EEVblog® Electronics Community Forum
Electronics => Beginners => Topic started by: ME on June 29, 2026, 06:08:52 am
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I am going thru some cells and testing them using my litakala engineer Lii-500
I have a samsung INR 18650s-2500mah , its an old cell , in my tester doing a normal test it reads ir as82mohm and with a capacity of 3751 mah!, any ideas what is going on?
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Probably the cell is so damaged, that it has a lot of self discharge. In some modes this chargers measure the charge capacity, not the discharge capacity. So the current is likely not stored in the cell, but used to heat it up, or damage the internals, then the capacity looks a lot bigger.
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That makes sense, time to bin it me thinks.
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You could monitor the voltage for a few days (weeks) to see how much the voltage drops.
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This is a good motivation to build a hobbyist project: a battery discharge tester. As tszaboo said, the charger just told you how much energy it pumped into the battery. If we pump water into a leaky 10 litre bucket, we can easily measure we poured 20 litres into it before water hit the brim. But then we may be lucky to get 5 litres out of it.
With a discharge tester, charge the battery full. Let it rest for a day. Then discharge it at 100–500 mA,(1) until it hits 2.8 V.(2) Multiply current by time — that’s a good estimate of how much the battery can hold. In general that one day delay shouldn’t be needed, or be at most a few minutes. But that applies to healthy batteries. If it’s old, self-dicharge may eat a lot of energy in that day and give a clear indication the battery is dead. While in a shorter cycle it may appear to hold a lot of charge.
BTW, may you give some meaningful titles to your threads? You’re here for long enough to know this, but many of them are completely obscure. Thanks. 👍
(1) 0.1C to 1C is the range of currents at which batteries have their capacity specified (realisitcally). 100–500 mA is on the lower end, but I also expect 3 A discharge is not the best choice for building one’s first project of this kind.
(2) The safety zone for voltages is lower than that, but typically curves are given to 2.8–3.0 V. After that they fall sharply down and only a fraction of stored energy remains in that range. Do not discharge below 2.5–2.6 V, ever.
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This is a good motivation to build a hobbyist project: a battery discharge tester. As tszaboo said, the charger just told you how much energy it pumped into the battery. If we pump water into a leaky 10 litre bucket, we can easily measure we poured 20 litres into it before water hit the brim. But then we may be lucky to get 5 litres out of it.
With a discharge tester, charge the battery full. Let it rest for a day. Then discharge it at 100–500 mA,(1) until it hits 2.8 V.(2) Multiply current by time — that’s a good estimate of how much the battery can hold. In general that one day delay shouldn’t be needed, or be at most a few minutes. But that applies to healthy batteries. If it’s old, self-dicharge may eat a lot of energy in that day and give a clear indication the battery is dead. While in a shorter cycle it may appear to hold a lot of charge.
BTW, may you give some meaningful titles to your threads? You’re here for long enough to know this, but many of them are completely obscure. Thanks. 👍
(1) 0.1C to 1C is the range of currents at which batteries have their capacity specified (realisitcally). 100–500 mA is on the lower end, but I also expect 3 A discharge is not the best choice for building one’s first project of this kind.
(2) The safety zone for voltages is lower than that, but typically curves are given to 2.8–3.0 V. After that they fall sharply down and only a fraction of stored energy remains in that range. Do not discharge below 2.5–2.6 V, ever.
I have one of these Litokaala testers, and it has more than one mode of measurement.
In one mode, it measures the charge capacity, in another mode it's the discharge capacity.
But yes, this is a nice and easy DIY project, and you can learn a lot from it. It can be as simple as a relay an aruduino and a 10 Ohm resistor, or as complicated as an SMU.
I've seen battery testers, that were a 100KOhm resistor and some steel springs. Very reputable manufacturers run tests that lasted years with such a simple device. Some guy waled there every monday and measured the battery for years.
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I am going thru some cells and testing them using my litakala engineer Lii-500
I have a samsung INR 18650s-2500mah , its an old cell , in my tester doing a normal test it reads ir as82mohm and with a capacity of 3751 mah!, any ideas what is going on?
But you know this charger has three operating modes: charging, refreshing, and "testing." Use the latter. This mode will charge, discharge, and recharge, compare whether the previous charge value is greater or less than the last charge. If it is greater, it will test discharge again, and continue this until the next charge shows a value less than the last. Then it will end the "refreshing" loop and display the value from the last preceding discharge. The internal resistance value of this charger is purely a "marketing feature," forget about it. Inserting the same cell into the same cell ten times will show absurdly random values.
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I am going thru some cells and testing them using my litakala engineer Lii-500
I have a samsung INR 18650s-2500mah , its an old cell , in my tester doing a normal test it reads ir as82mohm and with a capacity of 3751 mah!, any ideas what is going on?
But you know this charger has three operating modes: charging, refreshing, and "testing." Use the latter. This mode will charge, discharge, and recharge, compare whether the previous charge value is greater or less than the last charge. If it is greater, it will test discharge again, and continue this until the next charge shows a value less than the last. Then it will end the "refreshing" loop and display the value from the last preceding discharge. The internal resistance value of this charger is purely a "marketing feature," forget about it. Inserting the same cell into the same cell ten times will show absurdly random values.
Nah, if you are unsure of a battery cell, bring it to a recycling center to dispose of it.
This can be after just on over-discharge. Don't try to resurrect a Li-Ion cell like a NiMH.
An 18650 is worth 2 EUR, and the house that you burn down is a lot more.
They grew dendrites, and it can go short circuit in a moments notice. It can dump it's entire energy in just 1 minutes, and the short circuit power can be hundreds of watts.
Just dispose of it safely and buy a new one.
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https://www.lygte-info.dk/ (https://www.lygte-info.dk/)
Maybe less scaremongering and more knowledge.
HKJ hasn't even burned down his test stand yet, and he's already "sliced" dozens of "those dangerous and explosive hand grenades."
"Prismatic cells" are more dangerous, but they are still used in practical applications. If someone is unlucky, a brick will fall on their head in a wooden church, three times.
https://lygte-info.dk/info/BatteryLowVoltage%20UK.html (https://lygte-info.dk/info/BatteryLowVoltage%20UK.html)
This charger will not charge if the voltage at the terminals is between 2 and 2.5 volts. This is a hardware protection. This charger will not charge if it detects excessive cell temperature (50°C), which is a hardware protection. Since the charger started charging and didn't shut down during the process, and since the cell removed from the charger "maintained the voltage at the appropriate level after 24 hours," meaning it didn't self-discharge excessively, what evidence do you base your claim that this cell is at risk of self-explosion?
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https://www.lygte-info.dk/ (https://www.lygte-info.dk/)
Maybe less scaremongering and more knowledge.
HKJ hasn't even burned down his test stand yet, and he's already "sliced" dozens of "those dangerous and explosive hand grenades."
"Prismatic cells" are more dangerous, but they are still used in practical applications. If someone is unlucky, a brick will fall on their head in a wooden church, three times.
https://lygte-info.dk/info/BatteryLowVoltage%20UK.html (https://lygte-info.dk/info/BatteryLowVoltage%20UK.html)
This charger will not charge if the voltage at the terminals is between 2 and 2.5 volts. This is a hardware protection. This charger will not charge if it detects excessive cell temperature (50°C), which is a hardware protection. Since the charger started charging and didn't shut down during the process, and since the cell removed from the charger "maintained the voltage at the appropriate level after 24 hours," meaning it didn't self-discharge excessively, what evidence do you base your claim that this cell is at risk of self-explosion?
I told you. Dendrites.
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+1
Get rid of cells with unusual readings especially the ones with a very lo charge efficiency
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I am going thru some cells and testing them using my litakala engineer Lii-500
I have a samsung INR 18650s-2500mah , its an old cell , in my tester doing a normal test it reads ir as82mohm and with a capacity of 3751 mah!, any ideas what is going on?
What is the exact model printed on the cell?
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It has " INR18650S-2500mah 3.6v
9.0WH uj11052emx 221098 writen on it ok.
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So its a no name Chinese copy probably this one https://ancoo-battery.com/en/product/18650-MP2500mAh.html
INR18650S Cell Specification:
Model: INR18650S-2500mAh
Rated capacity: 2500mAh
Actual capacity: 2580mAh
Discharge current: 7.5A, 3C
Rated Capacity range: 2520mAh~2580mAh
Voltage:3.639V~3.644V
Inner Resistance: 15mΩ~20mΩ
Diameter:18.2mm+/-0.2mm
Height:65.2mm+/-0.2mm
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I am going thru some cells and testing them using my litakala engineer Lii-500
I have a samsung INR 18650s-2500mah , its an old cell , in my tester doing a normal test it reads ir as82mohm and with a capacity of 3751 mah!, any ideas what is going on?
Capacity is measured as the amount of charge the battery can deliver to a load during a full discharge (typically from 4.2 V down to cutoff), not what it takes in during charging.
For an old 2500 mAh 18650 cell, getting 3750 mAh is essentially impossible — it already exceeds even the nominal capacity of new cells in that class.
Most likely this points to a measurement or tester issue.
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The self-discharge will be very obvious if the cell has developed high-resistance leakage.
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--------------------------------meaning it didn't self-discharge excessively, what evidence do you base your claim that this cell is at risk of self-explosion?
I told you. Dendrites.
Any research data, not just dry rhetoric?
Because I can say, "I said stalactites and stalagmites."
I know that elemental lithium dendrites can "form" under specific operating conditions (charging with high currents at very low temperatures), but this is more of a problem with electric scooters, not with home-used flashlight batteries. This is something that Norwegians, Swedes, Danes, or even Americans in Alaska might be concerned about, as well as Russians in deep Siberia – although they prefer reindeer for reliable transport there.
https://belltestchamber.com/lithium-ion-battery-low-temperature-high-rate-cycling-test.html
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--------------------------------meaning it didn't self-discharge excessively, what evidence do you base your claim that this cell is at risk of self-explosion?
I told you. Dendrites.
Any research data, not just dry rhetoric?
Because I can say, "I said stalactites and stalagmites."
I know that elemental lithium dendrites can "form" under specific operating conditions (charging with high currents at very low temperatures), but this is more of a problem with electric scooters, not with home-used flashlight batteries. This is something that Norwegians, Swedes, Danes, or even Americans in Alaska might be concerned about, as well as Russians in deep Siberia – although they prefer reindeer for reliable transport there.
https://belltestchamber.com/lithium-ion-battery-low-temperature-high-rate-cycling-test.html (https://belltestchamber.com/lithium-ion-battery-low-temperature-high-rate-cycling-test.html)
Is google blocked in Poland?
https://www.retron.world/en/blog/detail/batteries-deep-discharge-recovery/ (https://www.retron.world/en/blog/detail/batteries-deep-discharge-recovery/)
Why you should not recharge deeply discharged batteries.
A deeply discharged lithium-ion battery is usually permanently damaged so that it will no longer achieve the capacity or output of a new battery. It is therefore usually not worth revitalising a deeply discharged battery anyway. Recharging is also associated with risks:
If a deeply discharged lithium-ion battery is recharged, so-called dendrites can form from lithium or other electrode materials such as copper. These can be imagined as a small metallic spur that continues to grow with each charging process and can also pierce the membrane between the electrodes. If it reaches the other electrode, a short circuit occurs, which can lead to thermal runaway. This means that the battery spits fire under high pressure or even explodes.
https://www.batteryuniversity.com/article/bu-802b-what-does-elevated-self-discharge-do/
(https://www.batteryuniversity.com/article/bu-802b-what-does-elevated-self-discharge-do/)
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.
Regular charge and discharge causes an unwanted deposit of lithium metal on the anode (negative electrode) of Li-ion, resulting in capacity loss through a depletion of the lithium inventory and the possibility of creating an internal short circuit. An internal short is often preceded with elevated self-discharge, a field that needs further research to learn what levels of self-discharge would pose a hazard that can lead to a thermal runaway. Unwanted lithium deposition also increases the internal resistance that reduces loading capability.
It's a very bad idea to risk all this for a cell, when you can just buy a new one for 2 EUR.
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That makes sense, time to bin it me thinks.
Yep. These cells have a finite life, even if you have a good charger which doesn't overcharge them and you don't over discharge them. You can expect the mAh you put in during charge to be greater than the mAh out during discharge, but not to the extent of 3,751mAh against a (nominal) 2,500mAh. That indicates something wrong.
If it started out as a genuine 2,500 mAh cell, after many charge-discharge cycles and the passing of years, it will have degraded.
For what they cost, just buy another one. Choose a leading brand; LG, Samsung, Panasonic. They are not that much more expensive. Avoid the cheapies, which have probably been recovered from laptop packs and have ridiculous mAh capacities printed on them. Most of those have an actual capacity of less than 1,000 mAh.
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--------------------------------meaning it didn't self-discharge excessively, what evidence do you base your claim that this cell is at risk of self-explosion?
I told you. Dendrites.
Any research data, not just dry rhetoric?
Because I can say, "I said stalactites and stalagmites."
I know that elemental lithium dendrites can "form" under specific operating conditions (charging with high currents at very low temperatures), but this is more of a problem with electric scooters, not with home-used flashlight batteries. This is something that Norwegians, Swedes, Danes, or even Americans in Alaska might be concerned about, as well as Russians in deep Siberia – although they prefer reindeer for reliable transport there.
https://belltestchamber.com/lithium-ion-battery-low-temperature-high-rate-cycling-test.html (https://belltestchamber.com/lithium-ion-battery-low-temperature-high-rate-cycling-test.html)
Is google blocked in Poland?
https://www.retron.world/en/blog/detail/batteries-deep-discharge-recovery/ (https://www.retron.world/en/blog/detail/batteries-deep-discharge-recovery/)
Why you should not recharge deeply discharged batteries.
A deeply discharged lithium-ion battery is usually permanently damaged so that it will no longer achieve the capacity or output of a new battery. It is therefore usually not worth revitalising a deeply discharged battery anyway. Recharging is also associated with risks:
If a deeply discharged lithium-ion battery is recharged, so-called dendrites can form from lithium or other electrode materials such as copper. These can be imagined as a small metallic spur that continues to grow with each charging process and can also pierce the membrane between the electrodes. If it reaches the other electrode, a short circuit occurs, which can lead to thermal runaway. This means that the battery spits fire under high pressure or even explodes.
https://www.batteryuniversity.com/article/bu-802b-what-does-elevated-self-discharge-do/
(https://www.batteryuniversity.com/article/bu-802b-what-does-elevated-self-discharge-do/)
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.
Regular charge and discharge causes an unwanted deposit of lithium metal on the anode (negative electrode) of Li-ion, resulting in capacity loss through a depletion of the lithium inventory and the possibility of creating an internal short circuit. An internal short is often preceded with elevated self-discharge, a field that needs further research to learn what levels of self-discharge would pose a hazard that can lead to a thermal runaway. Unwanted lithium deposition also increases the internal resistance that reduces loading capability.
It's a very bad idea to risk all this for a cell, when you can just buy a new one for 2 EUR.
https://www.youtube.com/watch?v=-Y23nfAOiXQ (https://www.youtube.com/watch?v=-Y23nfAOiXQ)
I asked for "research," not a link to a storefront or a link to a pseudo-university website so overwhelmed with data processing consents and the sale of that data "to the world." I wasted 20 minutes blocking over 500 cookie consents, not to mention the fact that my laptop's processor overheated from trying to block ads.
he store's website recommendations, "to use a battery pack" or "to raise 0V cells by connecting them in parallel with a charged cell," are absurd. If someone wants to burn down their house, they should use the in-depth knowledge from there. I'll stick to the academic sources I'm familiar with.
EOT.