# How can this be? Li-Ion brought back from 0.1v to full power and working strong?



## matrixshaman (May 3, 2007)

I've learned a fair amount here recently about Li-Ion rechargeable batteries. Much thanks to Silverfox and others. So I dug out a portable ham radio transceiver I bought a few years ago and saw it had a Lithium-Ion battery pack which is 7.2 volt. I assume two 3.6 volt batteries in it. I check the voltage with my Fluke 77 at both points on this pack and at both points it reads about 0.13 volts. So I am thinking the battery is toast - gonzo - not even worth charging. But never say never is sort of one of my motto's so I put it on the charger for several hours while I'm right near by. I just pulled it off and checked the temperature first with a digital laser thermometer. It was 83° and ambient room temperature was 72°. I check the voltage and it is 7.65 volts. Looks fully charged but is it? I turned on the transceiver after removing the charger and it worked great - scanned some and then hit the transmit button - which at 5 watts output is probably drawing at least 1 amp from the battery. I held it down a few seconds and then checked the voltage again on the battery. It read 7.62 volts so from that brief test it certainly seems so far the battery is okay. Am I missing something here? I thought you could not revive a Li-Ion battery that was that depleted and that attempting to do so would cause overheating and no chance of reaching a useable charge. Ideas? Magic battery?


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## LEDite (May 3, 2007)

Matrixshaman;

I've seen many "high quality" cells by Sanyo, Sony & Panasonic revive from that level also.

I have tested internal resistance and found it normal or slightly increased.

Capacity is usually reduced by 10% or so.

Larry Cobb


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## LuxLuthor (May 3, 2007)

Being the never ending noob that I am....how does one go about testing the internal resistance of batteries? Is it just a matter of putting the DMM on Ohms and touching POS & NEG terminals?


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## Josey (May 3, 2007)

I have a protected Pila cell that does this on a regular basis. If I discharge it too low, it pops down to about 0 volts. I guessed it has something to do with tripping a protection circuit, but I don't really know.

I measure internal resistance with an ohm meter, but the polarity has to be respected.


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## UncleFester (May 3, 2007)

LuxLuthor said:


> Being the never ending noob that I am....how does one go about testing the internal resistance of batteries? Is it just a matter of putting the DMM on Ohms and touching POS & NEG terminals?


 *ABSOLUTELY* do not do that. If there is ANY charge in the cell it could instantly take out your meter.
To measure the internal resistance of a cell, charge it and load it with a known current. Measure the terminal voltage with and without the load. Subtract the loaded voltage from the unloaded voltage. That difference in voltage will be some (hopefully) small number. 
If E is the difference voltage and
I is the (known) current and
R is the resistance you're looking for, THEN
by Ohm's law 
E= I x R or
E/I = R 
In Other Words, divide the difference voltage by the known current and that should give you the internal resistance of the cell. 
Hope this helps.


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## VidPro (May 3, 2007)

nobody ever said you could not revive a fully discharged one.
but that it gets Hurt, and hurt badly from full discharge, especially if this was a self discharge in addition to.

check the total capacity, and the self discharge of it, self discharge is a big clue that its hurt badly.

i have revived (so to speak) 10s of 18650 cells that were very low or all the way low, and the ones that were all the way low, were total trash, on charging they took WAY more power in than they output, and self discharged in less than a day.
the ones that were very low, but not all the way, were applied, fruitlessly , they were a total waste of time, eventually self discharging, heating on charge, and having little capacity.

check for the self discharge of it.

you also didnt mention the type or capacity of the cell, the brand or anything, certannly they can make a lower capacity for weight/size cell that handles deep discharge better, but mabey it would have Much more lithium in it ?, or something making the plates huger, so they dont decay away as far.

i assume from the way you indicate testing, that this a PACK, that you tested the cell items IN the pack, because most packs can be at 0 and that does not mean the cells themselves are at 0 nessisarily.

if the cell is junk, its not the first time you turned it on and run a bit of load on it after charging, you find out later.


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## SilverFox (May 3, 2007)

Hello Matrixshaman,

Let me see if I correctly understand what you discovered...

You have a 2 cell Li-Ion pack that was totally discharged. You charged it up and when the charger indicated that the charge was complete, your cells ended up charged to 3.825 volts per cell.

You went on to power up your radio and discovered that the battery held some charge and was able to power the radio, both in receive and transmit modes.

Do I have this correct?

First of all, a dead cell can accept a charge and power a load. It just is not safe to do so.

Secondly, your charger seems to be malfunctioning. There are several "issues" with charging over discharged Li-Ion cells, so the charger manufacturers have designed the chargers to reject cells when they are over discharged and terminate the charge. The charger should have thought that you were trying something "funny" and refused to charge your pack. 

Now, let's look at the cells...

If I told you that I found some old NiMh cells in the back of the drawer, check their voltage and found them at 0 volts, charged them up and found that they charged all the way up to 1.2 volts, then dropped them into a light and it turned on, what would you say about that...

While this is not the same, it is similar.

Your cells did not charge up to 4.2 volts. This is the first warning sign that something is not right. An open circuit resting voltage of 4.0 volts indicates that the cell is at around 80% of its initial capacity. If your cells do not charge up to that level, they are probably damaged.

Your cells charged up to 3.8 volts, which is around 40% capacity.

I have been running some tests on over discharged cells and the results are "interesting." The amount of damaged caused by over discharging is related to the amount of time the cell is in the discharged condition, and the quality of the cell.

Larry pointed out that premium cells often "recover," but there is some loss in capacity. The reason for the loss of capacity is that the electrolyte is corrosive and in an over discharged state, the electrolyte dissolves the copper electrode. Reducing the size of the electrode results in reduced capacity.

Yesterday I ran a test on an over discharged Li-Ion cell. The cell charged up normally, but after a full charge, it was only at just over 4 volts.

I discharged the cell at a 1C discharge rate, and the discharge curve was not uniform, but jumped around as if I had a loose connection within the cell.

The discharge capacity was less than half of the cells original capacity, so I know the cell suffered damage.

I did not want a damaged cell to cause any surprises, so I decided to totally discharge the cell down to 0.1 volts, then recycle it. The cell voltage quickly dropped, but then the cell heated up and the voltage rose back up. It got high enough to be useful in operating equipment. It then started another, somewhat normal, discharge curve and I got around another 25% of the cells capacity. The problem was that the cell temperature was rising during this discharge process. The cell temperature got up to 165 F, and the shrink wrap on the cell, shrunk.

I am not sure exactly what happened, but think it has to do with the dissolved copper trying to short out the cell. I was surprised that the cell seems to charge normally, then heated up during the discharge. I may have to monitor a charge on it to see if it is a smooth charge or if there are issues with charging as well.

Even though I can charge this cell up and use it to power a 2 amp load, the cell is not stable and should not be used. 

I understand your curiosity, but keep in mind that the electrolyte that is used in Li-Ion cells is flammable, and that damaged cells are far more likely to have problems that cause cell heating. 

I hope you understand that your battery pack is not OK, and should be replaced.

I do not recommend trying to recover over discharged Li-Ion cells. While it sometimes is possible, I feel that the risks far outweigh any benefits

Tom


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## Josey (May 3, 2007)

This is interesting. One of my favorite EDC lights runs on a Pila 150S. If the battery gets too low, the light will start to blink. If I don't catch it right away, the cell will pop down to 0 volts, or just above. But it charges up just fine and runs an Aleph II LE for a long time. I just checked it for voltage, after a small amout of use since I charged it up a couple of weeks ago. It read 4.124 volts.

As for measuring internal resistance, the regular ohm meter has worked for me as a means to confirm a bad cell. I bought a batch of Li-Ions recently and one was bad. I could tell by the resistance difference compared to my other, fully charged cells. My meter (Fluke 179) was fine with this ordeal. I could not use UncleFester's method because the cell will not run anything, nor will it charge up. I know that measuring resistance of electronics while under a load could destroy some of the electronic components, but I didn't know it could damage my meter.


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## matrixshaman (May 3, 2007)

First thanks for all the replies and help on this. A couple replies indicate that some have 'Protected' cells that go to Zero volts. That IS normal if they run past the protection voltage of around 2.7 volts - the protection circuit opens the connection to the battery preventing further discharge a you will only see Zero volts but the battery is at 2.7 volts roughly. It didn't occur to me that my battery pack might have protection as it did have some voltage on it as mentioned. 
Silverfox - I did not try to fully charge this battery pack as it indicated it was still charging and it was time for me to go to bed so I pulled it off the charger and quickly did the test I mentioned. This is a 1300mah Icom battery pack - no other brand name mentioned anywhere on it but there is a bunch of printing in Japanese on it also. I checked the voltage this morning and it is 7.60 volts so it has lost very little (0.02 volts) since last night. Since these packs are quite expensive I'm putting it back on the charger now to see if it will come up to full voltage. Is it possible this has a protection circuit? Would I still see 0.13 volts on it if the protection had kicked in? At this point it's not possible I can buy another pack so I'll just have to live with this one for now if I need the radio. 
The charger for this is a wall wart and I doubt it has any thing in it beside a rectifier and transformer. It plugs into the side of the radio and much like a cell phone you see the charging indicator on the radio display. So I assume circuitry inside the radio regulates the charging since the charger plugs into the radio and not directly into the battery pack. The charger indicates a 200ma DC output. I probably had it on the charger yesterday for 3-5 hours and as I said no overheating at all while charging - only 11° above ambient room temperature. I'll post later what I find - if it fully charges and then I'll do a run test and monitor the battery temperature.


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## SilverFox (May 3, 2007)

Hello Josey,

Protected cells will show close to 0 volts when the over discharge protection circuit kicks in. That does not mean that the cell voltage is close to 0 volts. To measure the cell voltage, you need to charge the cell for a second or two to reset the protection circuit. Let it sit for a few minutes, then measure the voltage.

Tom


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## SilverFox (May 3, 2007)

Hello Matrixshaman,

Sorry, I misunderstood what you said concerning charging.

Keep an eye on things and do a full charge. Let it sit for a few minutes then measure the voltage. Hopefully, it will be above 8.2 volts.

Icom battery packs are still available, but you may need to do some checking. Here is one site that sells Icom packs.

Tom


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## snakebite (May 4, 2007)

that pack will be just fine.
it was 0v because it had shut down.
i have a vx7r that the spare packs were bought from a hamfest from someone who insisted they were shot.they had hit the lvd and read 0v
a maha test shows slightly more than rated cap.
dont worry about it.
what ya got? ic-t90?


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## matrixshaman (May 4, 2007)

I let it charge until the display said the charge was complete. I pulled it off let it sit a minute, turned it on for a minute then off and read the voltage at 8.25 volts. And fresh off the charger the battery was only 10° F warmer than ambient room temp. I haven't had a chance to let the radio run a while but my guess is they are more or less okay. Silverfox - no prob - I didn't really explain all that I had done and as always your input is very welcome. Snakebite - I packed up the radio and it's really been so long I'd have to confess I don't know the model but it's a tri-bander IIRC. Nice radio except poor filtering for cross band interference.


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## SilverFox (May 4, 2007)

Hello Matrixshaman,

The picture started off a little fuzzy. Now that it has cleared up, it looks like you are good to go.

Tom


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## nanotech17 (May 4, 2007)

I have these cell from DX - http://www.dealextreme.com/details.dx/sku.722
I put 2 of these in my Cree Huntlight and accidently drain to almost empty on 1 of them.
When i check with DMM 1 of those read at 0.19v.
And i tell my self how can i be so careless,nevertheless i put it in the dsd charger using the nokia 6630 power adaptor and after 30-45 minutes of charge the dsd indicator shows green!I checked with DMM and it read 4.2v!
Put it back in one of my flashlight and it's working until now


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## etc (Nov 18, 2008)

SilverFox said:


> Hello Josey,
> 
> Protected cells will show close to 0 volts when the over discharge protection circuit kicks in. That does not mean that the cell voltage is close to 0 volts. To measure the cell voltage, you need to charge the cell for a second or two to reset the protection circuit. Let it sit for a few minutes, then measure the voltage.
> 
> Tom





Old but valuable thread. 
I just had a scare, my 18500 AW cell got discharged to 0. I thought it was supposed to be protected?

Well, I did the above and a few mins it's right at 3.6V. Bizarre.

I am using the Pila charger and trying to stop at 4.1V to increase the number of recharges, (1500 vs. 500, on 4.1V and 4.2V, respectively)


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## SilverFox (Nov 19, 2008)

Hello Etc,

You are not reading the battery voltage.

You are reading a tripped protection circuit voltage, which is near 0 volts.

To read the batteries voltage you have to reset the protection circuit by placing the battery in the charger for a second or two. Then remove the battery and check the voltage.

Tom


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## SilverFox (Nov 19, 2008)

Hello Etc,

I am not sure you will be successful in using the Pila IBC charger to charge to 4.1 volts.

Take a look at a charging algorithm that charges to 4.2 volts. Here is one from TI.

You will notice that the constant current portion of the charge continues until the target voltage (4.2 volts in this case) is reached. Then the charger hold the voltage at 4.2 volts while the current drops off. If you stop the charge when the voltage reaches 4.1 volts, you will not complete the charge.

The Schulze, and some of the other hobby chargers, have a setting that uses 4.1 volts as the target voltage. This is what you need to use to charge to 4.1 volts.

Tom


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## etc (Nov 19, 2008)

Thanks for the info.

These protected 18500 AW cells suddenly cut off without a warning, unlike primaries which slowly dim to nothing.

I am going to time runtime of Surefire 9P with Malkoff M60 and 2x18500. I have a feeling I am not getting the entire runtime.


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## Mugrunty (Dec 4, 2008)

This looks like a nice topic to post a reply to! I received a few li-ion battery packs from one of my professors. They ALL read 0v from the terminals. These had protection circuitry, so I opened one of the packs up. Both 18650 cells were at very close to 0 volts. Free Batteries are just too good to throw away, so I carefully monitored the cells as I manually charged one of them using a CC-CV technique. The cell behaved funny at first...drawing lots of current and not rising too much in voltage. About an amp and rising to 2.5 volts. I slowly let it sit on the charger with a slow 200mA charge. Eventually it rose to 3.6 volts. At this point I charged it at about 800mA until it reached 4 volts. I then ran LEDs off of it and such. Eventually, I charged it the rest of the way to 4.2 volts. I made a really funny flashlight out of it using a switch and an LED. It would make you guys laugh unbelievably hard. I was just foolin around. Anyway, It's been about a week now and its still at 4.06V. 
It seems to be an 18650 cell by Energytec, 1500mAh. Here's a pic of the "flashlight". Not my best work... LOL x 10

BTW, the battery hasent been charged in about a week and still holds a charge. The internal resistance isn't that bad either. Of course it doesn't drop at all with the 20mA load of the LED. It can easily handle 2 amps. The cell recouperates nearly instantanously back to 4.04v when the load is removed. I'll be getting a universal charger soon with charge/discharge funciton on it. It has graphing software to monitor temp, current, and voltage. I'd like to run it through a cycle to see what the capacity is at.














PS. don't worry, there is a current limiting resistor in the heat shrinking!


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## LumenHound (Dec 5, 2008)

Mugrunty said:


> This looks like a nice topic to post a reply to! I received a few li-ion battery packs from one of my professors. They ALL read 0v from the terminals. These had protection circuitry, so I opened one of the packs up. Both 18650 cells were at very close to 0 volts. Free Batteries are just too good to throw away, so I carefully monitored the cells as I manually charged one of them using a CC-CV technique. The cell behaved funny at first...


 
If you checked the voltage of those discharged cells at the battery terminals and found them to be very near zero then you should err on the side of caution and take them out of service for good. 
You don't know how "used" they are and what they have been subjected to, load wise.
Best to play it safe and start with a pair of new cells for whatever project you may end up using a pair of 18650's in.


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## matrixshaman (Dec 5, 2008)

Mugrunty - if it makes light it's a good light  - thanks for the pics and thanks for everyone who resurected this long forgotten thread. I'm curious Mugrunty what type of charger you are getting with all those functions? I really like being able to keep batteries alive - even old and ones most people would advise to throw away. You just need to be very aware of how you deal with them. I've got old 18650's from a laptop probably 8 or 9 years old now that sat for years unused and were brought back from very low voltages to where they are being used now almost every day in a couple lights. None have had any problems.


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## n3eg (Dec 5, 2008)

I got a good laugh out of a flat LiIon Nextel single cell battery today. It ran through our Cadex 7400 at the shop 3 times yesterday, starting at 51% and winding up at 34%. Just for the heck of it, I ran it again today. It started at 24% and finished at 9%. It was also charging at 4.08 volts instead of the usual 4.20 volts. 

Sometimes I've been able to recover a Li battery, but haven't had long term good results with them. I wouldn't bet my butt on them with a radio in my back pocket...


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## Mugrunty (Dec 12, 2008)

I didn't see that people replied here. I gave up checking after a few days. I was too busy trying to help my Sony Aibo. He is having battery troubles.
Anyway, about the "charger" I used to charge this cell. It was actually just a Bench power supply with CC/CV control. I think the specs were 0-30V @ 0-5 amps. The new charger I got is the coolest thing ever. I don't have pics right now, but the name is: RC-power BC6. I think you can google it. It is a computerized balance charging system. You can charge ANY cell chemistry...Li-ion, Li-poly, Li-Fe, Ni-MH, Ni-Cd, or Lead acid(Pb). (OK, so not every battery...but the vast majority). 

It allows you to select the charging current from 0.1-5A, or select the discharge current from 0.1A-1.0A. It came with many connectors, and temp sensor, and a USB cable for interfacing with a PC. You can make awesome discharge/charge graphs! I'll stop explaining it just because you can find most of the information on the web. Unless you have a question. 

Here's a quick picture of a discharge graph from an old 18650 cell. I wanted to know why Aibo was only lasting 4 minutes. You can see the internal resistance has suffered, causing the voltage to sag too much under the relativly high load.






You can see that I only pulled about 381mAh out of it during that time period. I had the voltage cut-off set at 3V, but I stopped it early. You can also see that the votage quickly dropped to 3.5V. (triggering the fuel gauge to think its empty) Or course, upon removing the load...the voltage would raise back up to above 4v in some cases.

Anyway, awesomly cool charger I picked up for about 50 bucks on ebay. I had so many batteries laying around that I needed this. I love how it keeps track or everything...you can even tell it to cycle a battery 1-5 times! Not to mention the li-ion cell balancing stuff! Extra cool. 

Don't wanna make this post too long and boring, but the "light" I built is still working fine. 4.16V! I might run a discharge test at about 200mA to find it's real capacity. Hopefully it won't blow up (knock on wood), but I can't help but play around with a FREEEEEEEEE 18650 cell.


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## matrixshaman (Dec 13, 2008)

I've seen some others here buy the BC-6 and looked at one myself. There are a few in that same class and I'll eventually get one. BTW the Sony Aibo is cool - got one of the knockoffs of it a few years back that was a lot less $$ but still fun.


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## PsychoPilot (Dec 15, 2009)

LuxLuthor said:


> Being the never ending noob that I am....how does one go about testing the internal resistance of batteries? Is it just a matter of putting the DMM on Ohms and touching POS & NEG terminals?


 


UncleFester said:


> *ABSOLUTELY* do not do that. If there is ANY charge in the cell it could instantly take out your meter.


 
I did this 

How would I know if I damaged my multimeter?


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## TooManyGizmos (Dec 15, 2009)

See if it will properly read a resistor with a known value , such as 2K ohms.


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## johnyradio (Dec 29, 2013)

VidPro said:


> the ones that were all the way low, were total trash, on charging they took WAY more power in than they output, and self discharged in less than a day. the ones that were very low, but not all the way, were applied, fruitlessly , they were a total waste of time, eventually self discharging, heating on charge, and having little capacity.



i have read that after a couple weeks, the chemistry of a li-ion changes and becomes dangerous. the article said if the battery takes more than 1 minute to revive, then it's a goner.


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## johnyradio (Dec 29, 2013)

SilverFox said:


> The amount of damaged caused by over discharging is related to the amount of time the cell is in the discharged condition



i've read it's safe to jumpstart a li-ion if it has been discharged for less than 2 weeks.


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## johnyradio (Dec 29, 2013)

Josey said:


> If the battery gets too low, the light will start to blink. If I don't catch it right away, the cell will pop down to 0 volts, or just above.



"pop"? That sounds like maybe the behavior of a built-in protection circuit. 

The protection circuits that are built into SOME li-ions prevents over-discharge, by turning off the cell when the voltage drops to about 2.5 volts. So as the battery gets used up, when it reaches about 2.5 volts, it will "pop" to 0 volts.


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## Bullzeyebill (Dec 29, 2013)

johnyradio said:


> i have read that after a couple weeks, the chemistry of a li-ion changes and becomes dangerous. the article said if the battery takes more than 1 minute to revive, then it's a goner.





johnyradio said:


> i've read it's safe to jumpstart a li-ion if it has been discharged for less than 2 weeks.



Would you please site the source of your information, as noted above as "I've read....."

Bill


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## johnyradio (Dec 29, 2013)

Bullzeyebill said:


> Would you please site the source of your information



i knew you were going to say that. i closed the durn tab... trying to find it...


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## johnyradio (Dec 29, 2013)

http://batteryuniversity.com/learn/article/low_voltage_cut_off


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