# Bringing a dead Li-Ion to life



## Igor Porto (Apr 16, 2010)

Hello fellow flashaholics,

A few days ago I had a disturbing thing happened: I overdischarged a protected 16340 Li-Ion battery, and the protection circuit kicked in. When I went to recharge it, the charger didn't recognize it. I measure the battery's voltage and it was a few mVs, almost zero. Nothing I did was able to bring it back, so I thought it was dead.

A few minutes ago I went to throw it away and got thinking that somewhere around here I saw another post about this, and they recommended applying a slight charge to the battery with a higher voltage. I went to try it out, I had nothing to loose, but I thought how high is enough? I saw a 9 volt battery, half dead actually measuring 7.14 V, and thought: double the cell voltage seems OK as a starting point, if it doesn't work I'll try a higher voltage. I then touched the negative to the Li-Ion negative, and used a wire to touch the positives. I did it for 3 seconds. Measured in the multimeter and had 1.358 V. Put it in the charger and voilá, it's charging! 


BTW, I don't have an intelligent charger that refreshes or cycles my Li-Ion (if anyone knows a good one, please tell me!). So once a month I discharge them using a resistor, calculated to discharge them at 1A approximately. Sometimes, with some batteries if I forget to turn the resistor off before the battery runs out of juice, the protection circuit kicks in and the battery gets stuck. I hate discharging them to keep the electrons flowing, because I have a lot of Li-Ions. If anyone knows a better solution I'm all ears.

Thank you guys! :wave:


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## kramer5150 (Apr 16, 2010)

You shouldn't be deep discharging them like that. Lithium ion and Lipo cells "like" to be kept at or near full charge. Just top them off every 2-4 weeks and you're good to go.


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## VidPro (Apr 16, 2010)

cool
when hitting the low end of the protection. the RATE that you discharged at , will somewhat determine how "soon" the protection kicked in, AND therein how far the cell actually discharged.
so when pulling it down Slllllooooowww , you actually discharge it further.
when you discharge faster, the voltage of the battery is pulled lower, as you know, and the protection triggers sooner.
the cell then rebounds with a higher voltage, it is easier to get charging again, and it wasnt WAY low discharged.

so use your same method, and just punch it up faster ,,, or get one of them cheap hobby chargers , only because they are cheap now. then learn all the things you can do "wrong" with it.
they dont discharge so low, stopping at 3.0V or even higher if you want. and give you pretty numbers you can contemplate the State of your Investment (SOYI) with 
Also tricks with zener diodes , and stuff to stop discharging at higher voltages. 

bringing it up with the 9V works out good, because the current rate itself will go nice and slow, because the 9V cant really pump out some excess current, so that was a fair power supply to use.


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## Igor Porto (Apr 16, 2010)

Yes, I don't often discharge them like that, but this time I forgot it discharging 

But isn't there a warning that keeping Li-Ion fully charged for long periods is bad for the battery? All my batteries are always charged but I don't use them all to at least discharge partially in a couple of months. What do you suggest?


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## Igor Porto (Apr 16, 2010)

Thanks VidPro for the input. Actually I use two cheap chargers: Ultrafire and Trustfire, but luckily they don't overcharge them (as other users report around here). The Ultrafire charges them to 4.18 V and the Trustfire to 4.22. And they don't charge further than this even when I leave the batteries in them for a longer time.


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## VidPro (Apr 16, 2010)

Igor Porto said:


> Yes, I don't often discharge them like that, but this time I forgot it discharging
> 
> But isn't there a warning that keeping Li-Ion fully charged for long periods is bad for the battery? All my batteries are always charged but I don't use them all to at least discharge partially in a couple of months. What do you suggest?


 
seems the battery doesnt like being stuffed at EITHER end, way high or way low. One reason for the protection is to keep them out of the worst places.
in some perfect world storing them at about 50% is better than high or low. but i think that world is only 1/2 Perfect 
I really do have some stuff that has so much battery, and will get so little runtime, that if i set the battery to 50-60% , the 50% of available would be enough .


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## kramer5150 (Apr 16, 2010)

*Yes, I don't often discharge them like that, but this time I forgot it discharging.*
There really is no need to deep-discharge like that at all, unless you are cycling and matching cells by their capacity. But its not necessary to be doing that as part of routine maintenance.

*But isn't there a warning that keeping Li-Ion fully charged for long periods is bad for the battery? All my batteries are always charged but I don't use them all to at least discharge partially in a couple of months. What do you suggest?*
If there is, I personally have not seen one. And... such a warning would turn the laptop PC, and portable consumer electronic industries upside down. All of which maintain Lithium Ion cell voltages at/near full capacity.


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## Qoose (Apr 16, 2010)

A number of laptops that I've used actually have a tool that lets you dictate the charge level you will top out at. I used to run my laptop charged to 75%. Also, they recommend that if you will store a battery that won't get much use, keep it at 50% charge and tuck it in a cool place.

It kinda makes intuitive sense that this would be healthier for a battery. However, a half full battery is not quite as useful as a full one.


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## Igor Porto (Apr 16, 2010)

Kramer I usually just discharge them about half or to 30% maximum, always monitoring the voltage under current of the resistor. When it reaches this point I usually store them or recharge.

There's a website about batteries that I use as reference. In one article it says:

"Aging is a concern with most Li-ion batteries. For unknown reasons, battery manufacturers are silent about this issue. Some capacity deterioration is noticeable after one year, whether the battery is in use or not. Over two or perhaps three years, the battery frequently fails. It should be mentioned that other chemistries also have age-related degenerative effects. This is especially true for the NiMH if exposed to high ambient temperatures.

Storing the battery in a cool place slows down the aging process of the Li-ion (and other chemistries). Manufacturers recommend storage temperatures of 15°C (59°F). *In addition, the battery should only be partially charged when in storage.*"


"Subject to aging, even if not in use — storing the battery in a cool place and at 40 percent state-of-charge reduces the aging effect."

http://www.buchmann.ca/chap2-page7.asp



Often people who use laptops always use them plugged to the outlet, thus keeping the batteries fully charged and inert. Coupled with the high temperatures of the computer, the aging process is really fast. I see a lot of people complaining about their batteries dying in less then a year.

On Apple's website there's a note regarding this:

"Standard Maintenance
For proper maintenance of a lithium-based battery, it’s important to keep the electrons in it moving occasionally. Apple does not recommend leaving your portable plugged in all the time. An ideal use would be a commuter who uses her MacBook Pro on the train, then plugs it in at the office to charge. This keeps the battery juices flowing. If on the other hand, you use a desktop computer at work, and save a notebook for infrequent travel, Apple recommends charging and discharging its battery at least once per month. Need a reminder? Add an event to your desktop’s iCal."

http://www.apple.com/batteries/notebooks.html


Well that's the knowledge I've been used to for a number of years. Correct me if I'm wrong.
The good thing is I've never had a Li-Ion battery go dead because of deterioration or too much cycling. Even my old iPhone (almost 3 years old) has good battery life like if it was new. But that's because I take care of them. I once heard: the best way to keep your batteries is to USE them! 

Cheers!


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## kramer5150 (Apr 17, 2010)

I guess I never factored in long-term "dormant" storage. I have to admit, storage of this type is something I have no experience with. I was assuming you'd be using the cells periodically, and for that they should be kept on standby fully charged, topped off periodically.

Good to know you are not _deep _discharging them all the time, thats generally a bad idea.


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## Igor Porto (Apr 17, 2010)

Sometimes I'm afraid my 18650's get dormant, like two or three months charged in the drawers until I need to use them. I may start to store them half charged and top them off when needed.


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## kramer5150 (Apr 18, 2010)

Igor Porto said:


> Sometimes I'm afraid my 18650's get dormant, like two or three months charged in the drawers until I need to use them. I may start to store them half charged and top them off when needed.



Primaries are a better option if you are using your light that infrequently. Lithium Ion cells like to be used regularly, maintained at or near full charge, and never deep-discharged.


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## mdocod (Apr 19, 2010)

Find a happy medium, charge to ~4.0V for storage, so you have a decent charge on tap if needed and a state of charge that isn't going to age the cells substantially faster than the ideal 40-50% state of charge. 

Eric


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