If you don’t mind my asking, why do you want to do this?

Many charger will, HKJ inform about this in his tests. Manufacturers will often call this ”0 volt activation” and will use a low current when the cell is too low, many integrated charger will also be able to do this (but not with current limiting).

For example : Xtar MC1/MC2 plus.

You can also use a voltage source (a power wall plug, another cell etc..) with an appropriate resistor to limit the current to 100mA for example, until the voltage is high enough to charge in your charger.

But while the datasheet specifies 2V as the minimum voltage, the rated cycle life is given for a 2.5V cut-off and this should be the minimum voltage for normal use. There is practically no energy between 2 and 2.5 V so there is no point in discharging to 2V anyway.

Vapcell S4 Plus is quite good, but does not perform a really zero volt activation (leaving light on ).

But my “XTAR VC2 Plus MASTER” came through! From almost zero!!
However, the charging current is 0.5A or 1.0A and that’s a bit rich for small cell’s.

So when the cell responded with proof of life, I transferred it to the Vapcell to be charged at 0.2A

Often a NiXX dumb charger will do just fine.
As has been stated already, you REALLY don’t want to go that low. I personally don’t like to go below 3.0v, 3.2v actually.

Dumb chargers are great for just getting ‘em started. They pick up to 3.whatever almost in seconds. Then stick ‘em on a charger charger which coddles ‘em the rest of the way.

The Opus BT-C3100 will also charge at very low voltage. I haven’t done that with Li-ion, but with NiMH many times.

NeutralFan wrote:

The Opus BT-C3100 will also charge at very low voltage. I haven’t done that with Li-ion, but with NiMH many times.

Forgot where the cell came from, mightta been one of the mag-ring Sofirns I thought was locked out, but my trusty Ope didn’t touch the cell ‘til I jump-started it with my LK101 for a few seconds.

2V discharge is very dangerous for lithium cell and can begin to cause physical change in the battery electrode and electrolites. I recommend you be careful with using the battery in the future because it is at larger risk of damage.. the best is to make sure cell voltage do not go below 2.8V.

vidramon wrote:

I do not drain this cells, I got them in this condition

that sounds extra risky

Prudence would dictate that you take those overdischarged cells to a recycling location, out of an abundance of caution.

usually when a cell gets drawn down below 2.5v it should be recharged immediately. Letting the cell rest for long periods at 2v increases the risk of overheating upon recharge.

otoh, your NMC chemistry is generally considered relatively safe from cell reversal upon overdischarge. Are you feeling lucky?

You ARE breaking safety rules by recharging a cell that was so low. Plus having been at low voltage for some? time increases the risk.

be careful, good luck..

Thanks for your guys’ supports on XTAR chargers. More details about 0V activation function here:

One note on 18650 lithium cells that are at 2.0 volts would probably be okay to change if you use a battery tester that has a temperature sensor to monitor the battery cell temperature and set the temperature for no more than 32*C at the most and use not more than 80 milliampere of current until the battery voltage comes up to 3.0 volts or higher your current amp hours rating might be compromised in some way might be minimal to major or if you are lucky not at all

Now for battery cells that are below 2.0 volts

( or to a voltage not less than one volt less than one volt is useless to even attempt to charge the out come is very poor at best )

is a hole another story this can be dangerous if not done correctly but what you should know is that these might become heater cells and not charge at all or if you can get them to charge and are not heater cells the amp hours rate results will be very low because more than likely they have have come to the end of the battery life and should be recycled correctly

If you find some battery cells that can be recovered from being very low on voltage and you get decent amp hours rating and you can charge them at one “c” and have no more than 2*C temperature rise then you are very lucky

The reason I know all this is because I have bought a lot of lithium cell second hand for recycling for a second life in different devices and this is what I have found with my experience with using these battery cells

I hope this helps and one think about using battery cells with battery voltage below 3.0 should be very careful doing so

I have been very successful with recovery of cells that are not below 2 volts but you will find some that have some type issue but my experience has been you can recover most of them if you do what I posted above

On a final note if you are looking for a source for second hand recycled you can find them here

https://batteryhookup.com/products/3-7v-2250mah-panasonic-sanyo-18650-ce...

This where I buy my second hand batteries from most of these battery cells will be below 3 volts but not lower than 2 volts and the amp hour results have been from 2000 to 2280 milliamperes hours so results have been very good

I have bought over a hundred of them so far
And planning on buying maybe a hundred more maybe in a couple of weeks

Disclaimer notice

I am not getting paid for recommending there products or any samples from them in any shape or form

vidramon wrote:

Thank you all for commenting, I succeed with Xtar VC2 !
Lii 500 also failed in this.

Now I get every cell to 3V and SkyRc Mini B6 can do the rest of the job.
Xtar VC2 also succeed with cells 1.9V, no wonder since they have one of the best chargers in the market.

I do not drain this cells, I got them in this condition, my cells are not drained below 3V..
Now I need to charge them to the max, then discharge to read real capacity and measure internal resistance to see condition of the cells.

Are you buying these cells from a Repurpose site —- If these cells have been below 2.5v I wouldn’t fool with them —-EPECIALLY if you have no idea how long they have been in this condition —- It’s one thing to drain a cell below and recharge it back up directly and another to charge one up that’s been sitting like that for no telling how long — I fool with lots of cells (thousands) once they get in that state they aren’t worth saving or the damage they can cause

I was taking apart a battery pack last week with 20 / VTC6 cells in it —- out of no where a cell vented and scared the hell out of me (there’s always a first time) — I’m not sure if I shorted it or what —maybe even a piece of nickel strip could of entered a vent hole —-I feel very fortunate to not have gotten burned or catch something on fire—It was like holding a NEW years Rocket and trying to throw it in the yard

Metal table is not good idea if anything put a plastic cutting board on top of this metal table

As far as the website link that I posted yes they are very responsive to your issues because I have had issue with two battery packs that I bought the battery cell were at 0 volts except for two were at one volt each and they sent me two replacement packs

And to answer your question about battery voltage being below 3 volts yes this can be an issue if the batteries are not name brand battery yes this is very true with name brand batteries it not quite as bad I have tested about 40 of those batteries that I listed and like I said earlier they have not been an issue with them I have charge them at 80 milliamperes unit they reach 4.00 volt and then discharge them at one amp and then the second time I charge them at one amp and did not have any issues at all I did the first ten of them this way I did another 10 the way I test most of them which is set the charging rate at one amp the cutoff voltage at 4.2 volts and look at charging and discharging curves and see what the results are and determine if the battery is useable or not on ( I will do this with batteries that are below 3 volts but I will keep an eye on it until it reaches 3 volts to see how fast it climbs if climbing to fast it goes on the SkyRc Mini B6 with the temperature sensor on the battery )

one note I have changed a lot of battery on this machine and I know what the curves are suppose to look like if the battery is going to be good this in the manual mode not battery type mode which is automatically done then it acts more like the SkyRc Mini B6 dose

One note I do not use the “ SkyRc Mini B6” for looking at the charging and discharging curves of a battery I have a much better battery testing machine for this purpose but this machine does not have a battery temperature sensor cutoff capability’s so I have use the SkyRc Mini B6 tester instead if I suspect a battery has issues with it

One note about this charging device “ SkyRc Mini B6” this charger is only good for charging batteries that below 3 and once you bring the battery up to 3 volt I would highly recommend this that you go into setup and change the battery temperature ( default setting ) sensor settings to 32*C and if you have not bought the temperature sensor I would highly recommend that you do unless you want to babysit the charger while charging battery that have been a very low state-of-charge

Because the default temperature setting is way to high for my taste and I do not want to have a mishap happen while I am not watching it

I have had this charger suspend charging of batteries because they went over 32*C because I do not babysit this charger while it charging I will keep an eye on it

Very important to add a note about voltage stability. 

IF you choose to try to revive low/dead cells, then sure, practice all the cautions above and listed elsewhere regarding charge rate and temperature.  If it goes to full charge nicely, then take it out, measure the voltage with a multimeter (to compare with the charger) and let it sit.  Check it again in a few hours and the next day, then keep checking it every few days or whatever for a couple weeks (or a month).  If the voltage is declining then your cell was damaged enough by overdischarge that it is suffering from self drain and that makes it potentially dangerous...or a hassle, at the least.  The voltage should stay where it's at, only dropping very slightly over time, if at all.  If you get cells that self drain then you can possibly still use them if you wish (if they don't get too hot during discharge or charge) but you'll need to keep a careful eye on them and keep them juiced up.  If they self drain fairly quickly, just recycle them and be done with it - not worth the risk.  You just never know what condition the electrolyte is in after they've drained so low and/or been allowed to remain there for a period of time.  Even if they don't get too hot and even if the internal resistance is higher but still usable for a particular device, the degradation on the inside is not reversible and will continue, and sometimes that can happen awfully quickly such that a rescued cell you thought was ok...suddenly isn't. 

They're cheap enough though lots of sources that it's best to just recycle them unless you know it was a brief overdischarge and you juice them shortly thereafter.  History has shown us that it isn't worth it.

I will suggest 2 models:

1) original Xtar VC4 (but not the newer VC4S ; also I have not tested the VC4L)
2) Miboxer C8 (I tested the earlier revision; I’m not sure if later batches still function similarly, but probably they do)

On the original Xtar VC4, when battery voltage is very low, it will initiate a very low charging current (may take a very long time) for the battery to increase in voltage.
Based on my limited experience, the battery-type indicator will automatically change from NiMh to Li-Ion when voltage goes above a certain voltage, and shift to the correct charging mode.

On the Miboxer C8, the same thing is true. although I would try to manually set the charging current in this case.
Based on my limited experience, the voltage (assuming below 2.0v) will also go up until the charger detects that it may not be an NiMh but a Li-Ion battery, and then shift to Li-Ion charging mode.

I recall the Xtar VC4S, on the other hand, will usually get stumped when batteries voltage is ambiguous (between 1.5v to 2.0v, for instance).

Many other chargers like the Liitokala Lii series will also get stumped and not try to charge the battery when the voltage is in the “ambiguous” level (1.5 to 2.0v = is this a full/over-charged NiMh or an overdischarged Li-Ion? and thus not try to charge)

I have not much experience with Nitecore chargers though. I’ve tested many of the Liitokala and Xtar models only.

(The SkyRC MC3000 will also refuse to charge batteries whose voltages are “ambiguous”, at least need to specify battery type or maybe program the charger to do so?)

~~~~~

Of course, apply the usual safety consideration when attempting to charge overdischarged Li-Ion batteries = monitor if the battery temperature is getting hot, and whether voltage are indeed slowly increasing (but check battery temperature)..