I accidentally discharged eight DMEGC 26E 18650's much lower than expected one night back in August. A very hot night here in south Texas which didn't help the situation. They were so hot, I could barely touch them. In a panic, I threw all of them in the freezer and hoped for the best. I was seriously expecting fire works. It took much longer than expected, but they did finally cool down. When I checked the first one with my Fluke multimeter, I was shocked (figuratively)......1.2 volts!! Because I didn't want to leave them at that low of a voltage until the next morning when I could drop them off at a local business that accepts used batteries for recycling, I decided to throw them on the charger to see what would happen. I charged them up to 3.7 volts and left them all in the kitchen sink overnight. They looked fine the next morning and all had held their charge. It seemed as if they were ok so I decided to fully charge them and use them. They seemed to be operating normally. I've been using all of them since. No problems. I have a total of 25 of them and the 8 that got abused perform just as well as all the rest. 16 of the other brand new ones are used as a boost pack for my electric scooter. The other 9 (there was one extra) are being used for my flashlights.
X Ray, that is to be expected. Just because a cell is over-discharged does not mean that it will get damaged. It takes time for this to happen. I once recovered a few Samsung (26C) cells from a laptop pack whose voltage were at 1.6V or a little bit more (out of 6 cells most were below 2V, and who knows how much time they were left this way). After recharging to a healthy voltage (â3.9V), I left them at rest for 2 - 3 weeks to observe self-discharge. I ended up discarding two cells, as I noticed a little bit of self-discharge in them. All of the remaining four were put into service.
Cells do not die that easily. And if you know how to take care of them, all will be safe.
Can anyone tell me whether or not my Manker 18350 is still safe to charge and use?
Ive accidentally disharged it to 2.6v
Mankers website says the lights that use this cell (E14III & MC13) operate at a âworking voltage 2.8-4.3vâ
(Below is a screen shot of that quote from their website)
The battery/cell itself also says âBuilt in charging circuit prevents overcharging, over-discharging and over-discharge current.â
(Pics of the cell/that quote below)
I was using the light when it flashed the LVP warning and dropped to low brightness. I then stopped using it and put it away.
I then forgot about it for maybe a week or two without charging it back up⌠Oops.
Im pretty sure LVP warning happened at about 2.7v.
Checking the voltage now though shows 2.6v on my DMM, and Im unsure if its safe to charge and continue to use.
Side note: Im also now wondering what the difference is between âover-dishargingâ and âover-disharge currentâ.
Advanced thanks to anyone who can help me out here.
LoL CRC2, some of you are quite âtight-arsedâ with this stuff, but it really ain't that hard. See what I said above.
As a rule, any li-ion cell dwelling at or above 2 V is safe. Period. I won't comment on the impact on cell lifespan, but presuming that low voltages damage cells may be straight out wrong, particularly with quality li-ion cells or batteries. For me, if a cell is between 2.5 V and up to 93.3Ě % of its maximum voltage, it is fine and unless I need to use it I leave it there and store it without qualms.
In contrast, what unduoubtely damages li-ion cells or batteries is consistently keeping them at high voltages or high states of charge! This is a proven fact. Unless discharged to a nice SoC (I use them at or below 65% as a rule) or voltage and removed, laptop packs are usually kept fully charged at all times, resulting in battery pack damage and much reduced lifespan over time. Check this full of wisdom article: BU-808: How to Prolong Lithium-based Batteries.
A cell which has dwelled for some time below 2 V may still be safe, it depends; but cells which are reverse polarized and kept there for some time are better straight out discarded.
I necessarily replaced my smartphone battery in May 2019 (It's a Zuk Z2 Pro, released in April-June 2016), as the guy from which I bought my device didn't gave it good battery care. I still use the same smartphone, and thanks to the thorough care I give to it the battery is still fine (I also bought a top quality battery for it!).
I may buy a replacement battery more or less soon, as replacement stuff for my smartphone is not exactly abundant at this point, and I plan on keeping it in full service for at least another 3 years or more. :-)
Admittedly, I hadnât read the whole thread before asking my question as I should have.
Id have found my answers were already here if I had. (just had a chance to read the whole thing)
Apologies for my bad forum etiquette.
The OP looked a little too over my head at first glance.
So its going below around 1v that these âdendrite crystalsâ start to develop?
I think thats my main worry since I cant see or know if its happening.
As well as not really wanting to severly shorten a cells overall lifespan since theyre not that easy for me to replace.
Fine. The cell actually doesn't cares if you apply a high load to it or not. A âhigh loadâ is a high current or high power load, this means a low resistance load.
So high/turbo is a high load, while a cell at low voltage is nearly depleted, or close to. So, depending what âlow voltageâ is, the driver type and the driver firmware behaviour at low input voltage, the flashlight may still allow you to use high/turbo briefly or even for a long time (this depends on driver type), very soon dim down or flash low voltage warning, or straight out dim down or flash low voltage warning.
Most people are used to simple regulated linear drivers, which just taper down the input voltage from the cell to the led when required. This happens when driver input voltage is higher than what is required by the led at whatever selected mode, to limit the output current to the one for the selected mode, and is âsensedâ by the driver. With these drivers you can just go turbo, high, medium, etc. without any difference in output if the cell voltage is very low, as the driver cannot boost voltage or create a sufficiently low load for the cell to deliver high or turbo power levels at low voltage.
With boost, boost/buck, or buck drivers in multi-cell configurations which guarantee that input voltage is always strictly higher than led or emitter voltage, the song changes. I have a few fully custom boost driver powered flashlights and I love them. When using them, if the cell is rather low in voltage I usually get a dim down warning or a straight low voltage warning if I switch to turbo. But as I said, this is the driver's behaviour.
A cell doesn't cares if you straight short it out with a thick copper wire, for example; you may see some sparks if done briefly to check it out and leave it there. But it's always better if you know what you are doing and its consequences, taking full responsibility of them, of course.
Sound and sage advice. Itâs not always cut and dry during usage, but personally, Iâve come to be rather dependant on the âbattery checkâ function in most of my oft used torches. Itâs one of the benefits of Anduril, and the bane of â12 modeâ or Biscotti type drivers due to the fact itâs not available on all modes. I routinely take my FWAA/H10 down to 3.1V, but I know from experience it is neither dangerous or detrimental to the cell other than the effect on ultimate lifespan, which for my cycle frequency is moot (2-3x year). That being said, for those cells installed in lights that donât accommodate âbattery checkâ functions, Iâm fairly religious about a DMM spec check if I suspect unloaded voltage is getting near nominal (3.6 â3.7). I usually terminate usage around that range more often than not because I have a rotation cell waiting to be charged/installed, and the depleted cell goes on vacation for a month or twoâŚ.Iâm not a slave driver by any means. Too many lights, too little darkness.
YMMV.
Henrikâs graphs plotted around 3.3 V no-load voltage (after a slight rest) for the cells tested. But if a cell is at 3.6 V no-load, it still has a perceptible amount of energy in it.
The no-load voltage of a cell after discharge is rather dependent on the discharge current. I once slow discharged a couple 18650 cells in parallel down to â2.5 V for a week, using cells already discharged down to â3.45 V to start with. I used a white led as the load, so the minimum discharge voltage was the ledâs Vf at the measly current which flowed at the end of the discharge period. After a week the led would barely be viewable even in full darkness, and I also I noticed that one of the cells was not really connected (it was all tied quickly with thin wires, copper sheet and magnets), so I properly reconnected everything and let it discharge for another week or so. After the test I could measure one of the cells slightly above 2.8 V, and the other was at 2.5 - 2.6 V. Of course it is easy to understand that the cell with more voltage was the one which initially got disconnected, and so it was discharged for a lesser amount of time. The cells were in parallel and it surprised me to find such large voltage difference between them after a week, so I guess there was some contact resistance doing its job somewhere. I may repeat this sort of test soon.
Some of you believe that leaving your cells at a somewhat low voltage will harm them in any way, but in my limited experience with li-ion cells I am still to see that. However, leaving them at high voltage results in voltage related stresses and this is proven to damage cells or reduce their cycle life considerably. This is the reason why laptop batteries which are kept fully charged at all times inside their devices endure short lifes even if not cycled, and I know this by experience.
