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'[EE] Coin cells and peak current draw'
2010\11\02@114319 by Mark Rages

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(Adding tag)

I have often heard that drawing pulses of more than about 15 mA from a
CR2032 coin cell will permanently degrade its capacity.

But TI has done the experiment and claims up to 30 mA with minimal
change in battery capacity:

http://focus.ti.com/general/docs/lit/getliterature.tsp?literatureNumber=swra349

Battery internal resistance is still the enemy, though.  A big
capacitor can help hold up the voltage during the current peak.

Looks like all testing was at room temperature too, which seems like a
big limitation.  Also interesting is the difference between claimed
and actual performance. (spoiler: Sony good, noname bad).

Regards,
Mark
markrages@gmail
--
Mark Rages, Engineer
Midwest Telecine LLC
spam_OUTmarkragesTakeThisOuTspammidwesttelecine.com



-- Mark Rages, Engineer
Midwest Telecine LLC
.....markragesKILLspamspam@spam@midwesttelecine.com

2010\11\02@174853 by Stephen R Phillips

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Depends on the battery type. With a primary cell you dissipate some of the energy in the cell as well.  Lithium thionylchloride batteries for example do not like it one bit. However the standard CR2032 is manganese dioxide instead so its internal impedance isn't as severely impaired by large current draws.  
I suggest you ignore TI's claims. The main reason why is you should always go by the battery manufacturers specs. Since you cannot test the batteries without discharging them and possibly damaging them in the process you cannot test and sort for which battery will fail. Bottom line is the batteries are made to a spec and the manufacturer can change the battery beneath that spec any time as long as it meets the spec. This happens with rechargeable lithium ion batteries all the time. Although less likely with a lithium primary cell it's a possibility and your design may not work any longer.

Stephen

--- On Tue, 11/2/10, Mark Rages <markragesspamKILLspamgmail.com> wrote:

{Quote hidden}

> -

2010\11\02@201646 by William \Chops\ Westfield

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On Nov 2, 2010, at 2:48 PM, Stephen R Phillips wrote:

> The main reason why is you should always go by the battery  
> manufacturers specs.

Yeah, right.  Except for all the customers who are going to replace  that wonderfully spec'ed $4 Brand-name cr2032 cell with a no-name  import (that probably doesn't even have a spec sheet) at 1/10th the  price.  And who's to say under which circumstances that wouldn't be  the correct decision...

Certainly HUGE numbers of keychain LED lights have been sold that  overdrive their LEDs from over-discharged coin cells without a  consumer backlash about awful output and poor battery life...

BillW

2010\11\02@203847 by Mark Rages

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On Tue, Nov 2, 2010 at 4:48 PM, Stephen R Phillips
<KILLspamcyberman_phillipsKILLspamspamyahoo.com> wrote:
> Depends on the battery type. With a primary cell you dissipate some of the energy in the cell as well.  Lithium thionylchloride batteries for example do not like it one bit. However the standard CR2032 is manganese dioxide instead so its internal impedance isn't as severely impaired by large current draws.
>
> I suggest you ignore TI's claims. The main reason why is you should always go by the battery manufacturers specs. Since you cannot test the batteries without discharging them and possibly damaging them in the process you cannot test and sort for which battery will fail. Bottom line is the batteries are made to a spec and the manufacturer can change the battery beneath that spec any time as long as it meets the spec. This happens with rechargeable lithium ion batteries all the time. Although less likely with a lithium primary cell it's a possibility and your design may not work any longer.
>
> Stephen

What spec are you referring to?  I don't recall seeing max current
spec'ed by any coin cell manufacturer.

Note that even the cheapy no-name cells were not harmed by the 30 mA
peak current, at least at room temperature.

Regards,
Mark
markrages@gmail
-- Mark Rages, Engineer
Midwest Telecine LLC
RemoveMEmarkragesTakeThisOuTspammidwesttelecine.com

2010\11\02@220810 by Sean Breheny

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Unfortunately, battery manufacturers often give very optimistic specs,
too. For any application other than very simple, non-critical ones,
I've always had to test batteries in the actual application to be sure
what performance i was going to get. Anything critical can state that
it needs quality batteries and give a short list of acceptable ones.

Sean


On Tue, Nov 2, 2010 at 5:48 PM, Stephen R Phillips
<spamBeGonecyberman_phillipsspamBeGonespamyahoo.com> wrote:
{Quote hidden}

>> -

2010\11\03@120605 by RussellMc

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> Unfortunately, battery manufacturers often give very optimistic specs,
> too. For any application other than very simple, non-critical ones,
> I've always had to test batteries in the actual application to be sure
> what performance i was going to get. Anything critical can state that
> it needs quality batteries and give a short list of acceptable ones.

Be sure to have GoldPeak on your shortlist (GP) but beware clones.
Add BYd while there (My Buffet can't be wrong, right?).

I believe I have seen coin cells with max current specs.
Certainly larger formats almost always do.

Interestingly, rechargeable cell allowable trickle currents as a % of
1 hour capacity tend to rise with decreasing physical size until
allowable trickle is far larger than nominated fast charge rate.
Bizarre.



    Russel

2010\11\04@071327 by Jonathan Hallameyer

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> Interestingly, rechargeable cell allowable trickle currents as a % of
> 1 hour capacity tend to rise with decreasing physical size until
> allowable trickle is far larger than nominated fast charge rate.
> Bizarre.

With nickel cells, as long as the heat can get out trickle charge
current shouldnt be a problem correct?  So as you increase the ratio
of surface area to  volume (decreasing overall size) it should handle
a higher 'C' trickle charge.   Same as how some tool LiFe packs are
rated for many many C discharge, vs a large electric vehicle sized
pack couldnt push out the same C discharge because of heat not being
able to escape.
-- Jonathan Hallameye

2010\11\04@075425 by RussellMc

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> > Interestingly, rechargeable cell allowable trickle currents as a % of
> > 1 hour capacity tend to rise with decreasing physical size until
> > allowable trickle is far larger than nominated fast charge rate.

> With nickel cells, as long as the heat can get out trickle charge
> current shouldnt be a problem correct?  So as you increase the ratio
> of surface area to  volume (decreasing overall size) it should handle
> a higher 'C' trickle charge.

The argument sounds OK enough BUT at the top end with eg NimH AA
something has changed. One factor in being able to maintain a trickle
charge is the ability to recombine electrolysis products formed at the
electrodes. This requires catalytic material. It may be that as more
and more capacity is shoehorned into a fix package size the ability to
provide enough material that is not related to energy storage becomes
too difficult.

AA cells of over 2000 or so mAh from reputable manufacturers recommend
NO trickle charge or  low AND extremely short duration trickle charge.
This does  not appear to be a thermal issue. Gas formation and water
loss will both kill cells and both are exacerbated if recombining
catalysts are inadequate. The consequent venting will also expel
corrosive electrolyte.

The cube square law certainly seems to work at the bottom end with the
massive allowed trickle charge currents relative say to battery 1 hour
current capability - but this doesn't explain the immunity to
electrolysis. Presumably at low energy densities their is ample
volumetric capacity for catalytic material.


           Russell McMahon


'[EE] Coin Cells and Peak Current Draw'
2012\09\17@043805 by alan.b.pearce
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Came across this white paper from TI today, on peak current draw from coin cells, and thought of the OP who was asking about such things here recently ...


http://www.ti.com/lit/wp/swra349/swra349.pdf


-- Scanned by iCritical.

2012\09\17@080900 by RussellMc

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> On 17 September 2012 20:37,  <RemoveMEalan.b.pearcespam_OUTspamKILLspamstfc.ac.uk> wrote:
> Came across this white paper from TI today, on peak current draw from coin cells, and thought of the OP who was asking about such things here recently ...

> http://www.ti.com/lit/wp/swra349/swra349.pdf


Very useful reference

Main conclusions (read paper if these are of interest)

Stated max currents of 15mA for CR2032 found to be conservative - 30
mA usually OK
Loss in mAh capacity at 30mA compared to 15 mA is usually < 5%.

Adding a capacitor is biggest improvement in most cases.

Only Sony version managed labelled capacity at 30 mA. No name worst at
about 50% but GP also low. Usually rated capacity is specified at <<
30 mA.



Russel

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