IMR over-discharge

[Gauss163]

Now you have changed the discussion from overdischarged to severely overdischarged [...] Remember this discussion involves a single cell driven down to around 1.2 volts.

Not at all. I am simply discussing the matter in general. Whether or not that overdischarge is "severe" in the OP's context depends on many factors which we don't know.

This paper goes into the difference. It is interesting to note that for these particular cells "The cells under overdischarge that were terminated in Stage I exhibited no discernible changes in properties..." Stage I involved discharging down to 0 volts.

Did you forget that it was I who originally mentioned that paper here and discussed it at length? I see nothing there that provides scientific evidence supporting your proposed overdischarge safety test. Nor am I aware of any other scientific literature that would prove such a test to be generally reliable.

 

[SilverFox]

Hello Gauss163,

You stated..

"They found that cells that were not discharged past -12% (stage I, before the voltage starts rising due to copper dissolution), could be fully recharged and reused with "only minor side-effects" (confirmed also by SEM, XRD, and half-cell tests)."

This sounds reasonably scientific to me...

If there is minimal damage, the damage falls into the category of normal wear and tear that comes from use. When a cell falls below 80% of initial capacity it is time to recycle it. If the cell overheats during charging it is time to recycle it. If physical damage such as swelling is present it is time to recycle the cell. If you measure a lower than normal voltage after properly charging the cell it is time to recycle the cell.

If none of these negatives are observed, use the cell understanding the risks involved with stored energy.

Tom

 

[Gauss163]

You stated..

"They found that cells that were not discharged past -12% (stage I, before the voltage starts rising due to copper dissolution), could be fully recharged and reused with "only minor side-effects" (confirmed also by SEM, XRD, and half-cell tests)."

This sounds reasonably scientific to me...

I'm afraid you are misinterpreting the scope of the study. If you read the paper you will see that the point of the study was not to attempt to determine a general method of testing when an overdischarged cell remains safe for continued use. Rather, their aim was to find a quick method to induce internal short-circuits in cells that avoids the detriments of older methods (involving mechanical deformation or injection of foreign materials).

They didn't perform any of the tests that would be needed to infer more general results on safety, e.g. they didn't leave the cells overdischarged for long periods, nor did they test many different chemistries, nor did they do many subsequent cycles.

The literature is scarce on such topics so there is little scientific foundation to support any reliable general inferences on such matters. In fact they state in the paper that "The possible hazards of ISCr (internal short circuits) remain unknown due to the insufficient number of studies to reveal the entire overdischarge process".

Much is still not well-understood about how the chemistry affects these and related processes. That's why some researchers (e.g. Jeff Dahn at Tesla) have switched from theoretical to experimental techniques, e.g. randomly tweaking the chemistry to observe the impact is faster than making these inferences based on current incomplete theoretical models.

Given this lack of general knowledge on these matters it is wiser to be safe than sorry.

 

[SilverFox]

Hello Gauss163,

There is no misinterpretation of the scope of the testing. Having participated in thousands of tests I am always alert to the possibility of incidental findings that surface as a result of the testing process. The incidental observations in this case seem to match the observations of many that have spent time testing this chemistry. In addition they thought it important enough to include in the report.

Since it appears that there is no way for the average user to determine if a cell is damaged or not, we are left with some general observations with the understanding that stored energy has risks associated with it.

If the primary focus is risk, primary cells beginning to look attractive...

Tom

 

[Gauss163]

^^^ If you wish to convince me that your proposed overdischarge safety test works then you'll have to do much better than citing "general observations" from your personal experience. Scientific inferences require much higher standards of proof. On matters of safety we should accept no less.

I strongly discourage readers from using any of the above proposed tests to conclude that overdischarged cells are safe for continued use.

 

[IlluminationDomination]

Very interesting. I have observed these types of discussions prior to me becoming a member. iirc is was HKJ and Gauss163. I learned a lot from all the participants.

 

[recDNA]

I'd love to hear HKJ opinions on the issue.

 

[HKJ]

I'd love to hear HKJ opinions on the issue.

I generally prefer to follow manufacturer recommendations to minimize and risk:

http://lygte-info.dk/info/BatteryLowVoltage UK.html

I have thrown out some LiIon batteries used to test power bank without low voltage cut-out

 

[LichtAn!]

It's so cool to see you (HKJ) still active and rocking here, doing your battery tests. Always loved your website years ago when I first got into flashlights. :wave:

 

[HKJ]

It's so cool to see you (HKJ) still active and rocking here, doing your battery tests. Always loved your website years ago when I first got into flashlights. :wave:

I am still very active with 5-6 reviews each week on batteries, battery chargers, usb chargers, usb testers and recently I also started on multimeters. I only post batteries and battery chargers here, there are not really sections for the other stuff.

 

[peter yetman]

I generally prefer to follow manufacturer recommendations to minimize and risk:

http://lygte-info.dk/info/BatteryLowVoltage UK.html

I have thrown out some LiIon batteries used to test power bank without low voltage cut-out

The conclusion the that article should be a Sticky.
P

 

[HKJ]

The conclusion the that article should be a Sticky.
P

The article is probably already posted in this section, but older stuff can be hard to find.

 

[recDNA]

I read the entire thing including the last paragraph but failed to find a definitive throw away voltage? I saw below 1.5 but I would never charge a battery that dropped that low. I must be throwing away a lot of good batteries.

 

[HKJ]

I read the entire thing including the last paragraph but failed to find a definitive throw away voltage? I saw below 1.5 but I would never charge a battery that dropped that low. I must be throwing away a lot of good batteries.

This most definitive is this:

2) Do not charge batteries measuring below 2 volt, except if you have data saying it is safe.


"data saying it is safe" this means a datasheet listing a lower voltage.

 

[recDNA]

This most definitive is this:

2) Do not charge batteries measuring below 2 volt, except if you have data saying it is safe.


"data saying it is safe" this means a datasheet listing a lower voltage.

Thanks! I have always used any resting voltage below 2.5 V as a recycle right now voltage. I am being a little to conservative it seems.

 

[Gauss163]

I generally prefer to follow manufacturer recommendations to minimize and risk:

http://lygte-info.dk/info/BatteryLowVoltage UK.html

I have thrown out some LiIon batteries used to test power bank without low voltage cut-out

Those values you extracted from those old Sony and Panasonic handbooks will probably suffice for hobbyist use.

They are very old documents (and not intended for this purpose), but at least being ancient means they will apply to older cells like laptop pulls.

Readers interested in more recent information can find that by searching on related buzzwords, e.g. near zero volt storage for Lithium-ion. Due to recent Li-ion transportation restrictions there has been much recent research on ways to safely store Li-ion cells at near zero voltage because this greatly increases safety (e.g. it increases thermal runaway threshold temperature, greatly decreases amount of gas production, and eliminates all toxic gases, etc). Many of these recent papers link to the (scarce) earlier literature on overdischarge topics, and give brief overviews.