18650 battery super hot when charging - Page 1
Forum section: electronics / general

author: ElectricPower
author_rank: Frequent Contributor
timestamp: January 12, 2021, 05:58:58 am
content: I have an Xtar Dragon VP4 Plus Charger. I have some 18650 cells rescued from an old computer battery. I meassured 6 of the nine batteries to hold between 2.5 to 2.7V. Rest of the batteries was destroyed.When i perform an "Recycle" charge with Xtar charger i meassured the surface temperature on the batteries to be 82 degrees celcius. Too hot to touch. I just had to turn off the charger.Is that temperature normal?I meassured the internal resistance of batteries to be between 28 and 36 milli ohm.

author: Siwastaja
author_rank: Super Contributor
timestamp: January 12, 2021, 09:12:14 am
content: No!The cells are dangerous, do not use them.What was the charging current?How did you measure the internal resistance?

author: ElectricPower
author_rank: Frequent Contributor
timestamp: January 12, 2021, 10:27:55 am
content: Quote from: Siwastaja on January 12, 2021, 09:12:14 amCharging current was 1 amp. I measured resistance with Xtar's own probes that come with the charger.

author: TimNJ
author_rank: Super Contributor
timestamp: January 12, 2021, 02:29:41 pm
content: Even 2.5 - 2.7V means that the cell was allowed to discharge too low, or at least, the battery self-discharged if it was left in storage without periodic maintenance charge. I wouldn’t touch a cell under 2.75V.

author: PeteH
author_rank: Unknown
timestamp: January 12, 2021, 02:44:26 pm
content: Red Sanyo cells?

author: ElectricPower
author_rank: Frequent Contributor
timestamp: January 12, 2021, 02:50:38 pm
content: Quote from: PeteH on January 12, 2021, 02:44:26 pmRed yes. But it was no marking on the batteries at all.Her is the batteries.

author: ElectricPower
author_rank: Frequent Contributor
timestamp: January 12, 2021, 02:51:56 pm
content: But the TP4056 module allows voltage down to 2.5V?

author: tunk
author_rank: Super Contributor
timestamp: January 12, 2021, 03:15:21 pm
content: I've seen cells below 2V turn out ok.In this case with 82C, send them to recycling.Edit: 82C shows that there's something wrong,possibly with the charger. What's the cellvoltage after charging?Edit2: If you by "Recycle charge" mean to testthe cell capacities, then the charger has todissipate ~15W (4x1A*4V), which could explainthe temperature.

author: TimNJ
author_rank: Super Contributor
timestamp: January 12, 2021, 04:11:26 pm
content: Whether or not a cell can tolerate being discharged to 2.5V, signifying ~0% state of charge, is dependent on cell quality. With cells of unknown quality and/or health, I would consider these dead.

author: ElectricPower
author_rank: Frequent Contributor
timestamp: January 12, 2021, 04:48:51 pm
content: Quote from: tunk on January 12, 2021, 03:15:21 pmI stopped the charger when the battery prosent show 79%. Cell voltage after charging was 4.08V.A little strange thing is that the other two batteries i charged showed 4.400mA capacity after charging from empty. Too good to be true?I do not think it is problem with charger. But i do not know...

author: Doctorandus_P
author_rank: Super Contributor
timestamp: January 13, 2021, 07:43:24 pm
content: There are 100+ different chemistry variations for Li (-blabla) batteries, and they do not all work at the same voltage.If you salvage batteries from some battery pack, then those cells may work on a lower voltage.Your batteries may still be OK (but it's not good to let them get so hot). I've also got some of those red cells form an old laptop, and they work fine if you do not overcharge them (you're overcharging as soon as the start warming up). I think the max. voltage is around 4.1V for those cells.

author: mikerj
author_rank: Super Contributor
timestamp: January 13, 2021, 07:59:25 pm
content: Quote from: ElectricPower on January 12, 2021, 04:48:51 pmFar too high for a single cell. There are 3500mAh cells available now, but you won't find them an old laptop battery. 4400mAh is about double what I'd expect, is the charger connecting two cells in parallel?

author: Siwastaja
author_rank: Super Contributor
timestamp: January 14, 2021, 09:41:18 am
content: Put 2+2 together.1) Battery is exceptionally hot after charge2) Exceptionally high amount of charge went inWhat happened to that charge you put in?Mind, a good li-ion cell has near 100% coulombic efficiency, i.e., if you put 2000mAh in, you can extract 2000mAh out, and only the voltage difference causes energy to be converted to heat. But this may not be the case with broken cells. Extra chemical reactions can happen, consuming charge. Obviously, this is very dangerous.

author: ElectricPower
author_rank: Frequent Contributor
timestamp: January 14, 2021, 04:23:47 pm
content: I run an refresh for four old laptop batteries and the charger says the capacity is... just see the pictures. How can the charger show 3.800 mA?

author: Siwastaja
author_rank: Super Contributor
timestamp: January 14, 2021, 04:43:50 pm
content: Are you sure it isn't a sum of multiple cells?

author: tszaboo
author_rank: Super Contributor
timestamp: January 14, 2021, 05:04:33 pm
content: Quote from: ElectricPower on January 14, 2021, 04:23:47 pmBecause the battery has very high self discharge, so it is passively discharges itself, while being charged.The level a cell can hold charge is a better indicator of it's remaining useful lifetime, than ESR or measured capacity.Do yourself a favor, and dispose all these. You can buy new 18650 locally for around 3 EUR. Compare this with fire damage, or an eye injury. Do not place this into communal trash, stores that sell electronics equipment (usually) have to take back broken batteries.

author: Siwastaja
author_rank: Super Contributor
timestamp: January 15, 2021, 07:28:04 am
content: Or better yet, don't play around with these cells at all. You are not supposed to handle them, at all, they are for professionals who know what they are doing.This being said, at the bare minimum, follow the procedure for overdischarged cells: charge at VERY low current, say C/100, for an hour or so; if the voltage isn't rising, and if it's not holding after such charge, the cells are leaking (self-discharging) too much to be safe. Only after you have verified such C/100 charge gets them to normal voltage range (i.e., over 3.4V), and they stay there - you can rest them for a day, for example - only then commit charge at regular rate like C/2.

author: BravoV
author_rank: Super Contributor
timestamp: January 15, 2021, 07:37:57 am
content: Quote from: NANDBlog on January 14, 2021, 05:04:33 pm+1Also tips, try find locally if there are vaping communities, usually vape suppliers carry good quality 18650 cells, as these are also life style thing, pretty sure they have reputable brand ones, rather than buying abroad at unknown sellers.

author: DC1MC
author_rank: Super Contributor
timestamp: January 15, 2021, 08:21:00 am
content: Quote from: BravoV on January 15, 2021, 07:37:57 amWell, It could be less than a lifestyle choice but the fact that you keep them in your mouth while under load that they prefer hi-quality cells

author: BravoV
author_rank: Super Contributor
timestamp: January 15, 2021, 08:35:29 am
content: Quote from: DC1MC on January 15, 2021, 08:21:00 amLOL yeah, what I found out is locally, in the communities, as lifestyle things, usually they bragged about using quality cells like Panasonic, Sony, LG and etc, that is how I procured my 18650 cells.Few of my acquired 18650 and 14500 (AA sized) Panasonic and Samsung cells while ago locally from these crowds.

author: sleemanj
author_rank: Super Contributor
timestamp: January 15, 2021, 08:54:39 am
content: I would posit that there is something not right with your charger or you are using it incorrectly somehow.If you salvaged 18650s that had been sitting for who knows how many years and they still had a voltage of 2.5v, then they don't have that much self discharge, I would fully expect such cells to take and hold charge (but, I would bring them up slowly and safely of course!) and often have perfectly reasonable capacity, at least for use at low currents.Your charger seems really whacky in the numbers it's reporting (or it's just a bad confusing user interface) and dumping in so much current to a low voltage battery that it manages to heat up to such an appreciable degree... well.. that's not smart.A TP4056 starts low cells at 10% of the normal charge current, just 100mA for most modules by default. When I bring up old cells I use a 500mA configured TP4056 so it starts the trickle in process at just 50mA.

author: ConKbot
author_rank: Super Contributor
timestamp: January 27, 2021, 07:53:49 am
content: If your cell is at 82C case temp while charging, its done, dispose of it. Doesn't matter if it's internal or external heating both cases the cell is now damaged and a hazard.If it's external heating, throw away the charger too as no charger worth having would heat up enough to warm cells that much.Stop cycling them hoping it gets better, that's how you make them vent, maybe even with flame and clouds of fluorine containing compounds. 40-45C is usually the max temp acceptable while charging. Storage at 50-60C max. Charging at 82 is a significant fire/vent risk, and not just casual fearmongering.