# When do you know your Li-Ion battery is at end of life cycles?



## theFLASH12 (Sep 1, 2012)

So I've seen that a big percentage of multi-cell LED Flashlights use such batteries such as 18650's or 26650's or even rechargeable CR123's. These batteries are often advertised as having 500 cycles or more of charging cycles capability. Without high dollar analyzing equipment how is one to know that a cell cannot be charged anymore (or preferably, right before then)? By the mere fact that it won't charge anymore? 

After reading some of the horror stories of flashlight explosions in this forum, I'm spending a little more time in monitoring possible anomalies with my Li-ion batteries during charging and measuring voltages (handheld DMM) before I install them in my LED Flashlights.

FYI, I have a SoShine SC-S1 charger that I believe it's CV/CC charging, and it has LED monitoring of individual charge bays for batteries: Charging, 80-90% charged, 90-100% charged, reverse polarity detection.


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## berry580 (Sep 1, 2012)

From my understanding, li-ion battery, unless abused e.g. Extreme temperature exposures, overdischarged, overcharged, etc. It's not likely to blow up.

If there's any reason to believe it's near the end of its like, dispose immediately. Preferably in one of those mobile phone recycle box.

Please correct me if i'm wrong as my knowledge is limited.


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## JohnnyBravo (Sep 1, 2012)

Welcome to CPF theFLASH12! What I do is date all of my rechargeables with a Sharpie or labelmaker label. That way I can somewhat estimate how many charge cycles I do for my batteries on average, so I can recycle them a little before the 500th charge, or 5 yrs from date of purchase - whichever happens first...


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## 45/70 (Sep 2, 2012)

Hi FLASH, and welcome to CPF!:thumbsup: You really at the minimum, need a means to measure cell voltage, such as a DMM if you're going to be using Li-Ion cells. This will make it much easier to determine cell health, as well as add a margin of safety to your Li-Ion use.

Without an analyzer, or running runtime test etc, the easiest way to tell that a Li-Ion cell is nearing it's EOL, is that it will not hold a charge well, will not perform as well as it used to, and will get noticeably warmer when charging.

With a means to measure cell voltage, you can tell if a cell is holding charge well, or not by measuring the cell's voltage after charging. Newer LiCo/ICR, or LiMn/IMR cells will typically charge up to 4.18-4.20 Volts when charged with a proper CC/CV charger. Newer cells will also stay at this voltage for quite some time. Older cells will loose some voltage soon after charging. If cell voltage drops to ~4.10 Volts after charging to 4.18-4.20 Volts, after a day or so, the cell is well on it's way towards EOL. In general, cells that drop to 4.00 Volts, are considered at EOL and should be replaced. Also, it is generally accepted that Li-Ion cells should be disposed of /recycled when the charged capacity has dropped to 80% of the original capacity of the cell.



berry580 said:


> From my understanding, li-ion battery, unless abused e.g. Extreme temperature exposures, overdischarged, overcharged, etc. It's not likely to blow up.



Usually, when a Li-Ion cell is used up, it just doesn't work as well. It doesn't hold voltage under load as well as it did when new, exhibits a higher rate of self discharge, and warms up when charging (this is an indication of high internal resistance, which is associated with cell degradation). So, in most cases the cell simply lacks the performance it once had. 

The problem with old worn out Li-Ion cells is that the chemical components within the cell tend to become unstable. Add to this the fact that these cells get much warmer when charging, and you may have a problem.

All Li-Ion cells use a volatile electrolyte. They also have the ability to create oxygen within the cell. Add heat created during charging (or discharging, as well) of a cell which has a high internal resistance, and you increase the chances of a "vent with flame" incident occurring.

As I said though, normally a used up cell simply doesn't perform as well. Just the same, there still exits the possibility of running into more "advanced" problems with old/under performing Li-Ion cells. This applies especially to LiCo/ICR cells, somewhat less with LiMn/IMR, and LiFe/IFR (LiFePO4​) cells are the least likely of the three most common Li-Ion cell chemistries we use on our lights, to run into problems.

Dave


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## HotWire (Sep 2, 2012)

When my li ion cells begin to lose their charge or have poor performance, I recycle them. No use asking for trouble! You'll know when the flashlight should light, but does not.


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## moldyoldy (Sep 2, 2012)

45/70 gave good advice on measuring the cell voltage after charge and before usage. 

Another factor which has been mentioned more specifically in other threads is the temp of the cell during charge. You should routinely check (finger/palm feel) the temp of the Li-xxx cells during charge. Calibrate your fingers as to what "normal" and "hot" represents by acquiring some data history. Assuming common chargers and reasonable charge rates, any cell that becomes hot should be disposed/recycled. I recently had a 10440 on a 0.3A charge rate that uncommonly became hot when the other 3x 10440 cells that were previously charged did not become hot, more lukewarm. End of any discussion for that cell.


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## roadkill1109 (Sep 2, 2012)

Hello! Well, if you drain it to less than 1 volt, you'd kill the rechargeable li-ion battery. (I've already killed two unprotected RCR123's DOH!) I guess the only way to find out if a battery's going bad is that your light is starting to display noticeably decreased runtime. Also, it seems to charge faster than the rest. Kinda like an easy come, easy go type of deal. Haha!


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## theFLASH12 (Sep 3, 2012)

Thanks everyone for the warm welcome, and awesome Technical advice (especially 45/70, for the concise technical info I needed....with me being a newbie). I do measure my cells from time to time, now I know what to look for and trend to try and avoid problems.


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## RCS1300 (Sep 3, 2012)

*How will I know that my 18650s need replacement?*

I purchase some Redilast 2600 and AW 2600 18650 batteries in December 2010 along with a Pila charger. The Redilasts have seen the most use and have been charged about 20 times. The AW's have been charged about 8 times. 

Is there a time period to note before I replace them or is it the number of charging cycles or a combination of both? How will I know when to replace these batteries?


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## roadkill1109 (Sep 3, 2012)

*Re: How will I know that my 18650s need replacement?*

Based on online specs and descriptions, its good for about 500 recharge cycles. 

Normally if they drop in voltage quickly even when not in use, the battery's might be going bad. 20's not long enough, even if it is over a two-year period. You might have a defective cell.


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## RCS1300 (Sep 3, 2012)

*Re: How will I know that my 18650s need replacement?*

Below is what I read on Wiki. The comment suggests that since I keep my cells fully charged and ready in flashlights that they lose about 20 percent of their capacity per year. That means I should probably replace them at the end of year 3. That would be December 2013 for me. Any thoughts?

"A Standard (Cobalt) Li-ion cell that is full most of the time at 25 °C(77 °F) irreversibly loses approximately 20% capacity per year. Poor ventilation may increase temperatures, further shortening battery life. Loss rates vary by temperature: 6% loss at 0 °C(32 °F), 20% at 25 °C(77 °F), and 35% at 40 °C(104 °F). When stored at 40%–60% charge level, the capacity loss is reduced to 2%, 4%, and 15%, respectively.[50]​ In contrast, the calendar life ofLiFePO4​ cells is not affected by being kept at a high state of charge.[51]"​


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## HighlanderNorth (Sep 3, 2012)

moldyoldy said:


> 45/70 gave good advice on measuring the cell voltage after charge and before usage.
> 
> Another factor which has been mentioned more specifically in other threads is the temp of the cell during charge. You should routinely check (finger/palm feel) the temp of the Li-xxx cells during charge. Calibrate your fingers as to what "normal" and "hot" represents by acquiring some data history. Assuming common chargers and reasonable charge rates, any cell that becomes hot should be disposed/recycled. I recently had a 10440 on a 0.3A charge rate that uncommonly became hot when the other 3x 10440 cells that were previously charged did not become hot, more lukewarm. End of any discussion for that cell.





What do you use 10440's for?


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## 45/70 (Sep 3, 2012)

*Re: How will I know that my 18650s need replacement?*

A similar question to this was asked a couple days ago. There are certain signs that appear when Li-Ion cells are at, or near EOL. A means of measuring cell voltage is a big help when attempting to determine when it's time to retire Li-Ion cells. As to what causes Li-Ion cells to wear, it's a combination of age, number of cycles, depth of discharge each cycle, average current load under discharge, storage and use conditions, etc.

Dave


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## moldyoldy (Sep 4, 2012)

HighlanderNorth said:


> What do you use 10440's for?



I have used 10440's in my various copies of the Fenix LD01 for a long time, for far more than a year, probably since the LD01 was on the market. As long as I use it for brief but magnificent bursts of light a few minutes at a time and primarily on medium, none of which allows the light to get hot, no problem. An acquaintance has been using the same LD01 for almost a year. I lost an L0P after maybe a year on 10440s. also an E05 in a couple minutes! But so far I have enjoyed the over-engineering in the LD01 w/o failures. Otherwise none of the 1x AAA-based lights provide enough lumens for these old eyes... :thinking:


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## roadkill1109 (Sep 4, 2012)

one other light that is noteworthy is the old iTP A3 Upgraded. It blasts 200+ lumens using a 10440 and has good runtimes when run in medium (which is the more used mode).


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## SuLyMaN (Sep 4, 2012)

Hum if lion cells can be potentially so dangerous, it would make sense to charge it in my garage in the 'semi-open'?


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## moldyoldy (Sep 5, 2012)

SuLyMaN said:


> Hum if lion cells can be potentially so dangerous, it would make sense to charge it in my garage in the 'semi-open'?



easy question - long answer:

Based on my limited Li-Ion experience, quality Li-Ion cells with protection circuits are not really that dangerous as long as the user is paying attention to the usage and charging processes, each and every time. Li-Ion cells should not be treated as a higher-energy form of NiMH cells! 

A digression: NiMh cells have evolved to the point that the user can use the cells until the light is obviously dimming, then drop them in to a modern smart charger and walk away. Sometime later the user discovers that the charging process ended and the cells might be removed for use/storage. That "casualness" is not advised for use and charging of LiIon cells. I have had a few cases of higher-priced Ni-MH chargers failing - meaning melting with smoke - due to component failure well past the usual bathtub curve of life expectancy - my bad! 

BTW, I consider any fast charge method for any charger to be dangerous and which requires close monitoring during charge, if used. Specifically I avoid the highest current settings of any charger until I learn more about the charger from actual use. I find it curious that my 2 copies of the BC-900 have been reliable, but I use them only to the BC-700 levels (which I also have). My point is that the BC-900(1000) have a poor reputation whereas the BC-700 has a reasonable reputation.

Back on topic:

The voltage of Li-Ion cells should be periodically monitored during each discharge cycle, at least until the characteristics of use in that particular light are known. Then when inserted in to a quality charger, the charging process again needs to be periodically monitored.

What does Li-Ion cell monitoring constitute? Check the discharge voltage level with a digital voltmeter! It is highly preferable to remove the cells from use for charging before the voltage trip level of the protection circuit is reached and the circuit is broken leaving the user suddenly in the dark. During charging in a quality charger, the voltage and temp of the cell is monitored. A temp check can be accomplished by a hand/palm touch of the cell and charger during charging. Preferably check the voltage at the end of every charge. Pay attention to when the Li-Ion cell has nominally completed a charge cycle and remove those cell(s). 

In no case should any charger for any chemistry be in contact or "flame range" of an easily flammable material such as paper or cloth!!! That is not a discussion point! Even in the military (back then) our Ni-Cd "pocket" cells were contained w/in metal boxes.

FWIW, to my recollection, I have had no problems with Li-Ion cells other than aging. I recycled many Li-Ion cells because of lowered capacity or lowered voltage during use as well as excessive heating during charge. I have had problems with Lithium (CR123a) cells which too often lost their capacity far in advance of any date code. 

What does "quality" mean for a charger and Li-Ion cell? Education is the key. There are many charger and cell tests available on CPF. Low $$ usually means low quality! The source needs to be considered in any purchase decision.


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