Li Battery

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I got a replacement battery for my laptop.
It is a Li-Ion type.
6 cell 4400 mAh 10.8 volt

In the package docs it states that I should cycle the battery all the  
way down, recharge it and do this several times to improve its  
capability.

What is happening to the battery doing this?

If not done what can I expect in terms of the amount of loss of use?




Re: Li Battery
wrote:

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Nothing.  It's training the battery charging circuit to recognize the
particulars of that battery,
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Could be quite a bit because the charger may shut down before
completely charging the battery.

Re: Li Battery
Den torsdag den 12. november 2015 kl. 18.03.35 UTC+1 skrev OldGuy:
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afaik you shouldn't do that for Li-Ion, it was the old NiCd that needed that  

-Lasse

Re: Li Battery
On 11/12/2015 11:15 AM, Lasse Langwadt Christensen wrote:
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That's what I found out too. You shouldn't run a Li-Ion down completely.
The Li battery in my DSLR has been going strong for the last 8 years.
The camera says it's in good shape.


Re: Li Battery
wrote:

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They can be run down but there is a limit.  If it's never run down,
how do you know its capacity?  Laptop charging circuits have gas
gauges and need to run down the battery to calibrate.  

Re: Li Battery

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If the battery sits on the shelf, then that self discharge does not
show up on the gas guage. Plus the LI batteries I've used tend to
increase with capacity in the first few cycles.

Cheers

Re: Li Battery


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Everything I've read so far says never fully discharge lithium.

But I think the gas gauge could be the reason I've never had to buy cells  
for my DIY ecig.

All my cells come from recycling bins in various shops, I've gone on the  
assumption that one weak cell causes the whole battery pack to be scrapped -  
but so far, I've never found that one weak cell.

Presumably a chip in the battery pack informs the user that their battery is  
worn out, and they throw it in recycling - whether it is or not.  


Re: Li Battery
On Fri, 13 Nov 2015 20:23:18 -0000, "Ian Field"

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That depends on what you mean by "fully", I suppose.  Discharge to
zero?  No, that's not a good idea (but not as disastrous as SLACs).
However, laptops won't allow this anyway.  There isn't much energy
under 3.1V (from memory) so there is no point in discharging below
that point.
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I suppose that depends on what you define as a good cell, too.  I've
had batteries go bad.  I know they're bad because they discharge
significantly faster than a new cell.  

Re: Li Battery
On 11/13/2015 4:53 PM, krw wrote:
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Back in the day, I built an automated test fixture to evaluate laptop cells.
Ignoring the obvious exceptions of shorted cells and those that had
been obviously overheated, I found that virtually every cell from
a "bad" laptop battery pack would produce it's full rated number of
electrons if discharged at low current.

The failure mode is increased internal series resistance.  Battery
management chips deal with that in different ways, but the result
is pretty much the same...buy a new battery.

Do the math.  Using some round numbers, if your laptop takes 60W and
has a 10V battery, that's 6 amps AVERAGE.  The difference between full  
and empty
for a lithium cell is about a volt.  1/6 of an ohm series resistance per  
cell or cell pair renders your pack useless for powering a laptop.
And the peak current may be much higher than that.

At far less resistance, you see the symptom that the battery gauge
seems to be normal down to 50%, then instantly drops to zero, but the
laptop may run for a long time at that level, if it's not working too
hard...depending on how the
battery management system is programmed.  Even if it's a coulomb counter,
the voltage drop caused by the peak current demand can trip the voltage
level safety limit.

Re: Li Battery


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The ecig I use recovered cells on is just a little heating element - a small  
coil of resistance wire.

Commercial ones are from about 1.6 - 2.8 Ohms, the coils I rewind are  
somewhere around the 1 Ohm mark.

Maybe less than peak demand in a laptop - but not trivial either.  


Re: Li Battery
Charge/discharge efficiency is not 100%, nor is leakage perfectly matched in  
the set.

So, over time, some cells get lower than others.  Without any cause at all,  
as far as the controller knows -- no terminal current was even flowing.

By recharging a flat pack, the most-charged cells go up from, say, 40% to  
90%, while the least-charged cells go up from, say, 20% to 80%.  There's  
less charge in the already-charged ones, and more charge in the less-charged  
ones.

Same thing happens on discharge, it's a decay process internally.  Not  
perfectly divided, coulomb per coulomb, among cells.

So having <100% charge efficiency actually helps, because that loss  
manifests as current-sharing resistors in your pack of near-voltage-sources.  
And over numerous cycles, the charge per cell gradually gets back in  
balance.

Cool, huh?

So if you leave your <anything with multiple cells> sitting plugged in too  
long, unplug it and give it a few cycles every once in a while.  Like every  
month or so.  Discharge until a warning pops up, charge until it's finished.  
You can use smaller cycles, but then you have to watch it intently, which is  
silly.  Hopefully... the manufacturer decided to treat their cells well, and  
set generous thresholds for "shutdown warning" and "stop charging".  But  
even at the limits (4.25V charged and 3.2V discharged, or thereabouts),  
you'll recover way more life through balancing than you lose by leaving them  
totally out of whack.  Battery life is only until the lowest cell drops out,  
and charge time is only until the fullest finishes.

I had one laptop that I left plugged in for over a year (didn't need it, had  
another -- only reason I left it running was f@h), the cells nearer the  
warmer insides died more or less.  The charge circuit completely refused to  
use it anymore.  Later, I opened the pack, and the one bank of them was  
under 1V.  (The rest were okayish, over 2.5V.)

My current laptop no longer reads battery charge correctly (it thinks it's  
at 100%, until it flips shit and panicks to standby), but varies between 1-2  
hours actual run time, depending on how much I've left it sit around between  
uses.

Tim

--  
Seven Transistor Labs
Electrical Engineering Consultation
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Re: Li Battery


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Laptop battery packs have a thin strip PCB with various chips etc on it,  
AFAIK: they use shunt regulation as a halter for any cells getting close to  
critical terminal voltage.

This must have a voltage sensing divider, I'm sure they do everything  
possible to minimise sensing current - but there must be some.  


Re: Li Battery
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All I've seen are protection only: disconnect if the charge goes too high,  
or the discharge goes too low.  And logging (charge reading chip) and info  
(EEPROM with mfg/sn#/key/..).

They certainly aren't large enough to dissipate excess charging power per  
cell!

Tim

--  
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
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Re: Li Battery
On Thu, 12 Nov 2015 09:03:15 -0800

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I guess the battery is imitation, made in China, which explains how
they were able to add some instructions meant for NiCd batteries.

joe


Re: Li Battery
wrote:

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You obviously have no - or little - experience with LiXX cells and
their care and feeding.  What krw said first up is correct - it is
part of the device's capacity calibration process.  It is very common
advice with many appliances from reputable manufacturers.  RTFM.

Also, Martin's observation: "LI batteries I've used tend to increase
with capacity in the first few cycles." is what I have experienced in
our testing of virgin cells.  (I have designed a commercial LiXX
charger, which project involved significant testing/cycling).

Re: Li Battery
On Sun, 15 Nov 2015 10:35:31 +0800

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Good, I stand corrected, thanks.
What exactly is being 'calibrated'?

joe


Re: Li Battery
wrote:

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Capacity.

Re: Li Battery
wrote:

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The host device - in this case a laptop - provides both a readout of
"remaining battery capacity" as a percentage (of full capacity) and
provides low battery warnings and shutdown actions.  To know what the
capacity is, it needs to experience the limits and store the values.

At the end of full charge, it notes that as 100%. But where is 0% (of
USABLE capacity)?  That answer is found by full discharge, down to the
pre-ordained (in the host) cutoff voltage - which is hopefully above
the battery protection module's shutoff point.

Now it knows what the usable capacity is, and can quote numbers to the
user, and make operational decisions based on those numbers.  The only
remaining kink in the scheme of things is that the capacity will
increase over the first two or three cycles.  Hence the recommendation
that the battery be cycled fully a few times before use - as the user
is unlikely to do this in service and therefore pre-emptive warnings
and actions may be misplaced.

Re: Li Battery
wrote:

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You always have to differentiate between the capabilities and behavior
of the battery, and the behavior of it's protection circuitry.

When the battery protection circuitry is present, you're hostage to
the firmware present and you've really no alternative but to do what
the mfr tells you to do, right or wrong.

Sometimes the battery and it's control hardware/firmware are poorly
matched (as is the 'gauge' monitoring of Li Ion cells) resulting in
early death of the combination. This is not through fiery explosion,
just faulty capacity reporting or poorly managed and ineptly deployed
'End Of Discharge' or 'End Of Charge' events.

There's often a disconnect between the battery protection firmware and
that of the equipment in which it is used, even in dedicated
single-product applications.

You might get useful help from other users of the same equipment,
who've been deeling with it longer.

RL

RL

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