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Hi I've have a couple of batteries of these two types, some of them are below 2,5V making me unable to make a CAP test on them, whenever I try my Foxnovo 4-Slots Intelligent Battery Charger beeps four times and "seems, not sure" to remove some voltage from the battery?

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The one with the purple top has "A NJGA59 034688" written on it. The one with the orange top has "C IEOFJT4 077773" written on it.

They come from a semi-old dell laptop battery, from Toshiba and Sanyo I believe.

Athax
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  • Have you googled about letting the voltage on a Li-ion battery drop below 2.7 volts and what you should expect in terms of them being serviceable? If not, why not? – Andy aka Aug 05 '17 at 18:20
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    I don't know what kind of cells those are. But you can try to trickle charge them up above 2.5V. Use a current limited bench supply (maybe 100 mA or so). Or you can use a resistor to limit the current to something under 100 mA. You can try this for around 30 minutes or so. If the voltage does not come up, the cell is probably beyond hope. The usual rules apply. Under no circumstances should you let them charge above 4.2V, nor should you float them at 4.2V after they are fully charged. – user57037 Aug 05 '17 at 18:21
  • The idea of the trickle charge is just to get the cell voltage up to a point where the foxnovo will try to charge them. – user57037 Aug 05 '17 at 18:22
  • https://electronics.stackexchange.com/questions/219222/is-draining-a-li-ion-to-2-5v-harmful-to-the-battery – Andy aka Aug 05 '17 at 18:24
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    Thank you very much guys, you're all been a big help! Sad to hear that no one recognize these batteries yet. I'll try tickle charge them, would using the foxnovo charger and just pull the battery back and releasing it tickle charge them? – Athax Aug 05 '17 at 18:40
  • @mkeith What does float exacly mean? – Athax Aug 05 '17 at 18:42
  • Float charging is holding charge voltage fixed at a specific voltage level. CV charging. It is OK for lead acid batteries (provided the voltage is not too high) but not safe for Lithium ion or polymer batteries. – user57037 Aug 05 '17 at 18:58
  • So if i charged it up to 4.2 and take it off the charger and store them, would that be okay? – Athax Aug 05 '17 at 19:07
  • @Athax,"if i charged it up to 4.2 ... and store them"... No, this won't be okay. Fully charged Li-Ion batteries are prone to some chemistry fatigue. It is recommend to store Li-ion batteries with about 60% charge, when they show 3.6 -3.7 V no-load. – Ale..chenski Aug 05 '17 at 20:32
  • @mkeith, actually this mode is officially called "pre-charge mode". The trickle-charge is when a battery is fully charged, and when drops below 4.05V (or something, due to initial self-discharge), a charge is applied again. – Ale..chenski Aug 05 '17 at 20:40
  • Yes, the chargers that do this refer to it as pre-charge. Perhaps my terminology is not strictly correct or identical to what is used in the literature. But I doubt the OP is familiar with that terminology. I should have maybe used a different term. The point is, just charge them up SLOWLY to 3V or so, and then see if the charger will recognize them. – user57037 Aug 06 '17 at 00:07
  • @mkeith Ahh okay, so how do decrease the voltage again? Can I for an example run a motor and their voltage should decrease? – Athax Aug 14 '17 at 10:18

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These are the classic 18650-type OEM batteries, Li-ion chemistry, charge voltage should be 4.2 V. Their design capacity might be 2500 - 3000 mAh, depending how long ago the were made.

If some are "undervoltaged", below 3.0 V (or even to zero), you can try to recover them by applying "pre-charge" current, 100 - 200 mA, until they get to 3.3V-something, then a normal charger will work. Be aware however that the battery capacity might be substantially reduced, down to 20 - 40%, or it could remain dead.

Ale..chenski
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  • Thank you but I've read so many scare stories by now about reanimating the batteries. I'm just considering getting rid of them. I've tried charging two of them with 0.50a that had 3.6v but they got really hot around 60C. So I just stopped it and trew them to the battery bin. – Athax Aug 06 '17 at 15:39
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    @Athax, Why 500 mA? Dodn't you listen to advices here? 500 mA is too much for pre-charge of dead/overdischarged batteries. With 500 mA and 60C overheat, you came too close to being another example of a scare story. – Ale..chenski Aug 06 '17 at 16:42
  • Oh no these wasn't dead batteries, there was two in the pack that had over 3.6 voltage and would be recognized by my foxnovo. – Athax Aug 08 '17 at 09:34
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This is what worked for me when I had couple of unprotected Li-ion batteries in the past. I don't know if it's a good procedure but had heard from somewhere that this was safe.

  • The main purpose I was doing this because 4.2 V chargers were unable to detect these batteries once they go beyond 3.1 V

  • I had an Arduino Uno board which had 3.3 V power pin which can hardly provide around 50 mA power.

  • I used to connect individual battery cells to 3.3 V through a series resistor of 100 ohms (1/2 or 1 W) & GND pins for 10-15 mins to trickle charge them.

  • Battery voltage was raised upto around 3.2 V by this technique.

  • Later they were removed & connected to 4.2 charging circuit which used to detect the batteries.

Nihal
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  • I'll consider doing this as I have an Arduino Nano! Thx for it, does this work for batteries all the way down to 1v? – Athax Aug 05 '17 at 19:29
  • NOT recommended. But it should be OK if you put a resistor in series between 3.3V and the battery. Maybe about a 33 or 47 Ohm resistor. The resistor may get a bit hot. If the battery gets hot at all, remove it. If it doesn't get hot, you should be able to leave it for up to an hour or so. If the voltage does not come up and stay up after an hour, the battery is probably not recoverable. – user57037 Aug 06 '17 at 00:11
  • @Athax yes even zero voltage Li-ion battery I had trickled charged. And I think it's safe as Arduino Uno board's 3.3 V source is capable of only 50 mA current. You check the current rating of 3.3 V voltage regulator of Arduino Nano from its datasheet before proceeding. – Nihal Aug 06 '17 at 01:09
  • @Nihal, when a regulator says 3.3V 50mA, that usually means it can supply at least 50mA. It may supply quite a bit more. Typical regulators do not have precision current limits like a good bench supply. So if you directly connect a 3.3V regulator to a discharged cell, you really don't know what the current will be. This is why I recommend the resistor between cell and regulator. – user57037 Aug 06 '17 at 17:56
  • @mkeith Yes it's better to use a resistor in series with the battery. I found this procedure back in my school days and I didn't use any resistor that time & both battery & Arduino's regulator were working normally as expected even after undergoing such a process. I have updated my answer as per your suggestion. – Nihal Aug 06 '17 at 18:14
  • I think I'm ditching these batteries, two of them had a charge on above 3.6v and my foxnovo would recognize them but they got quite hot around 60c. So I cancelled the CAP. – Athax Aug 08 '17 at 09:37
  • If they are getting too much hot or getting swollen means the batteries have reached their end life. It's better to ditch them only. – Nihal Aug 09 '17 at 12:49
  • Yeah I just got a couple more laptop batteries, and their temperature is not getting to uncomfortable temperatures when charging, some of them even stays completely cold! :) – Athax Aug 12 '17 at 14:29