Should I completely discharge my laptop battery?

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I have a Satellite A660 laptop with a Lithium-Ion battery pack.  I've
read that you should completely discharge batteries every month so
that the charger can recalibrate on what is 0% versus 100%.  Does this
apply to Lithium-Ions?  This also means I turn off the safety feature
of hibernating when the charge dwindles to 8%.  Doesn't the disk heads
crash once the charge dies?

Re: Should I completely discharge my laptop battery?

Once upon a time on usenet wrote:
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Yes, especially to Li-Ion as they last so long that the control circuitry  
needs new info on the state of the cells from time to time.

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No. Newer laptops are clever enough to stop in a controlled manner as the  
battery pack is exhausted. This is another good reason to fully discharge  
your battery now and then - so the control circuitry knows at what voltage  
it's near-empty.

"Humans will have advanced a long, long, way when religious belief has a  
cozy little classification in the DSM."
David Melville (in r.a.s.f1)  

Re: Should I completely discharge my laptop battery?

Thank you, misfit.  I googled both before posting and after your response.  
I didn't run across anything about saving hard drive heads from crashing wh
en the battery runs out, but I did see that one could set Power Options' Ad
vanced settings to turn off the hard drive at a certainly charge level.

About completely discharging the battery, Windows 7 safety features are fru
strating my attempts to do so.  It's not enough to create a new power plan  
(say, "Exhaust battery") where the computer never goes to sleep.  There are
 other controls hidden in the advanced power settings for Low, Critical, an
d Reserve battery levels, and the last one seems to be the problem -- you c
an't specify "Do nothing" (at least not via the GUI).  According to http://, you have to  
issue the following command:


*Sigh*.  All I want to do is discharge the battery.  Thank goodness for Goo

Re: Should I completely discharge my laptop battery?

On Wednesday, December 31, 2014 2:06:27 PM UTC-5,
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Oops, my bad.  The setting doesn't turn off the HD at a certainly
charge level.  It turns of the HD after a certain time.

Re: Should I completely discharge my laptop battery?

On Wednesday, December 31, 2014 2:06:27 PM UTC-5, wrote:
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On Wednesday, December 31, 2014 2:54:24 PM UTC-5,
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Darn, another error on my part.  It isn't the Reserve battery level
for which I had to use the powercfg command to set to do nothing.
It was the Critical battery level.

From googling yesterday (sorry, I didn't capture where I surfed), the
Reserved level is something different.  Windows & apps will save stuff
when Reserved level is reached.  From what I could find, reaching the
Reserve level doesn't trigger anything that interferes with the
discharging, e.g., sleep, hibernate.

Re: Should I completely discharge my laptop battery?

Once upon a time on usenet wrote:
Quoted text here. Click to load it

Just another word or two here; You actually don't want to *completely*  
discharge the battery pack - more like discharge it to the point where there  
is no usable power left in it. (There needs to be some power left to run the  
battery's internal monitoring electronics - if these die then the pack's a  

So just 'excercising' the battery by discharging to <5%, fully charging and  
repeating the process (maybe twice) should do it.

Mike makes some good points. Doing this can brick your half-good battery  
pack so deep discharging is usually something I only do when the pack has  
already got to the stage where it's only borderline useful, in the hope of  
regaining some 'capacity'.

Then again I use ThinkPads which allow me to set charging thresholds (I set  
my machine to start charging below 50% and stop at 85% and maybe twice a  
year perform a battery reset through ThinkVantage Power manager). Also I  
store currently unused packs in the fridge at ~40% charge.

Best of luck - and happy new year.

"Humans will have advanced a long, long, way when religious belief has a  
cozy little classification in the DSM."
David Melville (in r.a.s.f1)  

Re: Should I completely discharge my laptop battery?

On 12/30/2014 4:35 PM, ~misfit~ wrote:
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I have a contrary opinion.
I don't have any NEW systems, so this is slightly out of date,
but the concepts haven't changed.
Surely someone will come up with a counterexample that proves me stupid,
so, you'll have to decide whether you believe me.

I've only done this on a dozen or so batteries, so can't guarantee all are
that way.  All this assumes that a worn battery is just worn and does
not have shorted cell and not part of a stupid system design
that puts some of the cells right adjacent to the processor heat sink
and cooks them.

There are at least three levels of protection.
A coulomb counter basically counts the electrons as they go in/out.
Knowing the battery capacity, you can calculate the state of charge.  I  
believe the laptop polls the battery to determine
the state of charge and decides what to do.  That's an orderly shutdown
or hibernation as you've instructed in the setup.  There's likely a
voltage threshold too.

Battery and laptop vendors are very concerned that you don't sue them
over battery issues aka fires.  They care not that you have to buy
a new battery.  At retail, they probably make more profit off the
battery than they did on the laptop.  I read it on the internet so it
must be true.

There are at least two other discharge protections in the battery pack.
There's a shutdown voltage below which the control FETs open up and  
the battery.  This is NOT a controlled shutdown.  The battery just  
disconnects.  This is likely what you get when you turn off the protection
and run it till it quits.

There's a end of life voltage below which the pack will not recover.
You can't normally (see below) get there by discharging.
But you can get there
by sticking a discharged battery in the drawer for a couple of years letting
the discharge protection circuit systematically discharge the cell.
Sometimes it's firmware in the microcontroller that cannot be
reset unless you know the secret method and can reprogram it.
I've seen some that have a thermal fuse adjacent to a resistor.
At the end of life
threshold, they light up the resistor and blow the thermal fuse.
In either case, that battery pack ain't coming back.  The only pack
I've ever recovered had a PIC processor as controller and hitting
the reset did actually reset it.

Some of the old dell dimension packs would let you open them up,
charge the cells directly and they would run the computer again.
They'd continuously flash an error code and the battery gauge didn't
work, but you could run the computer.

I think it was a Toshiba that had an end of life mode that would
let you run the laptop off the battery.  OR, you could charge the
battery with the computer off.  If you wanted to run the laptop
off AC, you had to physically remove the battery.  Strong motivation
to buy a new battery, or in my case, strong motivation to never buy
another Toshiba.

I don't think I ever got a Thinkpad battery back.

So, why do batteries fail?
Over time, the cells just can't store as many electrons and capacity
decreases some.
But my experience is that the primary failure is due to increased
internal series resistance.
The symptom is as follows...
You charge the pack and the battery level shows 100%.
You disable the battery warning modes.
You run the computer and the meter drops steadily like
you'd expect until it hits some level like 40% and drops
immediately to zero and the computer shuts down soon thereafter.

If you take the battery out and test it under controlled conditions,
you find that most of the electrons are in there and can be recovered
at low current.  If you load with high current, the current x high  
series resistance
subtracts from the voltage to the point that the protection circuit
shuts you down at shutdown voltage.  The electrons are in there, but
the pack won't let you take them out.

Now, we get to the relevant part.
I've had a two systems that had about 50% usable battery capacity.
I decided I'd discharge them in hope of resetting the battery gauge.
I turned it on and let it sit till it quit.  And it never came back.

Here's my thesis.  I think the system sat there at low power with the
display backlight and hard drive off until it hit the point where the
laptop decided to take some action. Most of the capacity was gone.
When the disk started and the backlight started, the additional voltage
drop due to the increased current in the high battery internal series  
dropped the battery voltage all the way to the end of life threshold.
Game over.

That's why I'm very wary of running systems 'till they quit.  Seems to
work fine on slightly used batteries.  When the resistance gets high,
you may just kill a perfectly half-good battery.

If it ain't broke, don't fix it.


Re: Should I completely discharge my laptop battery?

Once upon a time on usenet mike wrote:

[snip very useful if slightly disjointed info]

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I have - the one in this 15" UXGA IPS 4:3 screen T60 - It's labeled 'Lazarus  
Battery'. I got it in a second-hand machine that used factory presets for  
charging (whenever charge drops below 95% top up to 100% - a usage pattern  
designed to get you to buy a new battery every two years or so).

When I got it it reported only 10% of new capacity so I did a 'battery  
reset' using ThinkVantage Power Manager (TVPM). It died, it wouldn't take a  
charge, the battery LED in the ThinkPad just flashed yellow. When powered up  
(with adapter) power manager said 'battery dead - replace'.

I threw it in a drawer for 6 months. Then I thought it's either rubbish or  
it's not so put it in a zip-lock bag in the freezer for a week, then put it  
in a ThinkPad, plugged in the adapter but didn't turn the machine on  
(concerns about condensation as well as not wanting TVPM to make a hasty  
decision and 'mark it' dead again). The battery LED flashed yellow for 15  
minutes - then stayed on solid yellow (meaning charging at 5% capacity or  
above)! I left it for a day or two (the LED had been on solid green for  
quite a while) then started the laptop. It now said the pack held 25% of  
original capacity (yay!).

That was two years ago and I've been using it since then in this machine  
that is never taken out of it's dock, using it as a UPS, set to charge when  
below 50% and stop at 85%. However I've since used TVPMs battery reset  
feature a couple of times, about once a year, and the reported capacity has  
risen to 40% of original. I have the laptop set to maximum power (as it's  
essentially used as a low-power draw desktop) and when there's a power  
outage it usually runs for at least 30 minutes before I decide to turn off.

That's a heck of a lot better than a 10% battery only good for 5 minutes  
then dirty shut down - or a brick.

I have two new repack batteries (a 6 cell and a 9 cell) stored at 40% charge  
in the fridge as I also have a 14" SXGA+ T60 that is used infrequently as a  
portable machine (I'm an invalid and don't get out much). The 14" has a 90%  
good battery in it ready to go - which reminds me, I must cycle that  

Happy new year.

"Humans will have advanced a long, long, way when religious belief has a  
cozy little classification in the DSM."
David Melville (in r.a.s.f1)  

Re: Should I completely discharge my laptop battery?

Mike, Misfit,

That was an overwhelming amount of insight into how batteries degrade.
I'm not really an electronic technology (anymore), but I appreciate
your sharing.  I don't anticipate going the lengths of
resuscitating a battery, though I'm sure that the information will
give the more technologically oriented readers some good ideas.

About Misfit's advice that one doesn't need to discharge much below
5%, this seems to imply (to me) that the charging circuitry isn't
losing track of what constitutes a low charge, it is losing track of
what constitutes a full charge.  Is this correct?

And this risk of bricking the battery -- from reading your responses,
it seems that this is a very plausible risk even if I just run it to
the point where the computer shuts down (not putting it in a drawer
for half a year).  It's a bit ambiguous, because one can interpret
this as the point at which there is "no usable power left", but then
again, there was that story about high internal resistance developing
a high voltage drop once the laptop draws current to do shutdown
activities.  As I said, I've got the laptop set to do nothing when it
reaches the Reserve battery level, but I have zero trust that windows
actually does nothing in the same way as it does if you were to just
yank the battery.

Anyway, given this ambiguity, it looks like 5% is what you recommend
as a good level to discharge to if I just want to recalibrate.

Re: Should I completely discharge my laptop battery?

Once upon a time on usenet wrote:
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Sort of. As Mike pointed out older cells can develop high internal series  
resistance (ISR). So it all depends on what your particular battery pack  
uses to trigger various states. Most use voltage and, if the ISR has risen,  
at lower voltages the cells still have the energy stored but can't deliver  
it at high load levels. So, with warnings turned off, when the computer asks  
for quite a few amps (CPU usage goes up) it can die suddenly. The power is  
still in the battery but it can only deliver it at low rates of current.

It's complicated stuff really and isn't helped by, as Mike says, laptop  
manufacturers err on the side of caution so will often have their control  
circuitry (in both battery pack and laptop) tell you a battery has less  
capacity than it does - and so limit your access to lower voltage states as  
the cycle count goes up. They make a lot of money out of selling replacement  
batteries. This doesn't take into account however what conditions the  
battery has been used under and whether it has been deep-cycled or  
constantly topped off.

(The latter is the default for most laptops and is really bad for  
batteries - especilly at raised temps, which a lot of batteries run at - and  
increases their ISR more quickly than if the batteries were cooler and were  
kept closer to the ideal state of charge for longevity - around 40% charge.)

My experience is with ThinkPads and the newer ones (post 2006 / T43 and  
later) allow the user to manually set the charge parameters. If you do that  
as I do - so the thing doesn't constantly charge to full every time the  
charge drops below 95% - then the batteries last twice as long at least.  
They also have software for 'battery reset' - where they fully charge /  
discharge the pack and recalibrate the control circuit built into the pack -  
basically what you're trying to do now.

So, not knowing how your system manages it's battery pack I can only give  
generalised advice. Almost all laptop battery packs use solder-tab 18650  
cells. I wish I could design and build a pack for my laptops that uses  
replaceable 18650s (like my flashlight does) and contained circuitry to  
manage them. Much like replacing AA cells in a remote controller. However as  
Mike pointed out the manufacturers make big money selling replacement  
batteries. :-/

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Are you not running the OEMs battery mangement software?

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Yeah, it might not reclaim a huge amount of charge 'marked bad' but it also  
shouldn't brick your battery pack.

"Humans will have advanced a long, long, way when religious belief has a  
cozy little classification in the DSM."
David Melville (in r.a.s.f1)  

Re: Should I completely discharge my laptop battery?

On Thursday, January 1, 2015 8:16:30 PM UTC-5, ~misfit~ wrote:
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It's a Toshiba Satellite A660, and the 64-bit Windows 7 OS is the one
from the OEM install discs.  The battery is also Toshiba, for this
laptop (perhaps for others as well, I never really looked into that).
Li-ion Battery Packmodel PA3817U-1BRS.  An OEM webpage I found is .
There just doesn't seem to be a way to set the upper percentage level
at which the charger stops charging, and the lower percentage level at
which it starts charging.  It charges to 100%, and as it discharges,
it encounters the Windows thresholds (Low, Critical, and Reserve) and
responds with the notifications and/or actions which have been
assigned to those events, e.g., sleep, hibernate.

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Thanks.  5% is good enough for me.  I'm interested in the gross
practices that can achieve gross improvements to longevity.  Thanks!

Re: Should I completely discharge my laptop battery?

On 1/1/2015 6:11 PM, wrote:
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There are several sides to this coin.

As a user, you get the best life out of your battery if you  learn
what it can do and manage YOUR activities to maximize that.
Maximum charge level is hard to work around because it's automagic.
Having a programmable setpoint is about the only viable alternative.
But when you use it, what are you gonna do?
You've decided that you want to stop at 25%.  Doesn't matter whether it's
manual or automagic.  If you're in the middle of something, do you shut  
down? Or do you finish your task?  For most of us, having a battery that
needs replacement less frequently is small consolation when you couldn't
finish the presentation and lost the order.
So, you charge as frequently as you can and use it as little as possible.
If it doesn't do what you want you bought the wrong laptop, or need a
second battery.

 From the vendor's perspective, as head of sales, do you want the ad
to say, 8-hr battery life?  Or 5-hr battery life and saves 20% on battery
replacement costs, cuz all our other laptops abuse the battery?
Or maybe you say 2X faster processor and hide the fact that it hardly
runs long enough to boot.
These marketing guys are pretty smart.  They know what sells.
The tablet-inspired expectation of 11 hour battery life is
affecting the whole laptop ecosystem.  May not be long until
virtually every laptop follows the "surface" model of tablet
with keyboard.  Most of us have wireless everything and don't
really need external ports.

Other factors include safety and protecting the replacement battery revenue
stream.  Nobody with the frugal gene would ever buy a new battery at
retail.  You can get crap batteries on ebay for cheap.  Sad news
is that if you buy a "OEM" battery, you may get a crap battery
anyway.  The plot thickens because the NEW battery
has been sitting in a container in
Arizona since the turn of the century.

Vendors can't have any of that!
I've seen laptops that refuse to boot with a counterfeit battery installed.
Some will run but won't charge. (you see that same symptom with some
counterfeit power bricks)
Others, give you a warning that you have to dismiss.
Some run the computer, but the battery gauge doesn't work and any
test reports "battery not installed."
The vendors want you to buy new laptops frequently.  And batteries
are priced/specified to encourage that.  Everybody wins...unless
you're concerned that, one day, the entire surface of the planet
might be covered in busted laptops.

The technology is quickly evolving.  Batteries, some, but management
technology has come a long way.  Vendors find it more marketable
to manage the best they can and replace the battery at your expense
There are a number of battery management technologies, but the trend
is to make is impossible for a mere mortal to fix one.

Back in the day, I'd match NiCd's and re-cell.  Turn 3 bad ones into
one good one.  You can't solder battery packs together.
Even if you're crazy enough to try to solder on them,
there's so little clearance that the blob won't fit the case.
If you get the tabbed ones and solder the tabs, there's often
insufficient room to fit the tabs in.
I have two generations of DIY tab welders and a real
CD spot welder.  Most of that is useless today.  You can change the
cells, but if the chip won't let you use it, you're done.
If you crack the case on a Lithium battery, you can sometimes charge
each cell individually to balance it and it may run the laptop, subject
to all the issues stated above.  I buy laptops with busted screens.
The battery is worth more than the value of trying to find a screen.
Working laptops at garage sales always have bad batteries.  That's
why they are for sale.  Ones with busted screens sometimes have
usable batteries.  It's worth a buck to find out.

So, who cares about any of this?
Cheap bastards like me!
Statistically, the percentage is near zero.
IF you use your computer to make money, the cost of a
replacement battery is noise level.

My life revolves around frugality and prospecting for deals.
I buy a lot of stuff at great prices.
I try not to think about the fact that I could have bought
one new computer for less than the prospecting costs of the
dozen crap laptop treasures I have hanging around.
That's why I call it a hobby.
THEY call it hoarding.  What do they know?  I can stop any time
I want... ;-)

There's a set of freeware diagnostic tools called PCWizard.
Last I checked, the sweet spot was the 2010 version, but it's
worth a try at the newer versions.
There's a battery tab that shows you what the pack thinks it
is, design capacity, current capacity, current state of charge,
voltage etc.
Whether it works for you is a crap shoot depending on whether it supports
the methods/protocols used by your laptop.  Do a reality check on
the numbers presented by battery analysis software.  Because of the
different protocols in the wild, sometimes the numbers are just WRONG.

Don't fix it if it ain't broke.

Re: Should I completely discharge my laptop battery?

Mike, your last post was entertaining.  As I said, though, I'm not as passi
onate about it as to make it a hobby.  I'm OK with the gross guidelines of  
discharging to 5% once a month.  I appreciate the rationale behind those gu
idelines as much as I appreciate the guidelines (which are not trustworthy  
without rationale).  Most of the time, I'm on AC, and the battery is only a
 UPS.  If it goes, I'll buy another (accepting the risk that it might have  
been on the shelf since the turn of the century).  I'll just complain to th
e vendor if it's crappy, and if they play hardball, I'll complain in public
.  I know it will not make it above noise level because so many people do t
hat anyway, but I am riding the technology improvement trend that is driven
 by capitalism.  Batteries today are heads and shoulders better than a deca
des ago...except to enthusiasts who intend to crack them open to extend the
ir lives.  More power to you if you do, though.

Re: Should I completely discharge my laptop battery?

On 1/2/2015 9:34 AM, wrote:
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Consensus seems to be that you should take the battery out if using it  
on AC.
Assuming the design of the charger stops charging when it gets to max,  
there's still the issue of heat.
I use mine little, so just leave the battery in on AC all the time.
If I used it a lot, I'd take out the battery.
I had more than one laptop where the battery sits two plastic
thicknesses away from the processor heat sink.
When you take the case off the battery, the ones closest to the
heat are discolored...and much higher resistance than the others.
Some designer oughtabeshot.

It's been said that lithium cells degrade almost as fast on the shelf
as if you use 'em sensibly.  A spare battery is great if you need to use
it.  If it's sittin on the shelf justincase, it may not be a good  
investment.  Still might be better sittin' in your fridge than
having it sittin' in that container
in Arizona till you buy it. ;-)

Re: Should I completely discharge my laptop battery?

On Friday, January 2, 2015 1:47:25 PM UTC-5, mike wrote:
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Understood, Mike.  However, my usage for the battery is 95% as a UPS,
and 5% as a power source when away from AC.  That's not necessarily
the proportion in which I value the two functions, but it is how the
battery spends its time (give or take a healthy margin of
uncertainty).  I guess I could get a real UPS for slight more than a

( product link shortened)

However, I need a battery anyway, so by keeping the battery in and
shortening the life by some amount, I get the convenience of a zero
footprint UPS and avoid having to buy a real UPS.  Subjectively, it's
worth it to me at this point, just based on the fact that I haven't
spent the time thinking about a UPS til now.  Within that scenario,
though, I still should try to maximize the battery life, which I did
by identify the gross best practice of discharing to 5% once a month.

Re: Should I completely discharge my laptop battery?

Once upon a time on usenet wrote:
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Andy - I don't know where you got this once a month figure from? IMO two or  
three times a year is the most you'd need to do this considering your usage  


"Humans will have advanced a long, long, way when religious belief has a  
cozy little classification in the DSM."
David Melville (in r.a.s.f1)  

Re: Should I completely discharge my laptop battery?

On Saturday, January 3, 2015 6:28:44 PM UTC-5, ~misfit~ wrote:
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I saw it a number of times during my web wanderings.  However, I just did another wander, and it seems that your advice above is more common.  Thanks.

Re: Should I completely discharge my laptop battery?

Once upon a time on usenet wrote:
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You're welcome. Once a month is simply wasting cycles IMO - there is a  
finite number in each cell (the number of cycles depends on variables but is  
still finite). This site is invaluable IMO;
especially this page

I've just finished cracking open a Sony Viao battery pack for the cells to  
use in a flashlight or other project. The (circa 2009) laptop was bought to  
me to fix but was deemed to expansive to repair by its owner so left with  
me. I salvaged various parts but for me the most valuable was the battery.  
Sony make good quality cells and the owner said the battery was still good.

The pack had a very complicated control PCB - around 50 SMDs on it with one  
IC having 48 legs, another with 30 legs, one with 20 leg and five ICs with  
eight legs. However it treated the six cells in pairs so only ran three  
'channels'. My Bosch 18v Li-Ion cordless power tools battery packs have five  
channels, one for each cell. The tools all use the same battery pack so I  
have two in use and two stored in sealed zip-lock bags in the fridge - which  
reminds me - I should bring those up to room temp and cycle them soon before  
chilling them again.

Anyway now I have another six 1st tier 18650 cells to play with. Learning  
their (remaining) capacity is the hardest part for me. If I wasn't so broke  
I'd buy a charger / analyser like the Maha Wizard One device that I bought  
ages ago for managing my Eneloops (I have a strong dislike of primary  
cells). However as it is I'm stuck with a 'dumb' charger that just charges  
until voltage is ~4.2v. Then I to do a timed discharge in a flashlight. :-/  
Very crude.

"Humans will have advanced a long, long, way when religious belief has a  
cozy little classification in the DSM."
David Melville (in r.a.s.f1)  

Re: Should I completely discharge my laptop battery?

On 1/6/2015 5:47 PM, ~misfit~ wrote:

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But effective.

I built a setup with programmable power supply and programmable load.
Makes nice graphs,but not clear that they have any value beyond curiosity.

I do have a suggestion.
use a variable power supply and a diode.
set the power supply so the output of the diode is at the low
limit discharge voltage. Set the current limit sufficiently high
to run the discharge load.
Now, when the phone rings and you forget, you won't overdischarge
your 18650s.
If you use a transistor B-E junction as that diode, you can
use the collector to drive a circuit that stops a clock when
low-end voltage is reached, or starts a clock you can use to subtract
from the total time to get the discharge time and you don't have to sit  
and watch it.

Re: Should I completely discharge my laptop battery?

Once upon a time on usenet mike wrote:
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I like to know cell capacity as I have some applications wher they run in  

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That first thing sounds good but I'm a little challenged when it come to  
electronics. I know basics (enough to make audio crossovers etc.) and have  
some components around the place.

Would you be so kind as to explain in a bit more detail? I'd be obliged.


"Humans will have advanced a long, long, way when religious belief has a  
cozy little classification in the DSM."
David Melville (in r.a.s.f1)  

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