# Li-Ion Self Discharge Rate Test



## SilverFox (Apr 19, 2006)

On March 24, 2005 I charged an unprotected 18650 Li-Ion cell up to 4.000 volts and placed it in room temperature storage. A few hours later it was at 3.989 volts. 

On March 26, 2005 it was at 3.976 volts.

On May 14, 2005 it was at 3.975 volts.

On October 1, 2005 it was at 3.974 volts.

On December 11, 2005 it was at 3.973 volts.

On February 10, 2006 it was at 3.973 volts.

On March 2, 2006 it was at 3.973 volts.

On April 19, 2006 it is at 3.973 volts.

Not much in the way of self discharge...

EDIT: I tested this cell for remaining capacity, then charged it back up to 4.000 volts and checked the capacity again. After 1 year of room temperature storage, this cell had 95% of its original capacity. END EDIT

Tom


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## Mini-Moder (Apr 19, 2006)

I was just wondering about this today. Very useful thanks SilverFox.


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## TomBrown (Apr 19, 2006)

I look forward to seeing the 15 year graph on that one.


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## MrAl (Apr 19, 2006)

Hi again Tom,

Didnt we establish at one time that the charge is not related to the
open circuit voltage? On the other hand, it's also hard to believe
that the charge could change that much and not even show one
millivolt of change in the open circuit voltage. I dont know for
sure though because i have no graphs in front of me.

Take care,
Al


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## SilverFox (Apr 20, 2006)

Hello Al,

Li-Ion is similar to lead acid in that you can get an approximation of the state of charge by measuring the resting open circuit voltage.

Tom


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## Phaserburn (Apr 20, 2006)

This makes me even happier about my li-ion lights, like the Strion.


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## WAVE_PARTICLE (Apr 20, 2006)

that sounds great, but how does this compare to other rechargeable chemistries like NiMH and NiCd?

Thanks for the data!! :thumbsup:

WP


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## LEDcandle (Apr 20, 2006)

There have been a couple of threads on NiMh discharge rates; it is approx 2% a day. I don't know where they bottom out (0.8v - 1v?) though and whether they discharge all the way to that bottom.

My Li-ons don't discharge much either; I was mentioning in another thread, for those folks that let their fresh-from-charger Li-ons sit for a few days in hopes that they will drop from 4.2v to 3.7v so that they can use their Li-ons in a 7v light, *pls note* Silverfox's findings as that doesn't happen


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## WAVE_PARTICLE (Apr 20, 2006)

Wow....what a difference!

Assuming that the laws of thermodynamics are obeyed, am I correct to assume that the lost energy is in the form of heat generated by the battery? Just wondering, that's all....

WP




LEDcandle said:


> There have been a couple of threads on NiMh discharge rates; it is approx 2% a day. I don't know where they bottom out (0.8v - 1v?) though and whether they discharge all the way to that bottom.


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## changsn (Apr 20, 2006)

I thought there was a concern that although the voltage is essentially the same, that the capacity of the battery may have diminished considerably. When were you planning on doing a discharge?

Sam


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## SilverFox (Apr 20, 2006)

Hello Sam,

You are confusing Nickel chemistry with Li-Ion chemistry.

Tom


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## changsn (Apr 20, 2006)

Tom - I thought Li Ions do not like to be at full charge and their longevity is affected hence the store at half charge recommendation. So I was thinking that if this battery has been at full charge for over a year, is it fair to assume that the capacity is still there and on discharge the full mah would be seen. I know that NiMH batteries would not hold the voltage for this period of time due to self discharge - even the Eneloop.

Sorry if I am way off base here...
Sam


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## SilverFox (Apr 20, 2006)

Hello Sam,

The recommendation is to store Li-Ion batteries at around 40% charge. However, there is much (heated) debate over this. Some have stored their cells at full charge for extended periods of time without any noticeable decrease in cell performance. Others keep their cells at 40% until just before they use them, then discharge them back down after use. 

I was curious about this and for this test decided to charge up to about 75% and let things go from there.

Tom


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## ofcjim40 (Apr 20, 2006)

On a side note, how does heat and cold affect the discharge rate. As an example, I have a SF 9P running off of two unprotected 17500's as a backup light in my duty bag (I'm a Cop). My duty bag ends up in my personal car between shifts, so the light will be exposed to the changing environment in a car. So I'm sure at times the temp will be above 110 degrees in the car, etc on a very hot summer day. I usually charge the batteries in this light once a week (it is rarely used). Am I putting the bateries in danger or is this no biggie? Thanks.


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## SilverFox (Apr 20, 2006)

Hello OfcJim,

As long as the battery temperature remains below 140 F, you should be OK.

Tom


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## MrAl (Apr 20, 2006)

Hello again Tom,

That's great as the light i use most uses an Li-ion too.

Take care,
Al


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## NotRegulated (Apr 20, 2006)

ofcjim40 said:


> On a side note, how does heat and cold affect the discharge rate. As an example, I have a SF 9P running off of two unprotected 17500's as a backup light in my duty bag (I'm a Cop). My duty bag ends up in my personal car between shifts, so the light will be exposed to the changing environment in a car. So I'm sure at times the temp will be above 110 degrees in the car, etc on a very hot summer day. I usually charge the batteries in this light once a week (it is rarely used). Am I putting the bateries in danger or is this no biggie? Thanks.



I have been letting my TL3 with 17500's sit in my car overnight every night for months. I am amazed that the charge in the batteries still is maintained and the light works great. Nothing scientific to back this up. Night time temps in the Winter are mid 30's to 40's, and daytime temp (car in covered parking) is 75. Later at home it's 90-100 inside the car. I keep three primary 123's also in the car with the light as well.


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## Brighteyez (Apr 20, 2006)

Unless you're leaving the windows wide-open on the car during the day, chances are that the internal temperature in a locked car sitting in the sun during one of those real hot August days, are probably more like 130º-140ºF.

I've always chuckled when people ask me if the cold winters in Chicago were difficult, and I always reply that it was the summers (with humidity) that bothered me most. 



ofcjim40 said:


> So I'm sure at times the temp will be above 110 degrees in the car, etc on a very hot summer day.


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## SilverFox (Apr 20, 2006)

I have added the discharge testing data to the first post. In 1 year, this cell had 95% of its remaining capacity left.

Tom


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## changsn (Apr 20, 2006)

Thanks Tom, would you infer that storage is not as big a deal as the mfg ers seem to think? Perhaps too big a leap to make on one data point...
Sam


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## cave dave (Aug 31, 2006)

Will a "Protected" cell discharge faster? I understand the protection circuit uses some energy, but maybe that is only during use.


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## SilverFox (Aug 31, 2006)

Hello Cave Dave,

It is my understanding that a protected cell will have a slightly higher self discharge rate. I haven't done any formal testing, but when I got the 18650 battery holders for my LionHeart I put my smaller pila cells and holders in storage. I think it has been over a year now and they are still at over 3.8 volts. I believe they were put into storage at around 3.85 volts.

Tom


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## faucon (Sep 1, 2006)

SilverFox said:


> Hello Cave Dave,
> 
> It is my understanding that a protected cell will have a slightly higher self discharge rate. I haven't done any formal testing, but when I got the 18650 battery holders for my LionHeart I put my smaller pila cells and holders in storage. I think it has been over a year now and they are still at over 3.8 volts. I believe they were put into storage at around 3.85 volts.
> 
> Tom


Tom, thanks very much for this info. It turns out that I've been needlessly worrying about my Pilas and AW protected cells self-discharging as quickly as my Nimh cells do. It's *great* to see that I can keep extra charged cells around, and lights that I haven't used much in weeks or even months, and can still expect them to perform very well. 
:goodjob:


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## paulr (Sep 2, 2006)

I don't think a test on a brand new cell gives you complete info on a cell that's been used for a while. I've noticed cell phone and digicam batteries start to self-discharge once they get older.


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## SilverFox (Sep 3, 2006)

Hello Paul,

These cells are used... The unprotected 18650 has over 200 cycles on it and the Pila cell has over 100.

Tom


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## Glen C (Dec 12, 2006)

SilverFox, thank you for this, it is a great experiment


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## MrAl (Dec 13, 2006)

Hi there,

I am not one to believe in voltage tests alone, but i have to admit that i have
an 18650 light that i dont use that much any more since i got my Li-ion AA
cell light together, and yet every time i pick it up (maybe a year now since
last charge) it still shines brightly.


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## InfidelCastro (Dec 13, 2006)

If you want the charge on your NIMH batteries to last like a lithium-ion, put them in a little baggy and in the freezer shortly after charging.

This works great! I have tested charge NIMH's that were put in the deep freeze at well over 1.4V months later.


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## Concept (Dec 13, 2006)

I'll just move the chocolate icecream to the top shelf and put the frozen peas in the door!


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## InfidelCastro (Dec 13, 2006)

Yea, I just have a junky little half sized fridge with a plastic sleeve separator for the freezer section. I'll bet it works even better in an actual freezer or a decent fridge with a separated freezer section.


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## TooManyGizmos (Dec 13, 2006)

MrAl said:


> Hi there,
> 
> I am not one to believe in voltage tests alone, but i have to admit that i have
> an 18650 light that i dont use that much any more since i got my Li-ion AA
> ...


:laughing:

Well .................... There ya go ............


................ TMG/
.


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## bxstylez (Dec 13, 2006)

when u take it out of the freezer, can u use it right away or wait for a certain amount of time before putting them under load?





InfidelCastro said:


> If you want the charge on your NIMH batteries to last like a lithium-ion, put them in a little baggy and in the freezer shortly after charging.
> 
> This works great! I have tested charge NIMH's that were put in the deep freeze at well over 1.4V months later.


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## Mike abcd (Dec 13, 2006)

Use the refrigerator, not the freezer. The freezer is way colder than advised for storage. The frig will cut self discharge dramatically over room temp storage. 

Allow the cells to get near room temp before putting them into anything to avoid condensation in it. best approach is keeping them in zip lock bags until they're warmed back up a bit but for single cells, wiping them off after their warm before use is good enough.

Mike


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## Anders (Dec 13, 2006)

According to Sanyo it is ok to store them down to - 20 C.

http://www.sanyo.com/batteries/pdfs/twicellT_E.pdf


Anders


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## Mike abcd (Dec 13, 2006)

Anders said:


> According to Sanyo it is ok to store them down to - 20 C.
> 
> http://www.sanyo.com/batteries/pdfs/twicellT_E.pdf
> 
> ...



That's for NiMH. Duracell lists the same for their NiMH as "Permissable" but says "10°C to 30°C (50°F to 86°F)" as "Recommended" so even the frig is below that.
http://www.duracell.com/oem/rechargeable/Nickel/nickel_metal_tech.asp
http://www.duracell.com/oem/Pdf/others/TECHBULL.pdf

They have some interesting data on Li primary (Li/MnO2). I don't think they sell LiOn at least in "consumer" apps.
http://www.candlepowerforums.com/vb/newreply.php?do=newreply&p=1733566

Haven't had a chance to look for Sanyo LiOn storage info.

Mike


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## tron3 (Dec 13, 2006)

Now that is commitment. Thanks SilverFox.

I have an R-CR123 in my Fenix P1. I believe I last charged it at th beginning of the year. I rarely use it, but the voltage is still high and holding.

I'm dying for Lith-Ion rechargeable AA's. Anyone know if they exist and where I can get them?


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## LowTEC (Dec 13, 2006)

tron3 said:


> Now that is commitment. Thanks SilverFox.
> 
> I have an R-CR123 in my Fenix P1. I believe I last charged it at th beginning of the year. I rarely use it, but the voltage is still high and holding.
> 
> I'm dying for Lith-Ion rechargeable AA's. Anyone know if they exist and where I can get them?



Check FifthUnit.com, qualitychinagoods.com or our own member "AW" for 14500 cells, they are rated at 3.7V though


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## Gene (Dec 13, 2006)

In my experience, UNPROTECTED Li-Ions are the kings for ultra long term storage. However, PROTECTED Li-Ion cells will lose their charge faster.


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## combatative31 (Jul 9, 2008)

I have just bought a fenix tk11 which takes the 18650 protected battery i cant wait till it reaches the uk. Would the 18650 battery still hold charge as well if it were in a torch and not used?


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## TooManyGizmos (Jul 9, 2008)

Yes ...... it will.





combatative31 said:


> I have just bought a fenix tk11 which takes the 18650 protected battery i cant wait till it reaches the uk. Would the 18650 battery still hold charge as well if it were in a torch and not used?


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## kurni (Jul 9, 2008)

Oh wow; I was wondering about this; thanks


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## Burgess (Jul 9, 2008)

Wow, yet another great thread by SilverFox.

:twothumbs



Even though this thread is 2+ years old,
it still has lots of valuable data.


Thank you for your time, effort, and dedication ! ! !


:goodjob::thanks:
_


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## TooManyGizmos (Jul 10, 2008)

:tinfoil:... true .... it's an old thread.

But I thought someone had better give the guy an answer .....\/

So he doesn't get *combatative* ........

his user name might prevent some from answering.

I hope he's not a *bully* ..... too.





combatative31 said:


> I have just bought a fenix tk11 which takes the 18650 protected battery i cant wait till it reaches the uk. Would the 18650 battery still hold charge as well if it were in a torch and not used?


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## kurni (Jul 10, 2008)

TooManyGizmos said:


> :tinfoil:... true .... it's an old thread.


 Satisfied my curiousity; I'm happy 



TooManyGizmos said:


> But I thought someone had better give the guy an answer .....\/
> 
> So he doesn't get *combatative* ........
> 
> ...



so the 18650 is only to add momentum to TK11


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## TooManyGizmos (Jul 10, 2008)

..
:tinfoil:... Yeeeeeeoooooowwwww ... right over my head.


Sorry kurni ....... I just didn't get it



Yur not gonna get *combatative* on us too .... are ya kurni ?
.


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## kurni (Jul 10, 2008)

:lolsign: 18650 only to add weight to TK11 hence adding momentum during striking. Most of the time no need to turn on TK11 during close-range combat; hence the question if 18650 will lose charge when not used


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## TooManyGizmos (Jul 10, 2008)

..
:tinfoil:... YYeeeeeeeeoooooowwwwwww ......


If you say so



.


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## brighterisbetter (Nov 8, 2008)

for a VERY informative thread that every 'newb' should read before starting a new one.


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## chewy78 (Jan 4, 2009)

\


brighterisbetter said:


> for a VERY informative thread that every 'newb' should read before starting a new one.


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## Tempsho (Sep 10, 2009)

Gene said:


> In my experience, UNPROTECTED Li-Ions are the kings for ultra long term storage. However, PROTECTED Li-Ion cells will lose their charge faster.


 
I agree. I have a blue, ebay no-name 2400 mAh unprotected 18650 battery. I haven't charged it in months, and when I checked the voltage of it today, it was sitting at 4.17 volts. I don’t use it much because I have 2, protected AW 18650's that I use regularly in my T10L, but it's good to know that if I have to use the unprotected one in a pinch it will do the job. (for a little while at least until I get the AW’s charged up)

I always use a good quality $700 Fluke 289 True RMS Data Logging Multi Meter to test my batteries. I’m a Power Electrician by trade and my work provides me with sweet meters!


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