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'[ee] Li Battery experts?'
2005\06\22@034936 by Robert Rolf

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Hoping to drawn on the collective wisdom to be found here.

I have a 3x3 Li laptop battery pack that is dead.
Two of the 3 sets of paralleled cells (Panasonic CGR17670HC)
appear to be fine (3.56V under 100R load),
but the middle triplet was sitting at 0.35 volts.

I figured I could bring it up to nominal voltage (3.6)
by supplying it with a current limited 4.5 volts for
several hours.
However, it draws negligible current, (10 mA) and
after 96 hours it's reads 4.2 V, but drops to 1.5V if
loaded with 100R and completely drains to 0.1 V after
about 4 minutes. What is also odd is that 24 hours
into the charging the terminals would read 3V, but
2V under load, so the battery actually got worse with
longer charge.

What is likely to be wrong with this pack's chemistry
that it draws little current, even at 9V, yet
shows terminal voltage for many times longer than
a capacitor would?

I assume that these batteries are unrecoverable,
but would like to understand what happened so I can
be more successful with my next attempt.

Thanks in advance for any advice.

Robert

2005\06\22@041131 by p.cousens

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My current favourite is to wrap them in kitchen roll then put them in a
freezer bag.
Leave them in the freezer for at least four days.
Take them out leave them still wrapped for over 12 hours to warm up  
Then put them back in the unit they designed for and run them flat
before recharging them

 PC  

> {Original Message removed}

2005\06\22@042351 by Michael Rigby-Jones

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{Quote hidden}

Li-Ion cells are almost always unrecoverable if they have dropped much below about 1.5v IME.  I've had some success with ones that have gone down to ~2volts, but you have to charge at very low current until the voltage gets up to ~2.8volts or there is a danger of overheating as partial shorts can form inside the cell.

Regards

Mike

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2005\06\22@045001 by Howard Winter

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Robert,

On Wed, 22 Jun 2005 01:47:33 -0600, Robert Rolf wrote:

> Hoping to drawn on the collective wisdom to be found here.

Well I'm no expert but I have read some of the specs some time ago...  :-)

> I have a 3x3 Li laptop battery pack that is dead.
> Two of the 3 sets of paralleled cells (Panasonic CGR17670HC)
> appear to be fine (3.56V under 100R load),
> but the middle triplet was sitting at 0.35 volts.

I think you're saying that you have a 3x3 series/parallel matrix, so the output voltage of the whole battery
is three times a single cell voltage (about 10.2V or thereabouts).  It's usual to have three series strings
and have the paralelling at the ends - from what you are saying they are paralelled in threes, and each three
is then connected in series - is this right?  If so, that's unusual!  One failure mode of a cell is shorting
(or low resistance) between the plates, and with the wiring I think you are describing that would suggest one
of the middle three has this problem.

> I figured I could bring it up to nominal voltage (3.6)
> by supplying it with a current limited 4.5 volts for
> several hours.

No!!!  First it's really dangerous to go into a Li battery like this - they react really badly and can easily
explode if mistreated - and unless something has changed recently, 4.5V is too high a charging voltage - 4.1
or 4.2 is the norm, and you have to use the right one of these (subtle differences in construction cause the
difference, and different Panasonic cells need one or other of these).  Current limiting is not good enough
with Li - you need accurate voltage control.

> However, it draws negligible current, (10 mA) and
> after 96 hours it's reads 4.2 V, but drops to 1.5V if
> loaded with 100R and completely drains to 0.1 V after
> about 4 minutes. What is also odd is that 24 hours
> into the charging the terminals would read 3V, but
> 2V under load, so the battery actually got worse with
> longer charge.

Li batteries aren't just a collection of cells wired together - they will have at least some electronics to
protect the thing from abuse - most manufacturers won't sell individual cells without the protection circuit,
because of the danger.  Laptop batteries often have actual intelligence in the electronics, including keeping
the history of charge/discharge cycles, and looking after the charging.  You can't just bung any old voltage
in there and expect the electronics to let it happen - the electronics is probably stopping your attempted
charge voltage getting through to the cells.

> What is likely to be wrong with this pack's chemistry
> that it draws little current, even at 9V, yet
> shows terminal voltage for many times longer than
> a capacitor would?

If you put 9V across a Li cell and it didn't explode, the protection circuitry saved you!  The whole pack
should be about 10.2V as I said, so if that's where you put the 9V then it wouldn't have had any charging
effect.

> I assume that these batteries are unrecoverable,
> but would like to understand what happened so I can
> be more successful with my next attempt.

I think it's unrecoverable if when the correct voltage is applied to the whole battery, it doesn't hold a
charge.  The only recovery would be to dismantle it and replace the cells (or possibly try to recondition them
individually) but Li cells do have a limited lifespan, and I think yours has reached it.  Annoying, I know,
but when you've eaten the rabbit stew, it's too late to call the Vet!  :-)

Cheers,


Howard Winter
St.Albans, England


2005\06\22@082001 by olin piclist

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p.cousens wrote:
> My current favourite is to wrap them in kitchen roll then put them in a
> freezer bag.
> Leave them in the freezer for at least four days.
> Take them out leave them still wrapped for over 12 hours to warm up
> Then put them back in the unit they designed for and run them flat
> before recharging them

Didn't you leave out the part about the dead fish and the proper phase of
the moon?


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com

2005\06\22@091538 by Russell McMahon

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Mini tutorial in applied engineering thinking:

>> My current favourite is to ... Leave them in the freezer for at
>> least four days.
>> Take them out leave them still wrapped for over 12 hours to warm up
>> Then put them back in the unit they designed for and run them flat
>> before recharging them

> Didn't you leave out the part about the dead fish and the proper
> phase of
> the moon?

I used to remind my son of "standard warning number one" viz - Try to
avoid trying so hard to be funny that you risk missing something
important.

There is anecdotal evidence from other sources who claim to have had
firsthand success regenerating Li Ion batteries by this means. (Google
knows). Some suggest that this may reset internal protection circuitry
(for whatever reason) but this seems less likely to me.

Li-Ion electrolytes typically freeze at around -40C (or -40F if in the
US).
(NimH and NiCd freeze at about -60C!).

Most freezers will not freeze any of the above batteries so there is
unlikely to be damage from crystal formation. Other damage may, of
course, occur. Wrapping the cells will slow temperature changes and
MAY affect the end result. Effective folk cures of all sorts often
enough utilise mechanisms which are scientifically sound but little
understood by the protagonists. Rejecting the possibility of such
mechanisms existing, out of hand, may blind you to useful new
knowledge. And, in any given situation, may not. Unless one is utterly
expert at judging such situations a priori it can pay to err on the
side of careful open mindedness.

It may well be that in this case there is some form of chemical action
triggered by this cooling, or it may be that mechanical aspects do
have some effect.

Maybe not, but keeping dead fish out of the freezer, and one's brain,
in the meantime is probably wise.

It may have been wiser to ask Peter for a description of the efficacy
of his results to date and some quantitative or qualitative examples
rather than attempting to demean, essentially ad hominem.





           RM



2005\06\22@172004 by p.cousens

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Got a chd1000 mp3 hard disk player
Li batt after one year of constant use the batt died
Freezer one week and three months later still good.
lots of phones, mine and friends have also benefited from this advice
Try it your self, better to cook the fish and forget about the moon

 PC

> {Original Message removed}

2005\06\22@203715 by olin piclist

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Russell McMahon wrote:
> There is anecdotal evidence from other sources who claim to have had
> firsthand success regenerating Li Ion batteries by this means. (Google
> knows). Some suggest that this may reset internal protection circuitry
> (for whatever reason) but this seems less likely to me.
>
> ...
>
> Rejecting the possibility of such
> mechanisms existing, out of hand, may blind you to useful new
> knowledge. And, in any given situation, may not. Unless one is utterly
> expert at judging such situations a priori it can pay to err on the
> side of careful open mindedness.

Some old "wives tales" or "urban legends" actually do work, although almost
never due to the supposed mechanism.  Many are just bunk.  In general I
wouldn't offer one as advice without solid evidence.  Else how is it really
any better than the dead fish method that "everyone knows" works?

In this case however, I'd stay away.  Lithium batteries have the nasty habit
of catching fire and taking the nearby surroundings with them.  These are
not things to handle outside published specifications without taking some
serious precautions.

This would make a great episode for Myth Busters.  They could start with
trying the freezer thing and either corroberating or debunking it.  In the
end they could have a lot of fun abusing the cells more and more until they
go boom.  It would be interesting to see how much abuse they really take,
and it would be fun to watch.


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com

2005\06\22@223411 by Russell McMahon

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face
{Quote hidden}

It's not. But it was stated as personal experience by a list member. If waving a dead fish was found to fix dead batteries it could be reported. If freezer-ising did, it too can be reported. Small sample sizes are not good for drawing solid conclusions from, but practical experience is worth at least noting rather than just rejecting out of hand.

> In this case however, I'd stay away.  Lithium batteries have the
> nasty habit
> of catching fire and taking the nearby surroundings with them.
> These are
> not things to handle outside published specifications without taking
> some
> serious precautions.

Published specs will vary with manufacturer, and frezer temperatures will also vary and are usually unknown, BUT storage temperature specs for Li Ion battteries are around or below the level liable to be encountered in a freezer. (But may not be in individual cases :-) ).

It's hard to quickly find minimum stirage temperature specs, but here's some quidelines.

eg

1.    -20C
           http://support.radioshack.com/support_tutorials/batteries/bt-liion-main.htm

2.    -20C
Moli Energy Lithium Ion Battery Storage: Storage temperature range is -20 to 60° C. Recommended storage voltage range is 4.1 to 2.0 volts per cell. For prolonged storage periods, store discharged [i.e. 2.0 to 3.0 volts per cell] and at -20° to 25° C.

       http://www.powerstream.com/Storage.htm

3.    Eveready L91 Lithium

This is NOT directly related but is interesting. Storage and operating = -40C to +60C.



           RM

2005\06\23@041933 by Alan B. Pearce

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>This would make a great episode for Myth Busters.  They
>could start with trying the freezer thing and either
>corroberating or debunking it.  In the end they could have
>a lot of fun abusing the cells more and more until they
>go boom.  It would be interesting to see how much abuse
>they really take, and it would be fun to watch.

Especially when one is the other side of a TV set, and some poor disposable
camera is close enough to get caught in the firestorm. ;))

2005\06\23@101225 by Mike Hord

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> There is anecdotal evidence from other sources who claim to have had
> firsthand success regenerating Li Ion batteries by this means. (Google
> knows).

The other thing to take into account is that this method was
almost certainly not fallen into by happenstance; i.e., someone
wasn't looking for a place to store their dead battery and stuck it
in the freezer, wrapped up in kitchen foil, then forgot about it for
a few days, after which they discovered it while looking for a cod
fillet and decided to give it a try.

It was done because someone with some degree of knowledge
about the topic thought it might help, and tried it, and maybe it
even did help.

Mike H.

2005\06\23@163152 by Peter

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I do not know what the fridge does to Li batteries but it can revive
NiCd and anything that has water-based electrolyte and failed 'dry'
(usually by electrolyte migration of seomthing like that).

Peter

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