# what is REALLY the ideal storage voltage of li-ion batteries?



## xchcui (Nov 23, 2015)

Hi.

I read alot of articles and each one mentioned a different
ideal storage voltage for li-ion batteries.
Most of the places mention that the capacity should be 40%,but each one gave different voltage.
One says 3.82V other says 3.7V,third one says 3.6V etc.
In wikipedia https://en.wikipedia.org/wiki/Lithium-ion_battery#Self-discharge)
they recommended not more than 3.6V.


> ...Storage of a battery charged to greater than 3.6 V initiates electrolyte oxidation by the cathode and induces SEI layer formation on the cathode...


And at the "lithium ion technical handbook":
https://cdn.sparkfun.com/datasheets/Prototyping/Lithium Ion Battery MSDS.pdf
It mentioned that the best storage voltage is 3.3v 
see figures 20 and 21.
Even though keeping the battery in storage at 3.3v seems to be too low(as they could drop to the unwanted low voltage during long storage),the main point is,as i can understand from those graphs,is that lower storage voltage(as low as 3.3v) is better than 3.6v,3.7v or 3.82v(whatever 40% capacity refer to).
Does someone,but only the experts among you,that know without a doubt:
What is REALLY the ideal storage voltage of li-ion batteries?:shrug:

Thanks in advance.


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## dssguy1 (Nov 23, 2015)

I think the 3.82 came from the voltage you should stop the charger at if you want it to drop back to the correct storage voltage. 

Beyond that, I don't know! Looking forward to my SkyRC MC3000 so I can set a charge termination voltage for storage. Instead of having to hawk over my VP2 all the time.


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## TinderBox (UK) (Nov 23, 2015)

Does the cell being protected make a difference, does the protection circuit use enough power to risk having a below 2.5v when left in storage at 3.6v

John.


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## xchcui (Nov 23, 2015)

dssguy1 said:


> I think the 3.82 came from the voltage you should stop the charger at if you want it to drop back to the correct storage voltage...


The 3.82V is the open circuit voltage after the battery
rests 90 minutes minimum.


TinderBox (UK) said:


> Does the cell being protected make a difference, does the protection circuit use enough power to risk having a below 2.5v when left in storage at 3.6v
> 
> John.


I took into account that the battery loosing some power by the protection
circuit besides the self discharge rate.
But this is one,among the other value that i mentioned, according to a different recommendation at differents articles.
And those,different values, are the reason that i looking for a reliable value from and really 
expert that know for sure the right storage voltage.


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## ChrisGarrett (Nov 23, 2015)

Not saying it's an absolute ideal, but I go down to around 3.6v-3.7v, put them in plastic cases, then I seal them in a Ziplock baggie and into the fridge they go.

Works for me.

Chris


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## CuriousOne (Nov 23, 2015)

I have a bunch of Sanyo UR18650. According to date code, they were made 08.2004. They were never charged or used. They all measure in between 3.69-3.78 volts.


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## markr6 (Nov 23, 2015)

CuriousOne said:


> I have a bunch of Sanyo UR18650. According to date code, they were made 08.2004. They were never charged or used. They all measure in between 3.69-3.78 volts.



Wow that's old! It would be cool to see how those perform in a light-moderate drain.


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## kreisl (Nov 23, 2015)

xchcui said:


> It mentioned that the best storage voltage is 3.3v


3.3V resting offline voltage, really? wow.



dssguy1 said:


> Looking forward to my SkyRC MC3000 so I can set a charge termination voltage for storage. Instead of having to hawk over my VP2 all the time.


The mc3k parameter range for Storage 4.2V-Liion battery is {3.65|3.66|…|3.99|4.00}V so one would have to use the Discharge mode instead (plus the Discharge Reduce option) which covers the adjacent voltage range {2.50|2.51|…|3.64|3.65}V.


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## CuriousOne (Nov 23, 2015)

According to LiitoKala Li-260, they perform quite well, measure in between 1920-1980mAh.

(They were bought here: http://www.bgmicro.com/ur18650f-2000mah-rechargeable-lithium-ion-by-sanyo.aspx price then was $17.5 per pack of 10, so I grabbed 5 packs)


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## uofaengr (Nov 23, 2015)

Based on recommendations here, I store mine at 3.7V but just keep them in a drawer in their plastic case. I figure I receive them at 3.7V so it's good enough for me.


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## BringerOfLight (Nov 23, 2015)

Close to empty is ideal. At that point, there is no more self-discharge.

However, protection and battery gauge circuits have some parasitic drain. 5 uA is typical for a basic single-cell protection IC. A battery gauge IC will probably need 50-100 uA. 

When you have a protected cell or battery pack that's close to empty, it can easily become over discharged by that parasitic drain.


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## xchcui (Nov 25, 2015)

BringerOfLight said:


> Close to empty is ideal. At that point, there is no more self-discharge.
> 
> However, protection and battery gauge circuits have some parasitic drain. 5 uA is typical for a basic single-cell protection IC. A battery gauge IC will probably need 50-100 uA.
> 
> When you have a protected cell or battery pack that's close to empty, it can easily become over discharged by that parasitic drain.


This is what i was thinking of,but i wasn't sure.
So,i guess that the storage voltage should be between 3.6v-3.8v depend on the storage time.

Thanks.


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## ven (Nov 25, 2015)

Mine are mainly anywhere from 3.6v to 3.8v..........some are 4.1-4.2v for a quick change and i am not loosing sleep

So if i think they are not going to be used for a good time 6+ months for example, then around 3.6/3.8v, if to be swapped out in weeks or a couple of months even, they are fully charged.


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## MidnightDistortions (Nov 25, 2015)

BringerOfLight said:


> Close to empty is ideal. At that point, there is no more self-discharge.
> 
> However, protection and battery gauge circuits have some parasitic drain. 5 uA is typical for a basic single-cell protection IC. A battery gauge IC will probably need 50-100 uA.
> 
> When you have a protected cell or battery pack that's close to empty, it can easily become over discharged by that parasitic drain.



Wouldn't you need to have some charge in it? I know leaving NiMH cells discharged for too long can reduce the cycle life.. but i don't know if Li-ion cells have that same behavior near fully discharge levels.


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## Gauss163 (Nov 25, 2015)

CuriousOne said:


> I have a bunch of Sanyo UR18650. According to date code, they were made 08.2004. They were never charged or used. They all measure in between 3.69-3.78 volts.



If those are UR18650FM, then according to HKJ's table, 3.78V is about 40% SOC, so they were probably at very high SOC when you initially stored them. Do you know what voltages they were at when initially stored?


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## BringerOfLight (Nov 25, 2015)

MidnightDistortions said:


> Wouldn't you need to have some charge in it? I know leaving NiMH cells discharged for too long can reduce the cycle life.. but i don't know if Li-ion cells have that same behavior near fully discharge levels.


No. If you look at the Sony LiIon Technical Handbook linked in the OP, they have storage tests with completely discharged cells. I've seen similar tests elsewhere.


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## Gauss163 (Nov 25, 2015)

BringerOfLight said:


> I've seen similar tests elsewhere.



Links please.


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## AndyG (May 17, 2020)

BringerOfLight said:


> Close to empty is ideal. At that point, there is no more self-discharge.
> 
> However, protection and battery gauge circuits have some parasitic drain. 5 uA is typical for a basic single-cell protection IC. A battery gauge IC will probably need 50-100 uA.
> 
> When you have a protected cell or battery pack that's close to empty, it can easily become over discharged by that parasitic drain.



I can't see how that could possibly be true. SOC is hard to determine exactly but is near the 50% point, maybe as low as 40%. That's about 3.6-3.7 volts per cell, give or take a few percent. Near empty is at or below 2.5 volts and I definitely do not recommend storing that low, you will definitely damage the battery.


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