Samsung cells popping and reading 200mV - Page 1
Forum section: electronics / beginners

author: avogadro
author_rank: Contributor
timestamp: March 10, 2020, 07:30:18 pm
content: I got this new eCig and it basically killed 4 of my samsung cells (INR21700-40T and US18650VTC5A). I dug through the datasheets and I cant find any mention of internal fuses or anything. They are basically labeled as unprotected. I measured them after they died and they are all showing 0.2V which is the voltage of a completely depleted cell. How does this even happen? They go from working fine to all of a sudden dead. Anyone had any experiences like this?

author: thm_w
author_rank: Super Contributor
timestamp: March 11, 2020, 12:00:26 am
content: Was that a single cell or were multiple in series?How much current do you think was flowing through them? Is there any way to measure the coil resistance, or is it too low.The battery is not physically cut on its insulation anywhere, resulting in short?

author: james_s
author_rank: Super Contributor
timestamp: March 11, 2020, 12:12:24 am
content: Virtually all li-ion cells are protected in that they are internally fused and will fail gracefully if they are short circuited. Cells that are sold as "protected" typically means they have auto-resetting electronic overload protection.Does your device work with any batteries? If not then it has a short that is killing batteries. If it works with some but pops others then it is drawing too much current for the particular cell type.

author: TimNJ
author_rank: Super Contributor
timestamp: March 14, 2020, 01:58:19 am
content: Lithium ion cells from virtually every manufacturer should include a CID which pops when there's sufficient gas build up in the cell. Usually this happens due to overcharging.https://www.nasa.gov/sites/default/files/files/345992main_NESCTB09-02_LiIonBatteryLimitations.pdf

author: wraper
author_rank: Unknown
timestamp: March 14, 2020, 02:23:26 am
content: Quote from: avogadro on March 10, 2020, 07:30:18 pmThe one which won't fail this gracefully may shoot fire and metal into your mouth. Most likely they died as internal pressure switch disconnected positive terminal. Using mech mods with "unprotected" cells is not very smart, more so one which kills batteries. You may find yourself with crippled face one day.

author: ogden
author_rank: Super Contributor
timestamp: March 14, 2020, 02:31:26 am
content: What about defect of eCig which led to overdischarge of the batteries? Just asking so "big heads" can think of this possibility and comment.

author: Psi
author_rank: Super Contributor
timestamp: March 14, 2020, 03:52:44 am
content: Quote from: avogadro on March 10, 2020, 07:30:18 pmYou could always take one apart and see what happened inside, since they are dead anyway.Just have to do it outside with safety glasses on and some fire proof gloves.If i had to guess i would say maybe your new e-Cig has a bad charging circuit and is overcharging them until the protection pops from too much gas production.We've all seen videos of crappy china products that have those charging circuits that are just a resistor to USB 5V

author: Siwastaja
author_rank: Super Contributor
timestamp: March 14, 2020, 09:14:39 am
content: They are "unprotected" in the sense of not having electronic circuitry, but have many levels of passive protection.They have resetting PTC fuses (that react to both overcurrent, and to some degree, overtemperature). They reset once cooled down, but do note that even one trip event permanently increases the resistance of the PTC element, causing more losses in the future (and lower trip threshold).In addition, they have CID or current interruption device, basically an overpressure valve which physically disconnects the load.Severe overcurrent (something that could be described as a short-circuit, or nearly so) is the likely cause.Sometimes overcurrent / short events do not permanently disable the cell, sometimes it can do that. It's better, IMHO, if the cell actually dies completely and does it quickly, and I would prefer single-blow fuses instead of the PTC self-resetting type.Note these cells arenotdesigned for consumers to use as-is, and even though they have quite decent safety mechanisms, those are the last layers of defence and not exactly 100% reliable.

author: Terry01
author_rank: Frequent Contributor
timestamp: March 14, 2020, 09:49:45 am
content: I can think of 2 different reasons I have came across as a long term "leccy smoke" user.The first I am not 100% sure exactly, but I remember when getting a sort of mid priced (£25) one, the guy told me not to use an iPhone charger or a couple others I can't remember because it would charge it too quick and would damage the battery.The other was a more expensive (£55) leccy smoke that had high current batteries, I was told not to use "normal" 18650's as they couldn't handle the "draw" and again, would be damaged.I am no expert though and this is just things I was told when buying new smokes.Hope this helps...