I’ve read about people reviving over discharged batteries, but I personally would not take the risk.

Hold on. You unscrewed the tail cap, so you’re sure parasitic drain is zero? And how long have you not used the light? If you look at a discharge curve, the voltage takes a nose dive below something like 3.0V. This means if your resting voltage is something like 2.0V, then it also takes very little time to recover to something like 2.9V. I’ve had it once with an AW cell, although it wasn’t discharged to that low level.

It’s possible that the battery has discharged from something like 3.5V to 2.0V in three months due to parasitic drain. But you said you unscrewed the tailcap. It sounds very unlikely that it’s self discharge. What light was the VTC6 in?

They should be okay just he careful with them. Some high drain cells are made to be drained to around 2.5v. The reason the voltage jumps up so quick is there is no or low capacity below around 2.5v-3v

I’ve got the MF01 too. I also have the feeling that below certain voltage parasitic drain is fairly high. As a matter of fact I have one next to me right now unscrewed as well which I normally don’t do. The odd thing is that we are told not to discharge below 2.5V, but pretty much any (good quality) charger will charge over discharged cells without problem or warning.
I think you’re safe, but I see no reason to take unnecessary risks. Hopefully other people will chime in. Otherwise you might want to contact HKJ and ask for advise.

Charge them and use them. I did that many times. Except dead by age/cycles batteries should work.
Mike

I would charge them up and then let them rest for awhile. If they hold their charge at around 4 volts, they should be fine. But that’s just my opinion.

I had a similar concern with some laptop batteries that had very low voltage, around 2 volts if I remember correctly. I charged them up and they’ve been fine since then. They’re only around 1,900 mAh, but hold their voltage at around 4.1 volts.

But if you are really concerned about them, then just recycle them for piece of mind.

Regarding a safety feature, protected batteries usually turn off at around 2.75 volts so it appears yours are not protected.

Out of curiosity, what flashlight were the batteries in?

NeutralFan wrote:

Out of curiosity, what flashlight were the batteries in?

It was the MF01

If the cells are damaged internal resistance will be high. That is one way to tell.

If you have an analysing charger (Opus, Miboxer, Zanflare, etc.), you can do more tests, but in general, I don’t worry about “dead” cells.

I’ve gotten laptop pulls that’ve been sitting unused for years, some cells bricked to 0V and not taking any charge at all, but the other cells revived just fine. I still use them in my EDC light and others (headlamp, etc.) where I can keep an eye on them, but haven’t had any issues yet.

Especially after being in service for so many years (old panny-As!), they might have only 2/3 the capacity as when new, but they’re still chugging along in low-stress lights.

Unless you have the required equipment to charge them very slowly back to 3.0V(50-100mA) and they weren’t discharged that low for very long, I wouldn’t try it.

However, if that 2.0V was only for a brief period of time, then you recharged then, then it shouldn’t be a problem.

The parasitic drain in the Astrolux MF01 must be pretty high to drain 4 batteries in about 3 months. Are you able to measure it?

My Meteor M43 with a lighted switch seems to take forever to noticeably drain the 4 30Q batteries. I don’t use it that much, but it will sit on the shelf for months at a time with the switch staying at blue (meaning fully charged).

NeutralFan wrote:

The parasitic drain in the Astrolux MF01 must be pretty high to drain 4 batteries in about 3 months. Are you able to measure it? My Meteor M43 with a lighted switch seems to take forever to noticeably drain the 4 30Q batteries. I don’t use it that much, but it will sit on the shelf for months at a time with the switch staying at blue (meaning fully charged).

I have personal seen batteries that measured well below what most would consider “throw them away batteries”. These were never used that I know of but the seemed as they had just rolled off the factory line.
http://budgetlightforum.com/node/20513
.
I would watch them very close, see if they heat up while being charged or in use. I wouldn’t be so crazy about using them in series either or asking the cell for high current. One bad cell can make a very bad situation. Parallel should be fine or single cell use. I would continue to use them but I would keep a sharp eye on them. As soon as your batteries are depleted, give them a charge even if its only a partial charge. Never leave them in a stressed depleted state.
More info here…..http://batteryuniversity.com/learn/article/safety_concerns_with_li_ion

sp5it wrote:

Charge them and use them. I did that many times. Except dead by age/cycles batteries should work. Mike

I agree with sp5it. They will be fine.

What charger do you have?

If you look at a lot of LG datasheets they use 2.0 discharge limit to get their mah rating. Look at the hg2 datasheet

I’ve recovered 1 volts and lower cells from tool packs and laptops and have been going strong
Also 0 volt cells a few times that e switch lights killed. Most recover full mah

Charge them and use them as mentioned before.

Sony VTC6 are rated 3000mAh (3120mAh typical) at 2.0V cut off, so it’s likely that they are still safe. Just don’t make it an habit.

Here’s a test/review by HKJ that lists 2.0V as end of discharge voltage: http://budgetlightforum.com/node/48366

Based on that you’re probably OK. After watching plenty of videos of cells burning I’d pitch anything that discharges below listed tolerances.

no, dont thorw because such a silly thing, it also cause pollution to enviroment, just charge it at low current to normal voltage, and make sure never discharge it too low

The battery you use has 3A-hr capacity, it would take 7uA leakage to drop 10% in 5 years. If the batteries in the light went to 0 capacity in 3 months, guessing it was at 1/2 capacity to start, the leakage of the light is about 700uA.

Either you did not unscrew the cap enough, or your batteries all have a VERY high leakage due to a protection circuit or some other strange phenomenon.

I have many cells that have bee salvaged from 2 volts, (some even from 1.7 ~ 1.8 volts) and been working fine since. the thing is to know its a brand name quality cell, SLOW charge them back up to roughly 3.7 volts, then do some IR (Internal Resistance) tests, capacity tests, and load tests while monitoring temperatures of the cell. (do all this in a garage with ventilation & safety precautions in place) I have thrown out/recycled cells that have never been discharged to low levels, but their IR was high and they heated up during charging. and i have soem cells as mentioned above that were as low as 1.7 volts, but their IR tested at 50 ~ 60 range and they still tested close to their rated manufacturer capacities, and sill in use and have no problems. If your not experienced with Lithium Ion cells or know how to test & recover them, then it’s best to recycle them.

Check the internal resistance. If it’s high you gotta chuck ‘em.