Old LiIon Battery voltage settling/drop after full charge

[kosPap]

It has been a while, so I do not remember any.
If we are to measure an old battery's voltage after charging, we are to see voltage settling lower than 4.2 (nominal) after some time.
the amount of voltage drop and the time it took to go there, is considred an (aproxiamte) sign of old age and wear. Doesn't it?

i.e I have read somewhere that the resting voltage droping to 4.15 is such a sign.

If so, what woudl be a practical guideline

PS (being more specific I had a friend ask me why his drill battery shows less than full when freshly inserted to the drill)

 

[Stress_Test]

I also have noticed the falling-voltage behavior on old or degraded li-ion batteries. I've got an older Xtar charger that keeps displaying the battery voltage after charging has stopped. On some older cells, the voltage will fall over a couple hour's time from 4.20 to 4.15 or so.

I've got some Nitecore cells that are pretty bad that will fall to about 4.10 after only 4 or 5 hours.

I've had camera batteries do the same thing; either they don't get to 4.20 at all, or that rapidly fall back down to ~4.10 range after charging.

New, known good cells will hit 4.20 or 4.19 upon charging, and hold that level for weeks without dropping.

Sometimes you can get new cells that are defective somehow; I had a new Canon battery that never would charge up to full capacity. Off the charger and into the camera it still would only show about 60 or 70 percent full.

I don't have technical rationale, but my own view is that any of my flashlight cells that are dropping below 4.15 in only a few weeks are suspect and not to be fully trusted for any critical use (they may also not put out the full current they should).

 

[chillinn]

New, known good cells will hit 4.20 or 4.19 upon charging, and hold that level for weeks without dropping.

This is something I have never, ever seen. Every li-ion I have ever seen terminates at 4.20V, but after charging (after a day or longer) rest around 4.12V. Since 2014, and I not seen anything but this.

 

[sbj]

.....the amount of voltage drop and the time it took to go there, is considred an (aproxiamte) sign of old age and wear. Doesn't it?

i.e I have read somewhere that the resting voltage droping to 4.15 is such a sign.

If so, what woudl be a practical guideline......

Yes, the increased voltage drop compared to when it was new, can be seen as an indication of an aged battery. Doubling the voltage drop in the same time means about twice the internal resistance of the battery. The prerequisite for this is, that the termination current at the end of charging was just as high, as when the battery was new.
If the same charger and charging program is used, then that is probably the case.

The voltage of the drill battery will drop more under load. The maximum torque decreases and the battery gets hot faster.

 

[sbj]

However, this lower open-circuit voltage should only serve as an indicator of the declining performance of a battery. You get more precise assessment criteria if you have the opportunity to measure the internal resistance of the battery.
You should do this already when it is new and note the battery temperature.

Then you will later have a reference value to be able to assess the condition well.

Of course, chargers that can reasonably measure the direct current internal resistance or pure internal resistance measuring devices for batteries are relatively expensive.

 

[dragosios]

Just take into account that not-so-expensive chargers do measure with a degree of accuracy and it better be an error showing a higher voltage on charger than it is at the cell terminals.
If you want very high precision and play with numbers, try a lab power supply with enough resolution, or even a multimeter with 3+ digits, the more the better (but more expensive). These power supplies can do a 4 wire measurement and compensate accordingly, but we are talking about prices maybe even 100x more than an average charger.

 

[aznsx]

It has been a while, so I do not remember any.
If we are to measure an old battery's voltage after charging, we are to see voltage settling lower than 4.2 (nominal) after some time.
the amount of voltage drop and the time it took to go there, is considred an (aproxiamte) sign of old age and wear. Doesn't it?

i.e I have read somewhere that the resting voltage droping to 4.15 is such a sign.

If so, what woudl be a practical guideline

PS (being more specific I had a friend ask me why his drill battery shows less than full when freshly inserted to the drill)

I agree in principle with most of what's been said in this thread so far, but with one exception:

I believe your threshold of concern is set too high. I'm no batt expert, but just from my own limited experience and observation, I'd say your threshold is probably too high by something in the range of ~ .05-.15 V. When I see something in the 4.00-4.10 range in the short term, that's where I begin to suspect some degradation has occurred that might warrant an IR / capacity re-test. Most of my cells (including newer ones) will settle from 4.20 to 4.15V in a relatively short time (from a few hours to a few days), then usually stabilize there for some longer time period, and I consider 4.15V to be a 'nominal' short-term settling value, and not of concern.

I realize we're talking about small differences here, but they do matter and are indicative of cell health, and one's 'meter' needs to be sufficiently good to resolve those differences, although it doesn't require anything 'high end'. The only reason I add that comment is because some really scrape the bottom when shopping for a meter and buy the cheapest thing they can find, there's a lot of 'junk' on the market in the current times (Edit: same with flashlights), and some of those are likely not a reliable indicator when making decisions based on tens of millivolts.

 

[kosPap]

thanks all for replying so far....
question is: how low would a battery, with 20% or 40% of its capacity lost, show (resting voltage)?

Here are some voltages measured 20.11V for a 20V power tool battery
10.96, 11.78V for a 12V power tool battery.

 

[aznsx]

thanks all for replying so far....
question is: how low would a battery, with 20% or 40% of its capacity lost, show (resting voltage)?

Here are some voltages measured 20.11V for a 20V power tool battery
10.96, 11.78V for a 12V power tool battery.

I don't have a good answer to that. I started to mention this earlier, but one thing I don't have a good feel for is the relationship between specific capacity loss, and lower resting voltages after settling following charging. I imagine such a relationship exists and can be approximated, but I lack the experience / data to do so. Someone else with more experience / observations may have that answer.

 

[kosPap]

hypothesis.....

assuming that resting voltage is 3.8......
and in practical terms any battery that is used a while and measures 3.8 has about 40% capacity left (CPF rue of thumb)
could we suppose that the cell in question has lost 60% of its capacity?

reference:

Charge voltage experiments with lithium ion batteries showing how capacity varies with charge voltage and higher cycle live with lower charge voltage

Lithium battery charging data (voltage versus capacity) for equipment designers from PowerStream

www.powerstream.com

 

[sbj]

3.8V after a full charge?
I think you are confusing something now.

If the cell of a LiIo battery shows an open circuit voltage of 3.8V, it has been discharged to about 40% state of charge. That's why you can still charge it back to 4.20V.

A battery that drops to 3.8V open-circuit voltage after a standard charge would have been useless already for a long time!
---------
As an aging criterion, I would not focus so much on the loss of capacity, but primarily on the increasing internal resistance. This is also mainly responsible for the fact that you can actually get less capacity from an aged battery.

For applications that require very little power, such aged batteries can still be used.

 

[Sjvalleydave]

hypothesis.....

assuming that resting voltage is 3.8......
and in practical terms any battery that is used a while and measures 3.8 has about 40% capacity left (CPF rue of thumb)
could we suppose that the cell in question has lost 60% of its capacity?

reference:
[URunfurl="true"]https://www.powerstream.com/lithium-ion-charge-voltage.htm[/URL]

I think you are close, but I'd probably flip your %. Most Li ion chargers will charge to 4.1-4.15V. Nominal voltage is almost always 3.6-3.7V and lo voltage cutoff is 2.5V for most manufacturer's. A few use 3.0 and a good cell will pull all the way down...so you've got 1.1V left down to 2.5, and you came down .6V

 

[dragosios]

Cheap multimeters can be specified as 3% plus last digit, which can usually be more than 0.0x volts you are looking to measure with precision.
If you want to go that deep prepare to spend some money on calibrated meters.
E.g. ANENG AN8008 which is a popular cheap one has specs of 0.5%+3 digits. That translates into + or minus 0.02v error, and if the last digit adds to that even 0.03V error. Which makes your 4.20V be more like 4.17 all the way up to 4.23v.
Add to all of that thermal erors (altough not huge).

 

[Sjvalleydave]

What I do is first measure the IR of the cells. If newer good ones are at 10-16 milli ohms, and you seeing 35, 40 mohms it's a tired old battery. Then I'll double check, I'll bring it up to 4.1v then draw it down at 1A and look at 2 things. How long it took and how many mA's I got out of it. 35 minutes and 500 mA vs a real good one at 2 hours and 1800mA.

 

[dragosios]

At 35-40mOhms is still usable if current demands are not that high. I use ones in the 80's in low current requirements.

 

[Sjvalleydave]

Cheap multimeters can be specified as 3% plus last digit, which can usually be more than 0.0x volts you are looking to measure with precision.
If you want to go that deep prepare to spend some money on calibrated meters.
E.g. ANENG AN8008 which is a popular cheap one has specs of 0.5%+3 digits. That translates into + or minus 0.02v error, and if the last digit adds to that even 0.03V error. Which makes your 4.20V be more like 4.17 all the way up to 4.23v.
Add to all of that thermal erors (altough not huge).

I agree...my nice meter goes out as far as 1.484v

 

[Sjvalleydave]

hypothesis.....

assuming that resting voltage is 3.8......
and in practical terms any battery that is used a while and measures 3.8 has about 40% capacity left (CPF rue of thumb)
could we suppose that the cell in question has lost 60% of its capacity?

reference:

Charge voltage experiments with lithium ion batteries showing how capacity varies with charge voltage and higher cycle live with lower charge voltage

Lithium battery charging data (voltage versus capacity) for equipment designers from PowerStream

www.powerstream.com

Good article in the Power Stream site. Also excellent article about dual pulse Capacitor Discharge spot welders...

 

[Dave_H]

From recovering 18650s from battery packs, I check post-charge voltage over several days, have no special charge/condition/load-test capability. Results vary from those which hold up OC voltage 4.15-4.20v over weeks to months; others may fall to 4.0v or below in days (or hours). Latter is attributed to increased internal leakage, and they are put aside for proper disposal. I'll do some sort of capacity test by running cell down in a small single-cell light.



Dave

 

[dragosios]

@Dave_H would be interesting to see how the ones with high discarge rates behave when you discharge them with a high (enough) current and recharge.
Not full discarcharge, just a few pulses.
I am curious about what happens and I have no such cell yet.

 

[NiOOH]

The voltage drop of a charged LiIon cell depends upon two things:
1. Cell quality and age.
2. How it has been charged.
Old cells or ones that have been dropped or shortened may develop internal micro shorts that increases their self discharge. You may expect such cells to drop their OCV below 4.10 V for days or even hours after full charge.
Charging is also important. If the cell has been charged to below 4.20 V, or the end of charge current is high (higher than 10 % of the CC-phase current), the OCV will be low.
Also, make sure that you use a good quality DMM for measuring OCV. For work on cells and batteries, I'd recommend something with at least 5000 count display and accuracy of 0.5 % or better. It is a good idea to check it from time to time against a reference voltage source or other well calibrated equipment.
A healthy LiIon cell that has been properly charged should maintain an OCV over 4.10 V for days or weeks at room temperature.