Should I throw out batteries that had been discharged down to 2.0v?

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).

I know the M43’s drain value with button light off is ~20 μA (~80 years). With the back lit button on it still is only ~80 μA (~20 years).

I haven’t measured that of the MF01.

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.

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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……BU-304a: Safety Concerns with Li-ion - Battery University

These battery never seen anything below 3.5v since I bought them. I’ve been using my D4 all the time since it’s small and bright so I forgot about the big guns lol. I’ll see if they can hold charges and if they get too hot or not. But yea it’s crazy how fast it got drained

I agree with sp5it. They will be fine.

So… I can’t find my user manual but seems like my charger has the function of detecting internal resistance (pic 1) . Can someone tell me if my 2nd pic is what I’m looking for? Sorry if this is a dumb question

What charger do you have?

I have the Notecore SC4 superb charger

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: Test/Review of Sony US18650VTC6 3000mAh (Green)

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.