laptop Battery

Asked By Rahul

19-Jun-08 10:02 AM

I just bought a new LiIon Laptop battery for my Dell Inspirion E1505 (dual
boot WinXP and Fedora).

I gave it my initial 10 hour charge. Now what? I started using it but
should I continue using it till the battery is drained and then recharge?
Or should I only drain it partially? If it is not drained fully how will
the Laptop learn (callibrate) itself to what the new capacity is?

Or is it recommended that I only partially discharge it? What's best for
the battery life?

Another point: How many times should I cycle it this way? In the long term
should I always wait for a full discharge; or can I charge it up from a
partially-discharged state or does it not matter?

I've gogled this but recieve conflicting advice.

--
Rahul

19-Jun-08 10:10 AM

As you likely will here too. Just use the computer according to the
instructions.

19-Jun-08 11:02 AM

From what I've read Li-ion batteries are immune to the 'memory' problems
of NiCd batteries - it does not really matter much when you charge them -
do what is convenient for you. You should also be aware that they loose
about 10% capacity per year and there is not a damned thing you can do
about it.

19-Jun-08 11:37 AM

I have a Dell and I've read and or been told that it has to do with
charge cycles, not amount charged like 20% or 99%.   If you get 1000
charge cycles and charge it everyday, you get about 2-3 years.

19-Jun-08 12:04 PM

run the laptop on the battery when you need to and when you do not
use the AC. If the battery runs down plug the laptop in and let the battery
charge.

19-Jun-08 03:47 PM

What was good for Nicad and NiMH is not good for Li-Ion. That first
discharge/charge cycle trains the charging circuits, it doesn't do anything
good for the battery.

Beyond that, keep it charged, don't run it to zero if you dont have to.
Don't let it get hot, that's a key factor. Li-Ions hate heat. I think there
was a discussion about this here a month or so ago...google "battery" in
this group.

I have good luck with laptop batteries by keeping them plugged in nearly all
the time, except when I need to roam. This laptop I'm typing on is 4+ years
old, and came with two batteries. They both work perfectly, at about 75% of
their original power.

-John O

19-Jun-08 10:49 PM

yes and no.  3 years is normal for lithium ion, but it's usually
regardless of whether the battery is used or not.  Some charging
issues (depends on platform) may dictate that it is safer to not
let it fully discharge... YMMV.  But a lithium ion sitting on
a shelf is in a state of decay as well.

20-Jun-08 02:54 AM

You will receive conflicting advice here and also on the internet if you
google these things.

There are only three things that you really need to know.

First: remove the battery from the laptop when you are running on AC and not
charging the battery.  The heat generated by the internal components of the
laptop warms the battery up.  Heat destroys Li-ion batteries.

Second: It is not necessary to discharge the battery before charging it.
Li-ion batteries do not suffer a memory effect or any other effect which
stops you from charging from partially discharged.  You may hear advice
about not completely discharging the battery, but I have found no evidence
to support this view (and I use these batteries in aerospace applications).
I have 3 examples of batteries that are nearly 15 years old that have often
been fully discharged.  Fully discharging periodically (say every six months
or so) will recalibrate the battery charge monitor circuit.

Third: Li-ion batteries do like to be used occasionally.  Don't leave one
standing idle for months on end.

20-Jun-08 02:55 AM

The evidence for this is largely anecdotal.  I have batteries that are
nearly 15 years old which, if this theory were true, would be useless.

20-Jun-08 02:59 AM

If you get 1000 charge/disharge cycles then you have got a very unusual
Li-ion battery indeed.  500 is generally the top end of the range.  Of
course this is full discharge.  If you only half discharge the battery, then
you will get 1000 half cycles, but it's only really 500 full cycles.

20-Jun-08 03:00 AM

Where did you get 3 years from?  Thes batteries are quite capable of lasting
10 years or more.

20-Jun-08 03:07 AM

Why?  I often hear this but when this advise is trotted out, the adviser
doesn't actually know the answer.  It's rubbish of course.


Why? Same as last answer.  There is no evidence that fully discharging a
battery does it any harm.  Overdischarging is dangerous, but the monitor
circuits won't let you get even close to this condition.


Correct.


Bad idea, unless you have one of the few laptops that doesn't have any heat
producing parts near the battery.

20-Jun-08 03:10 AM

And absolutely do not leave it in the car, especially on a hot day.
That can kill it in a few days.  I hear freezing is pretty bad too, but
that's not a danger here.

--
-eben   QebWenE01R@vTerYizUonI.nOetP   royalty.mine.nu:81

Unix is user-friendly; it's just picky
about who it makes friends with.

20-Jun-08 07:35 AM

Recharging them from zero often (usually) results in heating up. Maybe with
proper airflow and an open design a full discharge/recharge regimen isn't
any issue, but in a real-world portable device it definitely matters.
Smaller recharges equal less heat. Your advice about removing the pack when
on AC kinda plays into that. Plus a lot of charging systems are stupid.




I've been through a lot of laptops in the past 15 years, and my Li-Ion packs
always last a long time. And that's the way I treat them. <shrug>

-John O

20-Jun-08 10:59 AM

Really - I was not aware that rechargable Li-ion batteries had been around
that long! So are they really as good as new or only carrying 15% of
original charge? Did you do any measurements?

21-Jun-08 12:45 AM

...

Hmmm... you have a lithium ion battery that is 10 years old and
functioning normally?  Interesting.

23-Jun-08 03:26 AM

Li-ion batteries have ben around since the early part of the 1990's (and
probably before).  The examples cited all exhibit close to their original
capacity (as far as I can tell - they run for near enough the orignal time).
One of the batteries reports that it is only 70% charged after being fully
charged, but otherwise works as well as the others.

23-Jun-08 03:28 AM

No, I have 3 (three) lithium ion batteries that are *15* years old and still
functioning.

My camcorder battery is now 8 years old and working normally.

23-Jun-08 03:35 AM

Lithium-ion batteries have an efficiency of nearly 99% and as such generate
(as near as makes no difference) no heat of their own while charging.  This
is true as long as the charging is carried out correctly.  Removal of the
battery while running on AC has nothing to do with internal heat from the
battery (as many suggest), but heating of the battery by other parts of the
laptop (such as CPU, GPU, hard drive and so on).  Li-ion battery charging
systems are never stupid.  They have to be designed to fairly rigid and
close tolerance specifications.  Lithium-ion batteries can be extremely
dangerous if they are not charged and discharged properly, but if the
charger and protection circuits are properly designed, this won't be a
problem.

23-Jun-08 08:53 PM

Have the Li-ion batteries essentially replaced the NiCad ones?   Or are the
latter just cheaper (just guessing), and still used for economy, or for some
other reason?

24-Jun-08 03:30 AM

Nickel-Cadmium batteries are no longer recommended for new products.  This
is due to environmental concerns of the relatively toxic cadmium.  They are
available for support of older products that used them.  Although Nickel
Metal-Hydride appeared as a replacement, they are are not direct
replacements in most applications.

24-Jun-08 04:08 AM

Interesting - thanks.
But is this because they weren't available in the identical size packages,
with the same electrical capacity (i.e., voltage, ma-hrs, etc)?   Or because
of the external charging circuitry (if any) possibly having different
requirements?

24-Jun-08 08:15 AM

505
=20
ed
ew
est

t=20
ou
are
ned
are
ss.


and
=20
e
r
his
=20
l
es,=20
cause=20
See
http://www.google.com/search?hl=3Den&q=3Dnicad+vs+Nimh&btnG=3DGoogle+Sear=
ch
and
http://www.servocity.com/html/nicad_vs__nimh_batteries.html

24-Jun-08 05:02 PM

OK, thanks for the links.     There seems to be a set of advantages and
disadvantages for each type.

24-Jun-08 05:08 PM

A-yep, as it is with most things in life! ;-)


=20

it

=20
=20
e
it
=20

t=20
n
of
=20
al
g
are
or

ey
kel
arch

26-Jun-08 02:50 AM

Although the electrical characteristics are pretty similar (apart from the
greatly increased mAh capacity), Ni-MH has an exothermic charge reaction
(Ni-Cd was endothermic).  This means that when rapid charging the cells, it
is necessary to have temperature monitoring and cutout which was unnecesary
with Ni-Cd.  However, a temperature sensor could be used to detect the end
of charge condition for Ni-Cd (as the charge power had to be disipated as
heat once the battery stopped absorbing it's charge).  This cannot be so
easily done in Ni-MH as the cells get warm anyway.

26-Jun-08 03:28 AM

Interesting.   And what a pain...


I would have thought the end of charge condition (for any battery) could
have been sensed by a dropoff in the charging current when the battery is
nearly fully charged.
If, for example, one used a fixed charging voltage source, and charged the
battery through a resistor, the current would start off high, and then drop
as the battery got charged.   Apparently they don't do it that way.

26-Jun-08 04:29 AM

Both NiCd and NiMH cells are charged with a constant current.  A
slight drop in cell voltage, at least with NiMH, indicates full
charge.

--
Måns Rullgård
mans@mansr.com

26-Jun-08 01:47 PM

OK, with later retrospect, I was guessing that might be the way they
actually do it, since it's probably safer (since there is no huge initial
current inrush, like there would be for a dead battery).

But the problem with that method is that you can't tell when its fully
charged as easily as you could if you were to use the constant voltage
source method (and just monitor the charging current), from what I can see.

02-Jul-08 04:31 PM

OK, with later retrospect, I was guessing that might be the way they
actually do it, since it's perhaps a bit safer (since there is no large
initial
current inrush like there would be for a dead battery).    But....

But the problem with that method (constant current charging) is that you
can't tell when
the battery is fully charged as well as you could if you were to use the
constant voltage
source (with a series resistor) method, and monitor the charging current
(from I what I can see).

So I still don't see why they don't do it this way.

10-Jul-08 03:25 AM

Actually modern charge monitoring circuits have got quite sophisticated, and
are quite adept at detecting end of charge condition using the electrical
characteristics of the cells.  However, the best of them still use some form
of temperature monitoring as an extra clue.

10-Jul-08 03:31 AM

The two main differences that affect choice are:

Mi-MH: Has a greater capacity per unit volume (at least 4 times these days -
and rising).  Because they are lighter, an even greater energy capacity per
unit weight.

Ni-Cd: Can deliver very high discharge currents with practically no loss of
capacity.  They can even deliver what might be regarded as short circuit
currents with little damage.  Ni-MH suffer damage with even moderately high
currents (but even this is improving as we type).