Same 18650 battery size, different voltages, how to avoid a catastrophe? - Page 1
Forum section: electronics / beginners

author: NaxFM
author_rank: Regular Contributor
timestamp: April 25, 2023, 05:58:08 pm
content: So, after many years i'm finally starting a project which involve the terrifying (according to media and shipping services) lithium battery. I identified a balancing IC and a charger IC that i like but when looking for 18650 batteries i noticed something that made me worrying: both LiIon and LiFePo are sold as 18650 cells.They have vastly different nominal and charging voltage, and now I have many doubts. What happens if I design a product to use 18650 LiIon cells and someone uses LiFePo cells instead? LiFePo cells have a much lower charging voltage (3.7 max) and it can get dangerous to go above that, especially at LiIon levels (4.2V). There is no way to detect which battery is being used, as the voltage depends on the charge level, so can't configure the charger and balancing circuit on the fly with some microcontroller, so what to do?One solution i could find is to design everything to use LifePo cells to maintain a safe voltage for both types, but this way i'm stuck with lower capacity and if someone uses LiPo cells i'm basically throwing away half of the capacity.Another solution would be to consider everything a LiFePo cell untill a full charge cycle where i can accurately measure the voltage curve, and with that detect the type of cells, but sounds quite complicate and prone to error...Am I missing something? I find very dangerous that 18650 cells of the same exact size can be so different. Granted they have integrated protection circuit to prevent overvoltage, but still...

author: tooki
author_rank: Super Contributor
timestamp: April 26, 2023, 07:03:34 am
content: 18650 cells were never intended to be user-accessible cells the way AA batteries were. You’ll observe that no name-brand product ever uses user-accessible 18650s — they invariably have the cells either sealed in the device, or the cells are assembled into a battery pack with safety circuitry built in.If you want to ensure users can only use the correct battery type, then use a battery pack with authentication IC. Or don’t give users easy access to the cells.

author: Siwastaja
author_rank: Super Contributor
timestamp: April 26, 2023, 07:18:14 am
content: Normal manufacturing quality control. Just don't buy the wrong stuff.Wait, are you implyingthe end userwould buy 18650 cells from any source and install them in your devices? A colossally bad idea! These are professional components, only to be used by professional customers. You have to design a protected battery pack like everybody else.

author: AndyBeez
author_rank: Frequent Contributor
timestamp: April 26, 2023, 08:30:15 am
content: First, use solder in situ tagged cells which are not implicitly user replaceable. Second, design with the correct charge controller chipset for your BMS. Third, secure the battery compartment with torx screws or glue. Forth, implement supply chain tracing and random teardown quality control checks on production batches. Fifth, stop worrying.

author: mikerj
author_rank: Super Contributor
timestamp: April 26, 2023, 02:14:02 pm
content: Lithium Iron Phosphate cells are pretty safe, overcharging is quite unlikely to cause catastrophic failure. There are videos on Youtube of LiFePo cells being grossly overcharged to 8v or even 10v and they do swell up or vent but none of them caught on fire.

author: Siwastaja
author_rank: Super Contributor
timestamp: April 26, 2023, 03:07:16 pm
content: Quote from: mikerj on April 26, 2023, 02:14:02 pmI have repeated the exact same test on feared LCO and NCA chemistries, except overcharged to 30V for hours. No swelling, no venting, no catching fire. On the other hand, I have seen too many reports of LFP cells catching fire when overcharged.Simply don't count on the safety ofanyli-ion chemistry when abused. It's completely false sense of security.

author: NaxFM
author_rank: Regular Contributor
timestamp: April 26, 2023, 06:06:56 pm
content: Thank you everyone for your answers. I can see why you say there are cases where batteries shouldn't be user replaceable, and i agree, up to a certain pointWhat I want to do is a very specific test gear aimed at professionals (If this turns up to be a viable product in the end), and I don't like that a professional must resort to the manufacturer to replace the batteries after a few years. I want my design to be open and user serviceable, after all we all love the old HP and Fluke service manuals with full schematics, theory of operation and part list, right?You may say "If it is aimed at professionals, they should know what type of battery to use", and I totally agree. Still, since batteries are a topic that scares me a bit, i don't want to take any chances and trust whoever could end up servicing the product.This is also the reason why I want to use simple plain 18650 cells and not some sort of pre-built battery pack: the user should be able to change batteries without any kind of arficial obstacle.

author: Jwillis
author_rank: Super Contributor
timestamp: April 26, 2023, 06:55:20 pm
content: Here's a video that is interesting to watch. Unfortunately it doesn't include Lithium Ion .

author: David Hess
author_rank: Super Contributor
timestamp: April 27, 2023, 06:32:51 am
content: Quote from: tooki on April 26, 2023, 07:03:34 amUser accessible 18650 cells are very common in tactical flashlights, most of which will also accept two CR123A cells in series as an alternative.

author: Siwastaja
author_rank: Super Contributor
timestamp: April 27, 2023, 08:03:19 am
content: The fact that some manufacturers of consumer products (e-cigarettes, flashlights) have went on user-replaceable 18650 cells does not mean it's correct. The situation is a total mess, because the cells were never meant to be replaced by user. They are designed to be spot-welded into battery packs by battery pack manufacturer, period. So-called "protected" cells made the mess even messier.No one is physically preventing you from playing the same game. Obviously, such products are constantly being recalled by authorities as they constantly cause issues like fires, so I suggest you should operate from China and hide your tracks very well so that you won't be personally responsible when someone dies because of your product (this is how those flashlight / e-cig manufacturers operate; importers handle the business risk).Quite seriously, if you want to design a battery operated product with user replaceable batteries, what you need to do is to find a reliable source of truly genuine brand 18650 cells, get a spot welder, design your BMS properly, and get someone to design a plastic casing (3D printing works for small batches).

author: Doctorandus_P
author_rank: Super Contributor
timestamp: April 27, 2023, 08:28:03 am
content: Designing your product to be compatible with both chemistries has extra complications, especially when you have a built-in charger. Just pick one type that suits your use case best. Do you want the high energy density of Li-ion, or the extra safety of LiFePo?Exchanging batteries with spot welded solder lips is not difficult for a "qualified technician" (Presuming they can open the case to get to them, the battery is nog glued, etc). Soldering the batteries instead of some spring loaded battery holder also has some extra reliability.It also helps if you clearly mark on your product (PCB silkscreen?) what type of battery is being used, and the polarity, especially if there is a chance your product can get stored for some time without the batteries.That should be enough. Anyone working with those batteries should know the differences and that they are not interchangeable. If you still believe you can make your product idiot proof, then you have underestimated the ingenuity of a true idiot.

author: tooki
author_rank: Super Contributor
timestamp: April 27, 2023, 09:44:33 am
content: Quote from: David Hess on April 27, 2023, 06:32:51 amI know it’s common in those flashlights, and in vape devices. But it was never the battery industry’s intent, and they invariably state in their datasheets that the batteries are not intended to be user-accessible.

author: tooki
author_rank: Super Contributor
timestamp: April 27, 2023, 10:03:21 am
content: Quote from: NaxFM on April 26, 2023, 06:06:56 pmHere are the things you have to consider when doing that:1. You have to provide some user-accessible way to set the charging parameters, because they are NOT the same from battery to battery,even within the same chemistry. You have to be able to set the charge current, cutoff voltage, cutoff current, and undervoltage cutout at minimum. For example, the cutoff voltage needs to be set to within 50mV, so you can’t just select a “typical” voltage.2. What is the legal liability? Are you making yourself liable if someone puts in the wrong battery type and it then gets damaged? Or what if someone changes the charging parameters for the battery you shipped in it, and it gets damaged? What if someone inserts damaged batteries? What if any of those things causes a fire? What if somebody gets killed in such a fire?Don’t underestimate all this. In a battery board I designed, I had an incident where a cell had somehow had its plastic sleeve damaged the tiniest bit. When I inserted it, that pinhole made contact with the battery terminal, a dead short that caused the battery terminal to glow red hot within 3 seconds. Even with tools around me so that I could lever out the battery practically immediately, the battery ended up spewing electrolyte. (No fire, luckily.)There are very sound reasons manufacturers put in “artificial obstacles” to LiIion cell access. If you want to provide a user-replaceable battery pack, provide the cell parameters and whatnot, but sell the pack yourself at reasonable cost. Or use a common type of battery pack (for example, a Sony camera battery, a power tool battery pack, or even a broadcast video battery pack (Anton Bauer style), since those are completely standardized).

author: Siwastaja
author_rank: Super Contributor
timestamp: April 27, 2023, 10:21:50 am
content: Quote from: tooki on April 27, 2023, 10:03:21 amYes, this is one of the biggest risks IMHO in using user replaceable 18650 cells. Heck, it's a risk item even in factory manufactured packs, the nickel strips to be spot welded have sharp edges and there are incidents they have penetrated the thin plastic near the positive terminal, shorting the positive strip to the 18650 metal case, which acts completely as the negative terminal. Battery pack manufacturers nowadays use extra insulating donuts (sometimes self-adhesive) to avoid this incident type.For an unauthorized end user, the situation is much more dire because of accumulating mechanical damage to the thin plastic, especially if "slid" in place to a holder. So called "protected" cells are inherently susceptible, on their own, as the protection PCB has to connect to both terminals so they use a thin strip of metal crossing the thin plastic sleeve. Protected cells are therefore known to blow up on their own. There is no legitimate use for a "protected cell" IMHO, the whole concept is trying to fix unauthorized crap by adding more unauthorized crap on the top of it.

author: David Hess
author_rank: Super Contributor
timestamp: April 27, 2023, 11:41:01 am
content: Quote from: tooki on April 27, 2023, 09:44:33 amIt was industry who dropped the ball because there was no safe consumer alternative. It may be the case that there could never be one because of the economics, but see below about CR123A cells.Quote from: Siwastaja on April 27, 2023, 08:03:19 amMost, or even all, of the fires I have seen were caused by series connected CR123A cells which *were* intended to be user replaceable. Again industry dropped the ball because there was no way to distinguish primary from secondary CR123A cells, and if it was a problem, then there should have been an alternative, which is what the 18650 became.You might remember that this came up long ago with rechargeable NiCd AA cells with primary cells having a narrow button and secondary cells having a wide button, but this only resulted in more problems.QuoteYet when manufacturers do that, invariably it is used as a form of lock-in to extract rents. A larger problem is that the battery situation encourages manufacturers to prevent user replacement of batteries at all, resulting in more electronic waste, however this is just a side effect of using battery lock-in to implement enforced obsolescence. Evidence of this can be found in manufacturers not even making safe replacement batteries available, even for products which have user replaceable batteries like my smartphone.I wanted to use LiFePO4 18650 cells with my flashlights, but have not been able to find any.

author: tooki
author_rank: Super Contributor
timestamp: April 27, 2023, 01:06:35 pm
content: Quote from: David Hess on April 27, 2023, 11:41:01 amOr maybe the problem is that bare extremely high-current cells, like LiIon, simply can’t be made safe enough to be considered consumer products. Combined with their princess-and-the-pea charging needs, it simply makes sense from a safety and liability standpoint to offer consumers battery packs, not bare cells.Quote from: David Hess on April 27, 2023, 11:41:01 amWhat you’ve seen is not representative. The fact is that there have been countless reports of injury from LiIon cells in vaping devices, which are designed around 18650s because of the high currents they can deliver. I am quite certain the battery manufacturers don’t like seeing vaping devices sold with not only removable cells, but with external chargers, causing users to keep bare, charged 18650s I’m their pockets as spares.As Siwastaja said, such devices keep getting recalled, but there’s always a new vendor putting that same crap on the market.Quote from: David Hess on April 27, 2023, 11:41:01 amI gave you multiple examples of manufacturer-independent battery pack standards: broadcast video (which has one or two standard battery types; when you buy a broadcast camera, it has a mount for a “battery plate” which has the attachment for the battery standard your organization already uses, for example the common “v-mount” battery. Your cameras, recorders, screens, audio gear… it all uses the same batteries. 12V DC IIRC.). The other major one I listed was power tools: for a few years now there’s been a standard, the Cordless Alliance System, for standardized power tool batteries. A few major manufacturers are using it, as well as a ton of smaller ones. That pretty much ensuressomebodywill be making compatible packs for ages.Also, the Sony camcorder batteries I mentioned are similar: Sony developed the format, but it’s since been adopted by many manufacturers of other devices, including compatible batteries. So they too will remain available for a long, long time.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: April 27, 2023, 02:57:06 pm
content: Quote from: AndyBeez on April 26, 2023, 08:30:15 amAgree with all the cautions in prior posts, but if you feel compelled to proceed with user replaceable cells the above quote, modified in red is a good start. I would add, since in spite of all that there will be folks who will do replacement, you should add documentation both in user manual and inside the unit on the ONLY acceptable battery chemistry for replacement and also legal warning about ending warranty and legal liability if any user maintenance is performed.

author: David Hess
author_rank: Super Contributor
timestamp: April 27, 2023, 09:30:11 pm
content: Quote from: tooki on April 27, 2023, 01:06:35 pmThat is not a new thing. I have had several fires with NiCd batteries. It was not the batteries which caught on fire, but the wiring.

author: tooki
author_rank: Super Contributor
timestamp: April 28, 2023, 12:02:14 pm
content: Quote from: David Hess on April 27, 2023, 09:30:11 pm…aaaand? How does that invalidate any part of what I said?

author: Siwastaja
author_rank: Super Contributor
timestamp: April 28, 2023, 03:19:03 pm
content: Protecting wiring against fire is trivial withthe wiring protection component, also known asfuse.

author: David Hess
author_rank: Super Contributor
timestamp: April 28, 2023, 10:20:50 pm
content: Quote from: tooki on April 28, 2023, 12:02:14 pmIt is neither a new problem, nor a problem only with modern lithium battery chemistries.Quote from: Siwastaja on April 28, 2023, 03:19:03 pmThe fuse has to be located somewhere leaving some of the wiring unprotected.

author: tooki
author_rank: Super Contributor
timestamp: April 29, 2023, 02:03:24 pm
content: Quote from: David Hess on April 28, 2023, 10:20:50 pmAnd who said it was a new problem? I don't see anywhere that I made that claim.While bare rechargeable NiCd cells were available in the past, they weren't particularly popular, people weren't using them in vape devices, and most products used NiCd cells in packs, not loose.The only rechargeable products I've ever seen that use user-accessible, standard-size, loose rechargeable cells (not battery packs) are cordless phones using NiMH cells. Every product with NiCd that I have ever seen used either custom cells (like the early gumstick batteries in some old Walkmans, before they switched to NiMH) or battery packs. Is there such a product out there somewhere? Probably. Doesn't mean it was a good idea then, either.Quote from: David Hess on April 28, 2023, 10:20:50 pmSo... use insulated wire of adequate gauge for all of the wire before the fuse?I think the rest of us are struggling to envision the problem you have in mind. Can you give an example?

author: David Hess
author_rank: Super Contributor
timestamp: April 30, 2023, 11:07:13 am
content: Quote from: tooki on April 29, 2023, 02:03:24 pmThe products were anything where an end user might use rechargable NiCd cells in place of the intended alkaline cells, like my calculator, my flashlight, my remote control toy car, my portable cassette player, etc. My retired cordless phone is the only thing I have seen that came with loose AAA NiMH cells, but that was only a few years ago.I have a whole collection of AA and AAA Eneloop cells for various things. If there were Eneloop 9 volt batteries, then I would have some of those also for my multimeters. Nothing I use them in was intended to use rechargable cells.QuoteSometimes a wire inadvertently gets pinched, but like modern lithium cells, the insulating sleeve around the battery could be abraded, or I saw one time where a left over cut lead fell into the battery area and shorted across the terminals. Does anybody remember metal battery holders from companies like Keystone?The point is that NiCd cells can also be a fire hazard under short conditions, so this is not a new hazard and it was something to be aware of before lithium batteries became available. At least NiCd cells were not combustible in of themselves.Primary CR123A cells have been generally available for a while, but I noticed yesterday that specialty stores now carry larger secondary lithium cells in bubble packages.I never did find a source for LiFePO4 CR123A or 18650 cells that I trusted, but perhaps that is because of ongoing supply issues.

author: AndyBeez
author_rank: Frequent Contributor
timestamp: April 30, 2023, 11:56:10 am
content: Quote from: David Hess on April 30, 2023, 11:07:13 amThe real issue for design engineers; supply chain trust. Even in a large electronics company with a procurement department and inspection stations all of the way down the line, production needs to be able to be confident that these parts are 100% to specification in the first place - and not just because someone says they are "genuine" or "authentic". Which is why those parts cost money direct from the manufacturer who also, has a chain of trust with their suppliers. But when it comes to profitability, confidence is an easy element to remove from the cost base.As the OP has decided to make the product withuser serviceable parts inside, this adds the supply chain trust of who ever, when ever, is swapping out the batteries for new ones. So these guys are anticipated 'certified professionals', but you can guarantee there will be someone who does not know their AC from their DC, let alone a vape battery from a fake-vape battery.I noted the other week a local college is training car mechanics to service EV car batteries - by training them how to use a voltage meter to find defective cells. I hope they teach them what a certificate of conformance is and, how to source the correct replacement cells. As if a regular garage is going to go to that expense?Could the OP just use AA batteries instead?

author: artag
author_rank: Super Contributor
timestamp: April 30, 2023, 07:42:33 pm
content: Quote from: David Hess on April 27, 2023, 11:41:01 amI have found quite a few sellers on Alibaba. MOQs may be larger than you want. On aliexpress I could find vendors of 32700 and 28650 LiFePO4 but not (or maybe just one) 18650. This could be because LiFePO4 18650 are typically only 1.5Ah whereas LiIon are 3.1Ah or higher. maybe it's not really worth making the smaller cells.I also found it odd that Li-Ion are frequently available tagged but all the LiFePO4 I found were untagged.I have a need for low production quantities of LiFePO4 in some size around 18650 (OK if bigger but not the larger square cells). I'd be glad of a recommendation for a reputable source.

author: amyk
author_rank: Super Contributor
timestamp: April 30, 2023, 07:51:25 pm
content: Playing "spot the industry shills" in this thread is far too easy...But seriously, all you need to do is specify the required battery type clearly. It's not your problem anymore after that if some idiot decides to put the wrong one in. I'd not choose phosphate unless there's a special need for that type, as they are more rare. Regular 4.2V lion is far more widely available.

author: westfw
author_rank: Super Contributor
timestamp: April 30, 2023, 09:37:01 pm
content: QuoteCan't you check the charge current at the end of the of the LiFePO4 charge cycle? Ie, if you you set the charge voltage to 3.7V and have an LiFePO4 cell, it'll be fully charged and in "trickle" mode by the time cell voltage reaches 3.7V, but a normal LiIon cell will still be drawing significant current...

author: westfw
author_rank: Super Contributor
timestamp: May 01, 2023, 12:51:00 am
content: QuoteBut if you apply 3.7V with a 500mA current limit to a 3.2V LFP, it will draw 500mA *until* it approaches full charge, at which point current would die off, but the LiIon cell would still be drawing close to 500mA.

author: tooki
author_rank: Super Contributor
timestamp: May 01, 2023, 08:56:47 am
content: Quote from: David Hess on April 30, 2023, 11:07:13 amBut I did not say “devices that NiCd batteries can be used in”, I explicitly saidrechargeable products, that is, products where rechargeable batteries are theintendedpower source. My point being that manufacturers of products intended to be used primarily or exclusively with rechargeable batteries rarely, if ever, designed them to use loose NiCd cells.Quote from: David Hess on April 30, 2023, 11:07:13 amPutting loose cells into something designed for alkaline cells is expressly outside the scope of my claim.Quote from: David Hess on April 30, 2023, 11:07:13 amSometimes a wire inadvertently gets pinched, but like modern lithium cells, the insulating sleeve around the battery could be abraded, or I saw one time where a left over cut lead fell into the battery area and shorted across the terminals. Does anybody remember metal battery holders from companies like Keystone?So… poor battery pack design or abuse.Not theQuote from: David Hess on April 28, 2023, 10:20:50 pmto which I was responding. That statement implies that it isunavoidableto have exposed wire.Meanwhile, risk of cell sleeve damage is likely one of the exact reasons that bare LiIon cells aren’t intended for consumer use, and the reason that product engineers of LiIonand NiCdrechargeable devices either build the cells into the device itself, or into a battery pack that has a lot more insulation or even a hard shell.Quote from: David Hess on April 30, 2023, 11:07:13 amNobody said it was a NEW hazard!! We are just saying that it IS a hazard. And LiIon’s own flammability is precisely why they’re so much more hazardous.You keep arguing based on thingsI did not say, and then ignoring things I did say. Cut it out, man.

author: tooki
author_rank: Super Contributor
timestamp: May 01, 2023, 09:06:40 am
content: Quote from: amyk on April 30, 2023, 07:51:25 pmI don’t think anyone here is an industry insider. (And referring to people as “shills” is just cheap pot shots, typically used by ignoramuses.)Quote from: amyk on April 30, 2023, 07:51:25 pmHah, how naive are you? Product liability is a serious concern. You have to design products around what people are likely to do, and fine print cannot definitively absolve you of that. (Various laws cover such things, and you cannot EULA yourself away from that.) And a key consideration is, as a manufacturer do you really want to test that theory in court? Do you want to spend hundreds of thousands, maybe millions of dollars defending yourself in court if someone dies? What will that do to your company’s reputation?Heck, even the mereaccusationcan ruin your reputation, even if you win. Major companies (like Samsung) have had to perform major damage control in the past when there were reports of their devices, like phones or cameras, catching fire in people’s pockets, even after it was determined that cheap third-party batteries were to blame!

author: tooki
author_rank: Super Contributor
timestamp: May 01, 2023, 09:15:44 am
content: Quote from: karpouzi9 on April 30, 2023, 08:03:30 pmThermal monitoring is considered a baseline safety feature for practically any LiIon/LiPo system. Only very small packs do without.But like the battery protection (over-/undervoltage cutoff, overcurrent cutoff) chips used on rechargeable lithium, that’s considered a “backup”, it’s not intended to be a primary charging limiter like you’d be using it as. The primary cutoff is supposed to be a properly configured charging algorithm.Note also that safety isn’t the only reason for wanting proper, accurate charging parameters: even if you are within what’ssafefor the non-identical replacement cell, that might not be what’sgood for it, resulting in reduced cell lifespan.

author: westfw
author_rank: Super Contributor
timestamp: May 03, 2023, 11:19:30 pm
content: QuoteFair enough. I was assuming that LiFePO4 cells had a charging profile similar to LiIon, but with a lower termination voltage. Apparently that's not the case, and the LFP profile is closer to "constant current" throughout. :-(With my original (incorrect) assumption, if you put 3.0V (discharged) cells into a charger at constant current (voltage setting doesn't actually matter during the constant-current phase) then by the time the cell voltage reached 3.7V the LFP cells would be fully charged and drawing minimal current, while the LiIon cells would still be in their constant current phase and drawing significant current. It's a shame that's not the case :-(QuoteDoes that happen after charging, or only when you start to discharge the cell? And how gradually is "gradually"?Either way, this seems like a "detectable behavior" for a sufficiently intelligent charger. A LiIon cell charged to 3.7V will remain at approximately 3.7V for quite a while; an LFP cell won't.OTOH, having done a bit more research, it seems that many sites claim that it is safe to charge LFP cells to 4.2V, in essentially a "constant-current only" cycle. They don't say what effect this might have on cell life, if any.OTTH, the web info on LiFePO4 seems to be relatively polluted with people selling 12V and 24V "lead acid replacement" batteries, happy to claim that you can just throw one into your car or into your solar system, and have it work with the standard lead-acid charging electronics.

author: KE5FX
author_rank: Super Contributor
timestamp: May 04, 2023, 12:08:29 am
content: Quote from: NaxFM on April 25, 2023, 05:58:08 pmWould it make sense to consider 14500 LiFePO4 cells, like the ones that Tenergy used to sell as the 30225? Looks like similar partsare sold by DigiKeyfrom a company called Ultralast. Unlike 18650s these are intended for consumer use, specifically in outdoor path lighting.The scary thing aboutthesebatteries, and probably the reason why they haven't really caught on, is that they are virtually identical in size to AA primary cells. They have both the voltage and the current-delivery capacity to utterly destroy almost any AA-powered device that an unwitting consumer plugs them into.There are also AA and AAA NiMH cells, which are very widely sold over the counter here in the US. I've used quite a few of them in isolation amplifiers and other gadgets built into Hammond boxes that I keep around the workbench. They offer a good combination of low self-discharge (similar to Eneloops, which have always been famous for that) and capacity, but aren't competitive with lithium of course.Failing all those ideas, I'd vote for tooki's suggestion of using a pack form factor that's already been semi-standardized in other industries.

author: james_s
author_rank: Super Contributor
timestamp: May 04, 2023, 02:32:20 am
content: Quote from: westfw on May 01, 2023, 12:51:00 amThe current dies off because the output voltage of the charger is limited according to the cell chemistry. If you connect a 3.7V LiFE cell to a 4.2V Li-ion charger the cell will happily charge right up to 4.2V, if it doesn't catch fire or trip the internal safety first. With most battery types the cell voltage is inherently limited but that isn't the case with lithium ion chemistries, or if it is, it's above the voltage at which the cell will destroy itself. You can't trickle charge a lithium ion battery with a constant current source, it will keep right on charging beyond the maximum cell voltage.

author: tooki
author_rank: Super Contributor
timestamp: May 04, 2023, 12:02:48 pm
content: Quote from: karpouzi9 on May 04, 2023, 01:26:14 amThat’s literally what a constant-current supply is. There can always be only one limitactingat a given moment, whether you’ve configured both or just one of the two. Only a conceptual ideal current source has infinite voltage available. In reality, the supply voltagealwayshas a maximum. The maximum voltage of a constant-current power supply is know as the “compliance voltage”. Your constant-current output voltage will never exceed your compliance voltage because that’s all you have available.

author: David Hess
author_rank: Super Contributor
timestamp: May 05, 2023, 12:04:39 pm
content: Speaking of catastrophe:https://youtu.be/qJ8BzvbeRXQ?t=155

author: amyk
author_rank: Super Contributor
timestamp: May 06, 2023, 03:47:57 am
content: Quote from: tooki on May 01, 2023, 09:06:40 amYou sure do sound like one. The same as the anti-right-to-repair authoritarians who spread fear and paranoia because it's against their greedy $$$ interests.Quote from: tooki on May 01, 2023, 09:06:40 amThere's a lot of lawyer-trolling, but we also have something called personal responsibility here. It's not "fine print" if it's clearly stated.Quote from: tooki on May 01, 2023, 09:06:40 amLet's not forget that one of the biggest widespread reports of fires with phones was withSamsung's own batteries.

author: bdunham7
author_rank: Super Contributor
timestamp: May 06, 2023, 04:15:39 am
content: Quote from: David Hess on April 30, 2023, 11:07:13 amI've had NiCd power tool batteries catch fire while in use for no particular reason. Someone I know in the aviation business went to work one morning to fly a plane that used a NiCd battery pack instead of LA and found the battery pack on the ramp under the plane, smoking and melting the asphalt. For some reason it had warmed itself up enough to melt out of it's case and continued all the way through the body of the airplane, leaving a set of smoking holes in the fuselage.

author: tooki
author_rank: Super Contributor
timestamp: May 06, 2023, 11:45:37 am
content: Quote from: amyk on May 06, 2023, 03:47:57 amI have never worked for a battery company or anything related. In fact I’ve only just entered the electronics industryprofessionallyvery recently.I just take safety seriously, that’s all.Let’s swap the order of the next two points.Quote from: amyk on May 06, 2023, 03:47:57 amI know that, and it cost thembillionsof dollars. But there were also issues with older Samsung phones with removable batteries, where phones caught fire with third party batteries — many of which were unknowingly bought by users who thought they were buying genuine ones, but got counterfeits instead.Quote from: amyk on May 06, 2023, 03:47:57 amBut I’m not a lawyer (though I did take a basic business law class in college). And it’s not “trolling” just because it’s something you don’t want to hear!You literally just provided an example of product liability causing a multibillion-dollar product recall.You can state all kinds of things, but that doesn’t necessarily make them legally binding. There are safety regulations for consumer products, and you cannot evade those simply by stating exceptions. A core tenet of contract law is that any clauses that have to do with illegal things are not binding. That’s why you can’t escape a murder conviction just because the other person stated in writing that they wanted you to kill them.The salient point here is this: You can have a signed liability waiver that says you’re not liable even in cases of gross negligence, but since gross negligence is a crime, that clause is unenforceable, so the other party can still take you to court for gross negligence. And since what constitutes “gross” negligence is quite fuzzy, allowing the use of incompatible batteriescouldbe found to be grossly negligent by a court or jury. As a company, do you want to take that risk?And what about your insurance company? The fine print in your liability insurance policy could very well require a duty of care, and if something happened and it was shown that you knew about a potential risk, but downplayed it or thought you could just weasel your way out of it with a waiver, the insurer may decide to deny your claim, leavingyouon the hook for damages.

author: james_s
author_rank: Super Contributor
timestamp: May 06, 2023, 06:19:34 pm
content: Quote from: amyk on May 06, 2023, 03:47:57 amWouldn't that be nice? Unfortunately the fact that you (and I) think that personal responsibility should be prevalent doesn't make it so. There are countless cases of people doing stupid things, somebody getting hurt, and then somebody else getting sued for not doing more to prevent that from happening.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: May 06, 2023, 06:36:37 pm
content: And of course, stupid is the brother of ignorant, and often combined in the same person, and mixed with just enough slyness to deny any form of responsibility.