BU-802b: What does Elevated Self-discharge Do?

Learn about an often ignored characteristic of batteries

All batteries are affected by self-discharge. Self-discharge is not a manufacturing defect but a battery characteristic; although poor fabrication practices and improper handling can increase the problem. Self-discharge is permanent and cannot be reversed. Figure 1 illustrates self-discharge in the form of leaking fluid.

Effects of high self-discharge

Figure 1: Effects of high self-discharge.

Self-discharge increases with age, cycling and elevated temperature. Discard a battery if the self-discharge reaches 30 percent in 24 hours.

Courtesy of Cadex


The amount of electrical self-discharge varies with battery type and chemistry. Primary cells such as lithium-metal and alkaline retain the stored energy best, and can be kept in storage for several years. Among rechargeable batteries, lead acid has one of the lowest self-discharge rates and loses only about 5 percent per month. With usage and age, however, the flooded lead acid builds up sludge in the sediment trap, which causes a soft short when this semi-conductive substance reaches the plates. ( See BU-804a: Corrosion, shedding and Internal Short )

The energy loss is asymptotical, meaning that the self-discharge is highest right after charge and then tapers off. Nickel-based batteries lose 10–15 percent of their capacity in the first 24 hours after charge, then 10–15 percent per month. Figure 2 shows the typical loss of a nickel-based battery while in storage.
 

Self-discharge as a function of time

Figure 2: Self-discharge as a function of time.

The discharge is highest right after charge and tapers off. The graph shows self-discharge of a nickel-based battery. Lead- and lithium-based systems have a lower self-discharge.

Courtesy of Cadex


NiMH and NiCd belong to rechargeable batteries that have the highest self-discharge; they need recharging before use when placed on a shelf for a few weeks. High-performance NiCd has a higher self-discharge than the standard versions. Furthermore, the self-discharge increases with use and age, of which crystalline formation (memory) is a contributing factor. Regular full discharge cycles keeps memory under control. ( See BU-807: How to restore Nickel-based Batteries )

Li-ion self-discharges about 5 percent in the first 24 hours and then loses 1–2 percent per month; the protection circuit adds another 3 percent per month. A faulty separator can lead to elevated self-discharge that could develop into a current path, generating heat and, in an extreme case, initiate a thermal breakdown. In terms of self-discharge, lead acid is similar to Li-ion. Table 3 summarizes the expected self-discharge of different battery systems.
 

Battery system

Estimated self-discharge

Primary lithium-metal

10% in 5 years

Alkaline

2–3% per year (7-10 years shelf life)

Lead-acid

5% per month

Nickel-based

10–15% in 24h, then 10-15% per month

Lithium-ion

5% in 24h, then 1–2% per month (plus 3% for safety circuit)

Table 3: Percentage of self-discharge in years and months. Primary batteries have considerably less self-discharge than secondary (rechargeable) batteries.

The self-discharge of all battery chemistries increases at higher temperature, and the rate typically doubles with every 10°C (18°F). A noticeable energy loss occurs if a battery is left in a hot vehicle. High cycle count and aging also increase self-discharge of all systems. Nickel-metal-hydride is good for 300–400 cycles, whereas the standard nickel-cadmium lasts for over 1,000 cycles before elevated self-discharge starts interfering with performance. The self-discharge on an older nickel-based battery can get so high that the pack goes flat from leakage rather than normal use. (See BU-208: Cycling Performance demonstrating the relationship of capacity, internal resistance and self-discharge.)

Under normal circumstances the self-discharge of Li-ion is reasonably steady throughout its service life; however, full state-of-charge and elevated temperature cause an increase. These same factors also affect longevity. Furthermore, a fully charged Li-ion is more prone to failure than one that is partially charged. Table 4 shows the self-discharge per month of Li-ion at various temperatures and state-of-charge. The high self-discharge at full state-of-charge and high temperatures comes as a surprise. ( See also BU-808: How to Prolong Lithium-based Batteries )
 

State-of-charge

0°C (32°F)

25°C (77°F)

60°C (140°F)

Full charge

40–60% charge

6%

2%

20%

4%

35%

15%

Table 4: Self-discharge per month of Li-ion at various temperatures and state-of-charge
Self-discharge increases with rising temperature and higher SoC.

Lithium-ion should not be discharged below 2.50V/cell. The protection circuit turns off and most chargers will not charge the battery in that state. A “boost” program applying a gentle charge current to wake up the protection circuit often restores the battery to full capacity. ( See BU-803a: How to Awaken Sleeping Li-ion )

There are reasons why Li-ion is put to sleep when discharging below 2.50V/cell. Copper dendrites grow if the cell is allowed to dwell in a low-voltage state for longer than a week. This results in elevated self-discharge, which could compromise safety.

Self-discharge mechanisms must also be observed in manufacturing. They vary from corrosion to impurities in the electrodes that reflect in self-discharge variations not only from batch to batch but also form cell to cell. A quality manufacturer checks the self-discharge of each cell and rejects those that fall outside tolerances.

Figure 5 compares the self-discharge of a new Li-ion cell with a cell that underwent forced deep discharges and one that was fully discharged, shorted for 14 days and then recharged. The cell that was exposed to deep discharges beyond 2.50V/cell shows a slightly higher self-discharge than a new cell. The largest self-discharge is visible with the cell that was stored at zero volts.
 

Self Discharge of Li-ion
Figure 5: Self-discharge of new and stressed Li-ion cells. Cells that had been stressed with deep discharges and kept at 0V show a higher self-discharge than a new cell.
Source: TU München
 

Last Updated 2016-08-13


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Comments

On December 3, 2011 at 7:26am
John Fetter wrote:

Self discharge is generally caused by impurities. In the case of lead-acid, it is feasible to keep impurities from causing excessive self discharge. This is done by using a suitable chemical substance that prevents the impurities, that inevitably migrate via the electrolyte, reaching the negative plates.

Impurities are present in the negative plates at the time of manufacture, however, they get buried in the negative active mass over time. The impurities in the positives and that are put in the electrolyte with the filling water just keep electroplating out onto the negatives.

These “electroplating” impurities can be stopped by that chemical substance. After about three months in service, the battery ends up with near-zero self discharge.

On December 18, 2011 at 4:56am
Tom Tercek wrote:

This is the best website on batteries, thank you so much..
I have been wondering what the difference is between “precharged”
NIMH vs standard NIMH batteries.
What are the pros and cons of these 2 types??
Thanks

On February 1, 2012 at 8:03pm
Kenny wrote:

So, do you charge your phone to 100percent or charge it only to 80 percent and use it down to 20 percent and recharge again ?

On February 14, 2012 at 12:59pm
tytower wrote:

Comment 1 -John Fetter - So what is that suitable chemical substance then ?

Tom Tercek- I notice precharged is marked on more recent rechargeables because the have lower self discharge . Standard rechargeables seem to be flat in 1 to 3 months max. The precharged seem to last many months of non use before needing recharge.

On February 14, 2012 at 1:30pm
John Fetter wrote:

tytower:  The source and preparation of this material was revealed on, “How to Prolong Lead-acid Batteries”, Dec 8, 2011 at 3:12 am, (a parallel page on this website). You can find more info. scattered about on various pages.

On May 9, 2012 at 9:22pm
Richard Britton wrote:

Thanks for the wealth of Info on self discherge od secondary batteries.  Much of it, I’ve not seen before, and I’ve been working with batteries about 65 years. 
I would like to find a very low self discharge battery, 6 volt, Group 1 for use in antique cars dating back to the teens. Often they sit unused for years.  They should also have a long useful life (eg. 10 to 30 years). Use of a trickle charger is no problem.

On June 6, 2012 at 3:51am
Valentin Lecuyer wrote:

Thanks for all the infos.

I am facing a big problem of Self-Discharge in a CR2 (Lithium Prinary) battery : When I use it for 75% of its capacity, in less than a day, the 25% left disapear by Self-Discharge.
Does anyone knows about this problem?

Thanks

On April 15, 2014 at 4:48pm
danwat1234 wrote:

I am curious how the chip inside the battery pack of a laptop accounts for self discharge. For instance if you leave the laptop off for long periods of time unplugged and off (weeks) or leave the battery out of the laptop for weeks or months. When you start up the laptop again and pop in the battery I think it’s smart enough to immediately give the updated, perhaps semi-accurate charge % so it accounts for the self discharge somehow? It can looks at instantaneous voltage readings and changes with load.

Does the chip log history so it knows the behavior of the battery so it doesn’t need to be calibrated when you let the battery self discharge, looking at voltage and maybe resistance and it knows immediately?

Thanks

On April 18, 2014 at 2:44am
Ben Smit wrote:

Good day,

I have n lithium polymer battery that discharge in 2 days.

I do laser alignment. So I have 2 components.  One is n receiver and the other one n laser.

I have to charge to laser every time before I go and work. Say I did not work for 2 days. The laser discharge by it self. But the receiver sits on 90%.

Whats wrong with the laser battery? Why is it losing its charge?

On May 26, 2014 at 1:39am
Madhav wrote:

Is there any possiblity to reduce self discharge of Lead acid batteries.

On May 26, 2014 at 2:24am
John Fetter wrote:

Madhav - Yes, there is. Please refer to my posts on Additives to Boost Flooded Lead Acid, dated Jan 8, Jan 13 and May 25, 2014.

On August 21, 2014 at 8:11pm
Edward wrote:

John Fetter— are you the Lead-Acid experter???

On August 21, 2014 at 11:09pm
John Fetter wrote:

Edward - Are you Swedish?

On August 22, 2014 at 1:41am
Edward wrote:

John Fetter—No i am a ni battery engineer from China, my email is zzrm316@163.com . keep in touch please

On August 22, 2014 at 5:53am
tom wrote:

great battery site

On August 25, 2014 at 11:19pm
John Fetter wrote:

Edward - You might like to explain why.

On November 6, 2014 at 4:47am
John wrote:

Hello, I just found this excellent website.

Question re.  self discharge (particularly Li-Ion). I presume that the specified discharge rates are based on cells which are not connected / on the shelf. And wonder if/how taking a small amount of current from the cell (c. 50-100 uA) would effect the self discharge characteristics.

The reason for asking this is that I recall a supplier comment some time ago regarding Li-SOCl2 primary cells, which suggested that a small continuous current excited the chemistry sufficiently to reduce the effects of self discharge.

On November 6, 2014 at 5:33pm
Edward wrote:

Hi John ,Do you mean you want to charge the Li-SOCI2 primary cells at very small current??

On November 7, 2014 at 3:55am
John wrote:

Hi Edward.
No, we currently use Li-SOCI2 primary cells in an application which has a small continuous current drain, and are lead to believe that this can improve the life (as it excites the chemistry).
What I was asking was if a similar continuous current would have any positive effect on Lithium-Ion battery’s and possibly help the comparatively poor self discharge characteristics. My understanding following the post yesterday is probably not :-(

On November 8, 2014 at 6:32pm
Edward wrote:

keep in charging the Lithium-ion battery at small current long time?  the over-charge to Lithium-ion battery will damage it

On January 12, 2015 at 7:05pm
Randy wrote:

This is a great site, and this topic a real eye opener. When I first discovered LiPO cells I was ecstatic about their energy capacity, but soon came to realize how much extra care they needed. My latest concern was in a project involving a 200maH LiPo. I had a good charging circuit, but not such good protection against over discharge. In trying to solve that with a home brewed protection circuit, i realized that you can not make a low voltage cut off circuit that draws zero current, a paradox since a LiPO is easily ruined by over discharge. At least this page helped me put it in perspective. seems if I can get my protection circuit to contribute less than 3% of the self discharge, I’m already doing better than a lot of the built in protection circuits.

On August 12, 2015 at 1:52am
changhangxom wrote:

Hi, dear all.
I want to find chart of battery dischart, battery capacity after a period of using. Who do you have? Please give me
Thank you very much

On November 10, 2015 at 10:00pm
Gajender wrote:

I have required a low self discharge battery for remote location area without any charging.
Application…...gsm based data transmitters
Volt ...9-12vdc
Load…..50ma constantly and 1A for 1 minutes twice in per day
Required life ...minimum 5 year
Please suggest which should I use

On November 29, 2015 at 9:31am
petey pablo wrote:

If my new battery from my phone arrived in a 1% state and it was left in the warehouse for 3 months according to this article the self discharge would be greater esp if it’s been in a low voltage state less than 2.5V. I understand the protection circuit switches the battery off so it doesn’t fall below this low level but if it is at a 2.5V state in storage for 2-3 months the self discharge is how bad you reckon?

On January 6, 2016 at 8:42am
Robert Kostecki wrote:

Gajender,

If “no charge” then Alkaline 2-3% per year (7-10 years shelf life, according to the article.

Capacity

5 years x 356 days x 2 minutes / 60 minutes = 61 Ah (transmit)
+ 5 years x 365 days x 24 hours x 0.05A = 2190 Ah (standby)

You would need 2650 Ah (!!) battery pack assuming 15% self discharge. You need 1.25 Ah daily. Why don’t you use a small solar powered charger with 6Ah rechargeable system?

On January 6, 2016 at 9:19am
John Fetter wrote:

Gajender, Robert - There is no commercial battery that will reliably deliver 50 mA constantly and 1 A for one minute twice a day, for five years. There may be an exotic battery costing a very large sum of money that will work. Solar is obvious, evidently not considered. Which means the objective is for the equipment to remain “invisible”.

On January 6, 2016 at 10:01am
Randy Constan wrote:

For anyone interested, I have a small (3 component ) circuit you can build for cutting off the current flow from a single lithium-ion (or LiPO) cell to prevent overdischarge. Unlike most circuits that are built into higher priced cells, this one is designed to cut off at about 3.0V instead of the more typical 2.5, which IMHO sacrifices very little usable charge and better protects a cell. I’ve included a link to my site where I wrote the article, which actually uses this page as a reference at one point. I hope this is OK with the moderators.

http://elfintechnologies.com/liIonProtect.html

Incidentally, a not to Mr. Gajende’. You might want to touch base with me using the CONTACT from on that same website I linked, and explain more about your project. I tend to agree with the comments of others, that some backup solar charging might make for a smaller power pack for the longevity you need, but I may be able to help you think out a solution.

On February 15, 2016 at 4:50am
Ahmad wrote:

i would like to know for how longcan i store the battery without losing its efficiency.
I mean if i had to to store 2V batteries in awarehouse without charging them, for how long do these battereis maintain their efficiency in this case?

On February 15, 2016 at 5:28am
John Fetter wrote:

Ahmad - Depends entirely on temperature. If it gets very hot, you will begin to damage the cells within a few months.  I suspect the reason why you ask is because your warehouse gets very hot. The only way to store batteries is to keep them cold. As cold as possible. Charging batteries that are being kept in a hot warehouse is not a good way to solve the problem.

On March 30, 2016 at 5:33pm
Wayne Ahlers wrote:

I have a Roadtrek RV that uses a Tripplite inverter charger.
Overnight the battery voltage will drop from 12.6 to 11.1 with no known loads, the charger may have a few 10’s of MA idle current.
Plug in shore power and it will charge for about five minutes, the charger will cut off,  and then be back at 12.6.
It has no capacity, a 10 amp load will drop to 11.1 in a few minutes.
It is a brand new USBattery sealed AGM 100 amp hour.
Dealer has removed and recharged battery and says it is fine.
Can any body tell me what is going on here?

On March 30, 2016 at 7:25pm
Randy Constan wrote:

Wayne—-If you Google up “Li-Ion discharge curves”, and look at a few of the graphs you find, you’ll quickly discover that the normal discharge of any Li_ION type battery includes a fairly rapid decline from the max of 4.2V/ cell, to about 3.8. At that point the discharge curve is a near flat slow decline until you get to around 3.5V, and then it drops very quickly. So a freshly charged 3 cell Li-ION battery should indeed be about 4.2 x 3, or 12.6v. But it doesn’t take much to make it drop to 3.8 x 3, or 11.4V. Self discharge can be part of it, and the self protection circuitry built into most quality cells these days can actually contribute a little more. I’d suggest you consider it normal for the load you described to drop the amount you described. if the battery is indeed good, even though it seemed to lose over a volt in 10 minutes, you SHOULD find that the same load will take another 10 hours or more to drop another volt, because that is the nature of the way these batteries discharge. On the other hand if you find it declines much faster then that, you’ll need to demand your money back. :-

On March 30, 2016 at 7:27pm
tom tercek wrote:

It sounds like a bad battery. I may have been overcharged and lost some electrolyte. AGM batteries do not have excessive electrolyte and long term floating at too high a voltage can ruin them. A good load test should reveal the health of the battery.
The fact that it charges to good open circuit cell voltages may be what the dealer used as a criteria for battery condition.
I would insist the dealer load test the battery and compare the load test results with a new battery. I would guess that would show quite difference and you would have a case for a new battery. I am curious now so let me know what happens.

On March 30, 2016 at 7:32pm
tom tercek wrote:

My previous comment was directed to the Roadterk RV owner about the AGM battery. BTW Cadex makes some really good battery load testers etc.

On April 5, 2016 at 6:54am
igor wrote:

Hi,
do you have chart or graft for self discharge in 24 hours VS battery life time
to be more clear i want to test few tablet batteries, i want to measure self discharge and by that estimate battery condition.

On April 22, 2016 at 8:22pm
Mark wrote:

I have battery thats come from my old laptop. I try to recover it and re use the battery but when a single cell well charge it from 0 volts to 3.5v, but after 10 hours the voltage drops without load. What is suggestion its ok to used or not? Thanks for helping me.

On April 23, 2016 at 9:48am
Randy Constan wrote:

Mark - Based on your description, that cell sounds useless. Old laptop batteries are often not worth salvaging, for the very behavior you mentioned.

On April 27, 2016 at 12:32pm
Jim Reich wrote:

Hi. I’m a little uncertain on the definition of self discharge.

When a 1000 mA-h battery specs “1%/month self discharge” for example (at our operating temp, and assuming a well-treated happy battery), I understand that there is an initial drop off that looks somewhat exponential (which is new, interesting info—Thanks for this great site!).

But after that point, will the battery essentially drain at an average of 10 mA-h/month until it is nearly drained?

Or will it initially self discharge at 10 mA-h/month, and when it’s down to 500 mA-h left, it’ll drain 5 mA-h/month, and when it’s at 250 mA-h, self discharge will drop to 2.5 mA-h/month?

On April 27, 2016 at 10:27pm
Anand wrote:

Please advice-
What is the self discharge pattern for automotive lead-acid battery?
What will the discharge voltage in a month time for a fully charge 60Ah lead-acid battery?

On June 12, 2016 at 2:25am
Joan wrote:

For a Li-ion cell the self discharge is given as initial 5% and then 1-2% per month.

The datasheet for a Li ion cell from Samsung (ICR18650-30B) states a capacity of better than 80% after a month.
Wouldn’t you think they rather use 90-93% if those types of cells would be able to do that?

TLDR: I’m questioning the low self discharge for Li-Ion cells given in the article up there.

*) http://gamma.spb.ru/media/pdf/liion-lipolymer-lifepo4-akkumulyatory/ICR18650-30B.pdf

On June 23, 2016 at 12:24pm
Ben wrote:

The self discharge graph shows a loss of 7mV/day for a new Li cell.  Why is the graph showing voltage instead of amp-hour (Ah) loss? 

In self discharge, isn’t the issue amp-hours being lost?

On July 5, 2016 at 9:31am
Gideon wrote:

I ‘m using a netbook with Li-ion battery packs and I can only charge them ONCE every 7 days.

My “empty” packs still hold 10-20 % of charge and are sitting on the shelf at room temperature for several days before being fully recharged.

Will this practice reduce the lifespan of my battery packs ?

 

On September 21, 2016 at 10:20pm
Nick C wrote:

Hello.  Interesting read…I have an Acer Switch 11V convertible laptop that is “self draining” at the rate of 5-7% per day of being “off”.  If I leave it off for several weeks (which happens since I travel quite frequently), I’ll come home to a dead laptop.  Acer is aware of the issue, but says that 5-7% per day is “normal” and quite acceptable.  After reading your discussion of Li-ion self drain, I’m am convinced that they have either “bad cells” or “bad design” in this device. Would anyone care to comment on this to assist?  My email: necostanzo@gmai.com   Much thanks, Nick