FWIW I found the report's summary (a few days ago when this was also discussed) essential for clarifying for me what the linked "article" was talking about regarding "anode overhang" and "edge alignment".
To summarize it myself, the battery is cylindrically wrapped sheets of anode/cathode material, and you want the top edge to have a straight line consistently having the anode layers (|) sticking out beyond the cathode layers ()
edit: Welp, the unicode I illustrated with got stripped out; so trying again with pipes
anode
cathode
a a
c c
| | |
||||||
The pics with red and blue dots didn't immediately make this obvious to me, but made sense once I understood the "overhang" meaning.
I seem to recall this being a factor in the Samsung Galaxy Note 7 battery fire debacle. The article linked below has an xray image where you can see the anode/cathode overhanging and then being shorted by subsequent damage.
That was my general sense. And that "nominal" is really easy to identify visually with a (relatively slow) scan. I'd guess that means it's a clear quality control thing you (i.e. battery pack makers who are buying the cells) can expect the better manufacturers to do, and pay a slight premium for.
I'm not sure who is in charge of advertising at lumafield but in the last few weeks I've seen James Hoffman use lumafield CR scans on coffee pucks, Jeff Geerling use them on a Pi 500+, and now this. I'm probably not their target market but I definitely know who they are now.
It's pretty smart, IMO. They are targeting the nerds watching tech videos in their offtime. That's a great way to plant their name into the heads of said nerds when the boss decides they need a CT scanner for whatever reason.
Summary Statement: He summarizes the results of the "sabotaging" attempts by saying, "we just couldn't for the life of ourselves get a nonprotected modern lithium battery to do anything" [02:40:27], in terms of causing a fire. (referring to 18650s)
There are certainly problems out there with cells but it was a surprising statement from someone with a ton of real-world experience. Also they are a very conscientious company so they don't deal with dodgy stuff if they can avoid it.
Unfortunately, for products with batteries in non-standard form factors, we rarely have a choice of a manufacturer. For example, with home robot vacuums, we can only hope that brands will use top quality cells, but the information what cells are used is not even available to the customer. My Neato vacuum still runs great, but now that the company is out of business, my only battery replacement options are from no-name brands, with zero visibility of what cells are used internally.
> For example, with home robot vacuums, we can only hope that brands will use top quality cells, but the information what cells are used is not even available to the customer.
Hardware used to come with diagrams & schematics, for self-service and repair. This was a courtesy, but I guess manufacturers figured out it's better to make the consumer buy a new model. (AKA part of the reason why Commodore went bankrupt.)
Meanwhile we've been talking and implementing measures such as lists of ingredients and nutrients in food, SBOMs in software, privacy/tracking transparency, etc. Let's push it a little further.
You also have the option of building your own battery pack for these, or to disassemble an existing pack and replacing the cells. How difficult that is depends on the manufacturer, but from a quick look at the Neato packs I see it looks relatively trivial.
I'm in the process of replacing the battery in my old robot vacuum right now, and for the amount of time spent doing that, I could buy a whole new vacuum. It's a pity, because the battery itself can be replaced just by plugging it in, but all the batteries I could find were AliExpress fakes, so my two options are either "more e-waste" or "spend $500 in time doing it myself".
Some of us enjoy fixing things like these over and above the hypothetically fungible billable hour, and whether you can substitute some time in an evening with a billable hour or three is highly dependent on your employment situation.
But in this case the relevant cost under discussion isn't that of a replacement vacuum cleaner, but what value you assign to your house not burning down due to a crappy 18650 cell, or the anxiety of worrying that that'll happen.
Unfortunately the cheap "fatbikes" every kid has here these days have no premium cells and even worse chargers and usually poor or no balancing in the BMS. I don't expect them to not catch fire and my HOA is considering to ban charging ebikes in the basement (where you put your bike) due to that. End result is likely that people with more expensive bikes and cells adhere to this and charge in the house while the cheap ass bikes will still be charged in the basement and the fire department can flood it once again when it all goes up in flames.
I have one in 21700 and it seems a great battery so far. Otherwise I'm a Panasonic guy.
I ask because it sits on my forehead, inside a headlamp. Having my hands tied, addressing a problem quickly might be difficult. And them rascals get toasty fast when they ignite.
Molicel is top tier - their P50B is the best 21700 cell available on the open market. Eve, BAK and Ampace also make some really good stuff, although they can't match the performance of Molicel.
I came to the same conclusion when upgrading from 18650s to 21700s, I spent a long time trying to weed out the poorly binned rewards, and the minefield of lithium batteries. They weren't cheap but have been happy with their performance.
There are a lot of people out there that see 18650 or 21700 and think a lithium ion battery is a lithium ion battery and they're all the same (i.e. trying to pull 20 amps from a 2 amp peak battery). I miss one of the father's of liion battery education, Mooch (from ecigarettes forum) who had a whole methodology of testing, and educating people.
I've seen other videos of people driving nails into 18650s and "spicy pillow" square cells, and most of them didn't even let off a puff of smoke. What the vaping community was doing 10-15 years ago to launch batteries into the ceiling is beyond me.
Your best predictor of cell failure is brand + where you sourced it. Good brand cells sourced through a reliable channel are pretty much impossible to get a failure out of without gross abuse of the cells.
But far more dangerous than single cell failure is pack failure and there the quality of the welding and the balance wires is probably a much bigger factor than bad quality cells. You can easily create a nice looking bomb from grade A cells, and even manufacturers with good name recognition will mess this up from time to time.
So buy packs made with quality cells and ensure that whoever makes the pack has proper welding gear and QA in place to avoid surprises. Never ever use cells without a BMS unless they are in a 1S configuration.
> So buy packs made with quality cells and ensure that whoever makes the pack has proper welding gear and QA in place to avoid surprises. Never ever use cells without a BMS unless they are in a 1S configuration.
How do you put that advice into action? When I'm in an electronics store, they don't typically let you look at the welds inside each battery bank. (And if they did, I have no idea what I'd be looking out for.)
Good point. It requires disassembly, and if you're not comfortable with that it is a lot harder to get a good idea on this. But there are plenty of videos and photos online of various disassembled packs from high volume manufacturers.
Quality cells are a relatively small group of brands so that should be easy enough to check for, and you'll know looking at just one side of a cell group whether or not it was put together half decently or whether it is messy.
Stuff to look for: loose balance wires, bad welds (welds that don't penetrate so they're loose), pointy edges of connecting strips that touch the plastic insulation of the cells, insufficient spacing between the cells, insufficient insulation near the welds.
For one-off purchases this won't help, but if you are a reseller or larger purchaser then it definitely is a good idea to tear down a pack and inspect.
Cells are subject to aggressive binning – akin to the early days of MOS process. And specs and process capability adhesion in the industry are not as "serious" as they are in the modern, U.S.-led semiconductor industry.
Source: I work on 100% Si anode batteries constructed in part with a litho-derived laser process at Enovix.
Last time I checked, most manufacturing of semiconductors isn't done in the US... sure, they are leading in design, but the manufacturing is elsewhere.
Just a few days ago the apartment above ours burned down alledegly because of an explosion of an ebike battery. They left it charging overnight and exploded in the morning. Fortunately nobody got hurt, but it was really scary experience.
Extremely large currents and a race to the bottom price (despite lithium-ion being expensive, people are eager to get “value” for the money which rewards conpanies which cut corners).
I find their table of advertised vs actual capacity to be misleadingly negative. They only discharged to 3v. 2.7 could be viewed as more standard. 2.5 is not unheard of. For example, the vapvell 4000 they said was around 3000. They even have a note that says that isn't a reasonable capacity estimate. And yet they still put the percentage and the number. As if they've falsely advertised. However, if you go to vapcell's graphs on their website, it all tracks. Feels out of scope for the report and shouldn't have been done
I went to vapcell's website, looked at their charts and specifications. I disagree with your assessment.
They specify 3800mAh minimum discharge at 0.2C for their 4000mAh cell. They don't show a discharge curve at 0.2C in their charts (would be 0.8A) but they do have a 1A discharge. When the 1A discharge curve reaches 3V, the energy discharged is right around 3800mAh.
Lumafield discharged at 0.2C, and they saw only 3055mAh.
Vapcell's site mostly shows high current discharge curves, where yes there is more capacity below 3V available, but with Li-ion at lower currents, the curve is very steep past 3V, not much more capacity left after that. And when you're discharging at high current you won't expect to get the full capacity, anyway.
I'll also take this time to point out lygte-info which is a treasure trove of battery tests.
It even says "Conservative discharge that would not
extract maximum performance". A lot of electronics built for li-ion will not work <3V so it's a perfectly reasonable benchmark, especially to show the difference between brands.
Battery operated devices, while nominally 3.3V, commonly work down to 3V or even 2.7V in line with the voltage curve of lithium (not li-ion) coin batteries.
How do you even drain a 3.7V lithium ion battery below 3.3V? My devices that use 18650s will not let them go below that. Is it 3.3V nominal and the actual voltage is lower, like how they’re 4.2V fully charged?
I guess leave them sitting in a laptop in a barn for a few years. I was given some old shit gateway the other day, tried to charge it, no dice. Ripped the pack apart to find samsung 18650's with approx 0.7V voltage.
Against ALL recommendations I put these cells into a MC3000 and they charged up just fine to 4.2V. It does a 0.15A charge per cell until it gets above 3V. Then I had it set to 1.92A bulk charge. Fire extinguisher nearby lol
Can't recommend charging cells that have fallen below their official stop voltage- the liability and risk is too high. However, numerous papers have shown that the serious risks happen if they're reverse charged.
I wouldn't use anything but a bench supply stuck outside though.
As I said, it's against all recommendations. I've done this a few times over the years though and haven't hit the copper shunting problem described in literature. If they did have that problem my charger would pick up the short and stop charging them.
I did have a failure once and it was on a new molicel. I damaged the outside wrap of a cell while building a pack and it had a short and self-discharged the cell, likely reverse charging it in use. A week or so later the charger rejected it. When I pulled it out it was a fully shorted cell that would accept no charge, but it did not catch fire.
> How do you even drain a 3.7V lithium
> ion battery below 3.3V?
Connect the + and - terminals with an appropriately sized resistor, it'll drain all the way to 0V.
> My devices that use 18650s will
> not let them go below that.
Because you're not using the + and - terminals, you're using the + and - supply of a BMS, which is connected to those terminals. For this sort of testing you need to bypass the BMS, which'll have its own voltage cutoffs.
I understand you can discharge a battery completely with a resistor, just like any other capacitor. I also know there’s a battery controller in my device.
My actual question should’ve been ‘Do people really use lithium ion batteries in devices without battery managers?’ I absolutely would not.
Neywiny's comment upthread isn't that you should use these without a BMS, but that the review is relatively less useful because it's stopping testing at a relatively high voltage. E.g. if you search for "panasonic_ncr18650b.pdf" you'll find that Panasonic's own datasheets use a cutoff of 2.5v.
Some do. Anecdotally, some (uncommon, enthusiast-grade) flashlights I use don't have battery managers/over discharge protection, though most of mine do. If you can bear the responsibility of maintaining and storing the batteries properly, IMO there's no significant problems.
4.2v for 100% SoC (State of Charge, charging), settles down closer to 4v once charging stops (likely not exactly correct, just my rote memory). 80-90% of capacity/SoC is between 3.7-3.8v.
The remaining 10-20% is above 3.8 and below 3.70v. 4.2v is the max to ever intentionally apply to a cell, and 2.5v is the minimum anybody specs as end of discharge.
As such- the "nominal" voltage is 3.7v or 3.8v.
Possibilities for 3.3v cut off include: LEDs' combined forward Voltage, a BMS set to that voltage, high drain applications pulling the voltage below a lower (potentially much lower at 10C to 50C discharge) cutoff voltage.
These are, of course, for NMC lithium secondary/lithium ion cells. NOT LiFePO4/LFP/LTO/Na-ion.
Theres lots of FUD, but most lithium stories are Li-Po cells (cell phones, RAdio-Control, laptops). Of the Li-Po's- most of them are for RC usage without any inbuilt protection.
LiPo's are beat treated like they're ziplock baggies full of 100mL of gasoline. If you handle them, I suggest buying an Ash Pot- their double walls give you a chance of containing a flaming pack. Best to just do it outside though.
Vapcell is very popular in the flashlight community for providing unusual sizes like 16340, 18350, 18500, 26800, etc.
They re-wrap other manufacturer's cells (but don't disclose who). I dislike this practice because, along with not knowing who makes the cell, you lose the original mfg batch codes, etc.
Sometimes they will simply rewrap something like a Samsung 50S. Those will be fine. But others ... who knows.
Thats a policy to have when buying things in general. Even more so when gram for gram it holds 1% the energy of gasoline... but doesn't need the help of oxygen, or any decernable trigger to make a hash of things.
A common practice by shady sellers with 18650 lithium cells is to advertise a group of 4 of them as "2000mAh", but it's the total of each cell, not the individual cell ratings. So you're really getting four 500mAh batteries, which really sucks.
problem with Lumafield is their pricing. Last time I checked with them. They don't sell the CT machine. It was a lease/subscription at yearly cost of $75,000. It was not justified for what we are doing.
But a conventional CT scanner costs $300k-$1m plus $50-100k per year for software licenses and maintenance contract. Lumafield’s basically giving you the entire system for just the annual software/support cost on an older-style machine. My company is considering one and it’s a more attractive model once you start comparing realistic costs.
I wonder if ultrasound techniques might provide an alternative. If it takes 10+ hours to do a CT inspection, as someone pointed out elsewhere (if I understood correctly), then that's a lot of DSP time.
For that matter, jeez, how long does it take to just whip out a Dremel tool and take the battery apart for inspection? I must have misunderstood that comment.
After we monitored many battery fires, we decided to build a casing which can sustain lithium fires for typical e-bike batteries: https://www.youtube.com/watch?v=v0NXXfCA2CY
Your site (if this is your YouTube video) indicates Bosch compatibility with gen 2 motors[A]. I'm curious as to:
1. It says "Protocol implemented = no", but "Powers bike = yes", you can power a Bosch gen 2 motor without implementing the protocol, presumably this is referring to the CAN wire on the battery.
2. Your battery kit is 316 EUR without cells, and your BMS spare part is 99 EUR. If you can talk to Bosch motors then presumably this is where that special sauce is.
I for one might be interested in just something that serves to talk with the Bosch motor, and allows one to provide any arbitrary 36v source, do you or anyone else make/sell such a thing?
E.g. for range extending a cargo bike I'd find the cost/weight ratio of a beefy ~1220 Wh AGM 12v car battery coupled with a boost converter much more appealing than something that emulates the form factor of a ~500 Wh Bosch battery with Li-Ion 18650 cells, the range more than makes up for the extra weight.
Yes! We're compatible with Gen 1/2/3 (but not "smart system" yet!) the battery is indeed 316 eur + about 40/50 eur for the cells (while a comparable Bosch battery would be 700/800 eur)
Perhaps you can send us an email at contact@gouach.com with more details on your setup, so I can transfer it to the technical team?
Yes. This is where the cell's current warms up the cells, you can picture Ri as in series with the cell current so the power it develops there is Ri * I * I. As Ri goes up the power goes up, the ratio between the load resistance and the pack internal resistance determines how large a fraction of the total gets dumped into the battery as heat. That's why you want to be careful with ensuring the batteries can shed that heat faster than they develop it, otherwise you might end up with a thermal runaway even if the pack wasn't strictly speaking broken.
Most half decent cell testers report Ri, and any deviation from the norm is a good reason to discard a cell. I test the cells of all the packs I build and I've had to throw out two out of a few hundred cells over time so this isn't common but it does happen (those two were Sanyo's, I normally buy Samsung but those were out of stock so in my book Samsung > Sanyo but my sample size is still small enough that it could have been a random issue, and they're all reclaimed cells so that may have been due to some cause that was beyond the manufacturers control).
Thanks! For whatever reason the battery datasheets I've been looking at this week called it IR. I'll definitely be including it in the next cell tester I build.
That's an interesting thing you've got there. If this were standardized I might actually take the time to learn some of them. My own language has a whole pile of diacritical marks that I never use, I just transliterate everything to ASCII and call it a day. This obviously is very broken but what with every editor and every OS having their own way of doing super/subscript and various composition method it never seemed worth the trouble. But some people can get very offended when you don't write their name properly. German has picked some sensible transliteration defaults now that allow you to write German without resorting to special letters. But in other languages they would be horrified by such a thing. And for things like superscripts, subscripts and so on it is even worse.
I didn't realize Dutch had a lot of diacritics! I often use Emacs's builtin input methods in Emacs, for example when writing in Spanish, but Compose works in Emacs too. Because I don't yet have any Wayland devices, Android is the only operating environment where I can't use that .Xcompose file.
Would be interesting indeed! For now we don't build our own cells (the most important part for defects), in order to let our users choose their own depending on their needs (18650, 21700, brand, second-life, etc)
We're building a product, but that's easy to adapt to many setup (we have many end-users mounting our battery on their e-bikes, for now we are compatible with most systems, Bafang, Brose, Bosch, etc, working on Shimano now)
My understanding is that material composition can make a CT scan take a really long time. It makes sense to me that scanning a battery would be pretty slow, given what they're made out of.
sorry for a dumb question but are old dead cells still dangerous just sitting around?
I discovered an ancient powerbank the size of a deck of cards that I had not charged in many years, was blown up like a football (imagine an a sealed envelope but full of air)
So that's a dead cell which shouldn't have a charge left but I guess the chemistry is releasing gas?
Scared me, wrapped it in aluminum foil and put it outside asap
I get they won't disappear entirely, but what are the applications that 200-225 wh/kg LFP and forthcoming 175 wh/kg sodium ion can't handle with their much better safety profiles?
For higher density applications, semi-solid state is coming for nickel/cobalt chemistry lithium ion, and it has much better fire safety.
LFP is really catching up in terms of energy density, but not power density. LFP cells would give incredibly weak performance in something like a power tool battery, because they can't supply anywhere near the peak current of modern NMC cells, particularly pouch cells or tabless cylindrical cells.
For bulk storage LFP is a no-brainer, but there are still a lot of applications where you really want fast charging or need to handle big surges of current.
Note that batteries that catch on fire are a form of what AI safety researchers would call unaligned AI. Incentive structures that lead to the production of unaligned dumb AI appear to be quite an under researched blind spot in AI safety research.
I just got a new tenant in my rental house and this time I had to add a clause to the lease enumerating brands of lithium-ion batteries the tenant is allowed to keep on the premises. These things are basically grenades that you can buy for $2 on Temu. Stronger regulations needed.
I'm not a landowner, but (subject to the local laws of course) I imagine a safer course of action would be decent home insurance. Realistically, there's a thousand other ways things can go disastrously wrong, including nothing that could be the tenant's fault (like natural disasters).
I'd like to argue that electric Rechauds are superior anyway. Fuel paste or gas always seems to run out just before you're finished, everything cools down while refilling and then you have to get the fluid up to temperature again.
Safety around children or tipsy people is just the bonus on top.
I found out today that the rechargeable batteries in my cordless landline phone are basically fake. They're NiMH AAAs, Highpower brand. I bought replacements because they were dying, and the replacements (rewraps by a domestic importer) weigh twice as much, 13 grams instead of 7, and purport to have 1000mAh capacity instead of the 300 advertised by the Highpower cells. Hmm, maybe that's why the phone wasn't working very well...
But those are (probably!) NiMH. No idea what brand of lions are in this cellphone, my laptop, my other laptop, my MicroPC, my other cellphone, etc.
Doesn't the same question apply though? How is the bicycle and scooter owner supposed to find out the exact brand of the cells used, rip apart the pack just because the landlord doesn't have insurance/require tenant to get insurance?
Yes, especially wearables and toys. Those are a real problem. One of my kids was gifted a toy that had an embedded Lithium Ion pouch battery of spectacularly bad quality, the pouch had already inflated to the point that it was unsafe to dispose of when he got it. I ended up hand delivering the whole thing to the local disposal site where they have the proper gear to deal with these.
It does help. It raise the opportunity to discuss it, which is helpful because not everyone is aware that this is a problem, and like many other lease clauses it is there to assign blame in case an exceptionally bad event comes to pass.
Interesting, and ominous. If the place burns down and they find the remains of a "TrustFire" battery in the debris, they might try to refuse coverage, leaving you with the task of recovering damages from the tenant. And good luck with that...
Nah, tenants will sign just to move in, and forget about this clause. Just like any tenant that smokes weed disregards no drug clauses. Tenants are going to do what tenants do. Unless you're doing routine walk throughs looking at every single thing in the place that could use a battery, then you'll never know. It's a useless "regulation", and we have plenty of those in the world already.
And the "intelligent" part makes them realize that you get absolutely nowhere if you try to strictly follow all rules (there's a reason why "work to rule" is an effective sabotage strategy), and that the path of least resistance is to sign and ignore it.
It’s not unjustified. I’m a tenant. I don’t read all of the clauses. I’m a normal well meaning intelligent person. Does not change anything about what I said.
To save everyone the hassle of filling out the "get the report" form:
https://7802750.fs1.hubspotusercontent-na1.net/hubfs/7802750...
FWIW I found the report's summary (a few days ago when this was also discussed) essential for clarifying for me what the linked "article" was talking about regarding "anode overhang" and "edge alignment".
To summarize it myself, the battery is cylindrically wrapped sheets of anode/cathode material, and you want the top edge to have a straight line consistently having the anode layers (|) sticking out beyond the cathode layers ()
edit: Welp, the unicode I illustrated with got stripped out; so trying again with pipes
The pics with red and blue dots didn't immediately make this obvious to me, but made sense once I understood the "overhang" meaning.Is this what's shown in the photo here? https://imgz.org/i55rjGiq/
Yep! where the green arrow is pointing is what I was ascii-lustrating
So the big danger here is an internal short being far more likely?
I seem to recall this being a factor in the Samsung Galaxy Note 7 battery fire debacle. The article linked below has an xray image where you can see the anode/cathode overhanging and then being shorted by subsequent damage.
https://www.theguardian.com/technology/2017/jan/23/samsung-b...
That was my general sense. And that "nominal" is really easy to identify visually with a (relatively slow) scan. I'd guess that means it's a clear quality control thing you (i.e. battery pack makers who are buying the cells) can expect the better manufacturers to do, and pay a slight premium for.
thank you
I'm not sure who is in charge of advertising at lumafield but in the last few weeks I've seen James Hoffman use lumafield CR scans on coffee pucks, Jeff Geerling use them on a Pi 500+, and now this. I'm probably not their target market but I definitely know who they are now.
It's pretty smart, IMO. They are targeting the nerds watching tech videos in their offtime. That's a great way to plant their name into the heads of said nerds when the boss decides they need a CT scanner for whatever reason.
Advertising works. Shocking, isn't it?
Seems like a good time to highlight this video from Grin Technologies and their experience with ebikes over the years.
https://www.youtube.com/watch?v=j92Gt4VviSQ
Summary Statement: He summarizes the results of the "sabotaging" attempts by saying, "we just couldn't for the life of ourselves get a nonprotected modern lithium battery to do anything" [02:40:27], in terms of causing a fire. (referring to 18650s)
There are certainly problems out there with cells but it was a surprising statement from someone with a ton of real-world experience. Also they are a very conscientious company so they don't deal with dodgy stuff if they can avoid it.
It's a long video but one takeaway is to only use cells from the top manufacturers: Samsung, Panasonic, LG and Sony. They are amazingly safe.
Unfortunately, for products with batteries in non-standard form factors, we rarely have a choice of a manufacturer. For example, with home robot vacuums, we can only hope that brands will use top quality cells, but the information what cells are used is not even available to the customer. My Neato vacuum still runs great, but now that the company is out of business, my only battery replacement options are from no-name brands, with zero visibility of what cells are used internally.
> For example, with home robot vacuums, we can only hope that brands will use top quality cells, but the information what cells are used is not even available to the customer.
Hardware used to come with diagrams & schematics, for self-service and repair. This was a courtesy, but I guess manufacturers figured out it's better to make the consumer buy a new model. (AKA part of the reason why Commodore went bankrupt.)
Meanwhile we've been talking and implementing measures such as lists of ingredients and nutrients in food, SBOMs in software, privacy/tracking transparency, etc. Let's push it a little further.
You also have the option of building your own battery pack for these, or to disassemble an existing pack and replacing the cells. How difficult that is depends on the manufacturer, but from a quick look at the Neato packs I see it looks relatively trivial.
I'm in the process of replacing the battery in my old robot vacuum right now, and for the amount of time spent doing that, I could buy a whole new vacuum. It's a pity, because the battery itself can be replaced just by plugging it in, but all the batteries I could find were AliExpress fakes, so my two options are either "more e-waste" or "spend $500 in time doing it myself".
Some of us enjoy fixing things like these over and above the hypothetically fungible billable hour, and whether you can substitute some time in an evening with a billable hour or three is highly dependent on your employment situation.
But in this case the relevant cost under discussion isn't that of a replacement vacuum cleaner, but what value you assign to your house not burning down due to a crappy 18650 cell, or the anxiety of worrying that that'll happen.
Well, I don't enjoy making the hundredth battery pack, so I'm counting it against the hypothetically fungible billable hour.
The cost should be the cost of a good-quality battery pack from the factory, which I can only get right now as part of the vacuum, unfortunately.
Unfortunately the cheap "fatbikes" every kid has here these days have no premium cells and even worse chargers and usually poor or no balancing in the BMS. I don't expect them to not catch fire and my HOA is considering to ban charging ebikes in the basement (where you put your bike) due to that. End result is likely that people with more expensive bikes and cells adhere to this and charge in the house while the cheap ass bikes will still be charged in the basement and the fire department can flood it once again when it all goes up in flames.
Molicell?
I have one in 21700 and it seems a great battery so far. Otherwise I'm a Panasonic guy.
I ask because it sits on my forehead, inside a headlamp. Having my hands tied, addressing a problem quickly might be difficult. And them rascals get toasty fast when they ignite.
Molicel is top tier - their P50B is the best 21700 cell available on the open market. Eve, BAK and Ampace also make some really good stuff, although they can't match the performance of Molicel.
I came to the same conclusion when upgrading from 18650s to 21700s, I spent a long time trying to weed out the poorly binned rewards, and the minefield of lithium batteries. They weren't cheap but have been happy with their performance.
There are a lot of people out there that see 18650 or 21700 and think a lithium ion battery is a lithium ion battery and they're all the same (i.e. trying to pull 20 amps from a 2 amp peak battery). I miss one of the father's of liion battery education, Mooch (from ecigarettes forum) who had a whole methodology of testing, and educating people.
I ask because it sits on my forehead, inside a headlamp. Having my hands tied, addressing a problem quickly might be difficult
Gotta ask what kind of sport, profession, or B&D game involves wearing a headlamp while your hands are tied.
Yeah, Molicel are quality cells as well.
The anecdata is Molicell is good stuff. Was going to include that but I have no references.
lygte-info.dk rates them quite highly iirc.
I imagine the counterfeit market for lithium batteries is quite large, so maybe not always amazingly safe.
I've seen other videos of people driving nails into 18650s and "spicy pillow" square cells, and most of them didn't even let off a puff of smoke. What the vaping community was doing 10-15 years ago to launch batteries into the ceiling is beyond me.
The vaping community was basically shorting the cells. I'm not sure how a modern 18650 or prismatic cell would handle that.
Your best predictor of cell failure is brand + where you sourced it. Good brand cells sourced through a reliable channel are pretty much impossible to get a failure out of without gross abuse of the cells.
But far more dangerous than single cell failure is pack failure and there the quality of the welding and the balance wires is probably a much bigger factor than bad quality cells. You can easily create a nice looking bomb from grade A cells, and even manufacturers with good name recognition will mess this up from time to time.
So buy packs made with quality cells and ensure that whoever makes the pack has proper welding gear and QA in place to avoid surprises. Never ever use cells without a BMS unless they are in a 1S configuration.
> So buy packs made with quality cells and ensure that whoever makes the pack has proper welding gear and QA in place to avoid surprises. Never ever use cells without a BMS unless they are in a 1S configuration.
How do you put that advice into action? When I'm in an electronics store, they don't typically let you look at the welds inside each battery bank. (And if they did, I have no idea what I'd be looking out for.)
Good point. It requires disassembly, and if you're not comfortable with that it is a lot harder to get a good idea on this. But there are plenty of videos and photos online of various disassembled packs from high volume manufacturers.
Quality cells are a relatively small group of brands so that should be easy enough to check for, and you'll know looking at just one side of a cell group whether or not it was put together half decently or whether it is messy.
Stuff to look for: loose balance wires, bad welds (welds that don't penetrate so they're loose), pointy edges of connecting strips that touch the plastic insulation of the cells, insufficient spacing between the cells, insufficient insulation near the welds.
For one-off purchases this won't help, but if you are a reseller or larger purchaser then it definitely is a good idea to tear down a pack and inspect.
Your could take your CT scanner to the store to look at the cells.
Cells are subject to aggressive binning – akin to the early days of MOS process. And specs and process capability adhesion in the industry are not as "serious" as they are in the modern, U.S.-led semiconductor industry.
Source: I work on 100% Si anode batteries constructed in part with a litho-derived laser process at Enovix.
Last time I checked, most manufacturing of semiconductors isn't done in the US... sure, they are leading in design, but the manufacturing is elsewhere.
Just a few days ago the apartment above ours burned down alledegly because of an explosion of an ebike battery. They left it charging overnight and exploded in the morning. Fortunately nobody got hurt, but it was really scary experience.
This is actually pretty common with e-bike batteries (as in fires per thousand when compared to other battery packs). Dunno why.
Extremely large currents and a race to the bottom price (despite lithium-ion being expensive, people are eager to get “value” for the money which rewards conpanies which cut corners).
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I find their table of advertised vs actual capacity to be misleadingly negative. They only discharged to 3v. 2.7 could be viewed as more standard. 2.5 is not unheard of. For example, the vapvell 4000 they said was around 3000. They even have a note that says that isn't a reasonable capacity estimate. And yet they still put the percentage and the number. As if they've falsely advertised. However, if you go to vapcell's graphs on their website, it all tracks. Feels out of scope for the report and shouldn't have been done
I went to vapcell's website, looked at their charts and specifications. I disagree with your assessment.
They specify 3800mAh minimum discharge at 0.2C for their 4000mAh cell. They don't show a discharge curve at 0.2C in their charts (would be 0.8A) but they do have a 1A discharge. When the 1A discharge curve reaches 3V, the energy discharged is right around 3800mAh.
Lumafield discharged at 0.2C, and they saw only 3055mAh.
Vapcell's site mostly shows high current discharge curves, where yes there is more capacity below 3V available, but with Li-ion at lower currents, the curve is very steep past 3V, not much more capacity left after that. And when you're discharging at high current you won't expect to get the full capacity, anyway.
I'll also take this time to point out lygte-info which is a treasure trove of battery tests.
[0] https://www.vapcelltech.com/h-pd-193.html
[1] https://www.lygte-info.dk/
It even says "Conservative discharge that would not extract maximum performance". A lot of electronics built for li-ion will not work <3V so it's a perfectly reasonable benchmark, especially to show the difference between brands.
A lot of electronics need a 3.3v rail and produce that from a linear or buck regulator, so won't work below 3.4 volts.
Battery operated devices, while nominally 3.3V, commonly work down to 3V or even 2.7V in line with the voltage curve of lithium (not li-ion) coin batteries.
How do you even drain a 3.7V lithium ion battery below 3.3V? My devices that use 18650s will not let them go below that. Is it 3.3V nominal and the actual voltage is lower, like how they’re 4.2V fully charged?
I guess leave them sitting in a laptop in a barn for a few years. I was given some old shit gateway the other day, tried to charge it, no dice. Ripped the pack apart to find samsung 18650's with approx 0.7V voltage.
Against ALL recommendations I put these cells into a MC3000 and they charged up just fine to 4.2V. It does a 0.15A charge per cell until it gets above 3V. Then I had it set to 1.92A bulk charge. Fire extinguisher nearby lol
Can't recommend charging cells that have fallen below their official stop voltage- the liability and risk is too high. However, numerous papers have shown that the serious risks happen if they're reverse charged.
I wouldn't use anything but a bench supply stuck outside though.
As I said, it's against all recommendations. I've done this a few times over the years though and haven't hit the copper shunting problem described in literature. If they did have that problem my charger would pick up the short and stop charging them.
I did have a failure once and it was on a new molicel. I damaged the outside wrap of a cell while building a pack and it had a short and self-discharged the cell, likely reverse charging it in use. A week or so later the charger rejected it. When I pulled it out it was a fully shorted cell that would accept no charge, but it did not catch fire.
I understand you can discharge a battery completely with a resistor, just like any other capacitor. I also know there’s a battery controller in my device.
My actual question should’ve been ‘Do people really use lithium ion batteries in devices without battery managers?’ I absolutely would not.
Neywiny's comment upthread isn't that you should use these without a BMS, but that the review is relatively less useful because it's stopping testing at a relatively high voltage. E.g. if you search for "panasonic_ncr18650b.pdf" you'll find that Panasonic's own datasheets use a cutoff of 2.5v.
Some do. Anecdotally, some (uncommon, enthusiast-grade) flashlights I use don't have battery managers/over discharge protection, though most of mine do. If you can bear the responsibility of maintaining and storing the batteries properly, IMO there's no significant problems.
4.2v for 100% SoC (State of Charge, charging), settles down closer to 4v once charging stops (likely not exactly correct, just my rote memory). 80-90% of capacity/SoC is between 3.7-3.8v.
The remaining 10-20% is above 3.8 and below 3.70v. 4.2v is the max to ever intentionally apply to a cell, and 2.5v is the minimum anybody specs as end of discharge.
As such- the "nominal" voltage is 3.7v or 3.8v.
Possibilities for 3.3v cut off include: LEDs' combined forward Voltage, a BMS set to that voltage, high drain applications pulling the voltage below a lower (potentially much lower at 10C to 50C discharge) cutoff voltage.
These are, of course, for NMC lithium secondary/lithium ion cells. NOT LiFePO4/LFP/LTO/Na-ion.
Theres lots of FUD, but most lithium stories are Li-Po cells (cell phones, RAdio-Control, laptops). Of the Li-Po's- most of them are for RC usage without any inbuilt protection.
LiPo's are beat treated like they're ziplock baggies full of 100mL of gasoline. If you handle them, I suggest buying an Ash Pot- their double walls give you a chance of containing a flaming pack. Best to just do it outside though.
> Efest, Vapcell, Trustfire, Treasurecase, Benkia, SOOCOOL, Maxiaeon
Sounds like a bunch of amazon merchants. Imagine buying lithium ion batteries from a vendor with "trust" and "fire" in their name at the same time.
Vapcell is very popular in the flashlight community for providing unusual sizes like 16340, 18350, 18500, 26800, etc.
They re-wrap other manufacturer's cells (but don't disclose who). I dislike this practice because, along with not knowing who makes the cell, you lose the original mfg batch codes, etc.
Sometimes they will simply rewrap something like a Samsung 50S. Those will be fine. But others ... who knows.
The conclusion I drew from this is that if real capacity is much less than advertised the battery is best avoided.
Thats a policy to have when buying things in general. Even more so when gram for gram it holds 1% the energy of gasoline... but doesn't need the help of oxygen, or any decernable trigger to make a hash of things.
A common practice by shady sellers with 18650 lithium cells is to advertise a group of 4 of them as "2000mAh", but it's the total of each cell, not the individual cell ratings. So you're really getting four 500mAh batteries, which really sucks.
problem with Lumafield is their pricing. Last time I checked with them. They don't sell the CT machine. It was a lease/subscription at yearly cost of $75,000. It was not justified for what we are doing.
But a conventional CT scanner costs $300k-$1m plus $50-100k per year for software licenses and maintenance contract. Lumafield’s basically giving you the entire system for just the annual software/support cost on an older-style machine. My company is considering one and it’s a more attractive model once you start comparing realistic costs.
I wonder if ultrasound techniques might provide an alternative. If it takes 10+ hours to do a CT inspection, as someone pointed out elsewhere (if I understood correctly), then that's a lot of DSP time.
For that matter, jeez, how long does it take to just whip out a Dremel tool and take the battery apart for inspection? I must have misunderstood that comment.
After we monitored many battery fires, we decided to build a casing which can sustain lithium fires for typical e-bike batteries: https://www.youtube.com/watch?v=v0NXXfCA2CY
I think you mean "contain". Very nice.
Indeed! Thanks :)
Your site (if this is your YouTube video) indicates Bosch compatibility with gen 2 motors[A]. I'm curious as to:
1. It says "Protocol implemented = no", but "Powers bike = yes", you can power a Bosch gen 2 motor without implementing the protocol, presumably this is referring to the CAN wire on the battery.
2. Your battery kit is 316 EUR without cells, and your BMS spare part is 99 EUR. If you can talk to Bosch motors then presumably this is where that special sauce is.
I for one might be interested in just something that serves to talk with the Bosch motor, and allows one to provide any arbitrary 36v source, do you or anyone else make/sell such a thing?
E.g. for range extending a cargo bike I'd find the cost/weight ratio of a beefy ~1220 Wh AGM 12v car battery coupled with a boost converter much more appealing than something that emulates the form factor of a ~500 Wh Bosch battery with Li-Ion 18650 cells, the range more than makes up for the extra weight.
A. https://infinite-battery.com/pages/compatibility-guide-of-th...
Yes! We're compatible with Gen 1/2/3 (but not "smart system" yet!) the battery is indeed 316 eur + about 40/50 eur for the cells (while a comparable Bosch battery would be 700/800 eur)
Perhaps you can send us an email at contact@gouach.com with more details on your setup, so I can transfer it to the technical team?
Maybe complement that with a CT-scan of your batteries and AI to detect defects.
FLIR monitoring + Ri measurement is a much better predictor than a CT scan, especially because you're not going to do that continuously.
Ri is internal resistance?
Yes. This is where the cell's current warms up the cells, you can picture Ri as in series with the cell current so the power it develops there is Ri * I * I. As Ri goes up the power goes up, the ratio between the load resistance and the pack internal resistance determines how large a fraction of the total gets dumped into the battery as heat. That's why you want to be careful with ensuring the batteries can shed that heat faster than they develop it, otherwise you might end up with a thermal runaway even if the pack wasn't strictly speaking broken.
Most half decent cell testers report Ri, and any deviation from the norm is a good reason to discard a cell. I test the cells of all the packs I build and I've had to throw out two out of a few hundred cells over time so this isn't common but it does happen (those two were Sanyo's, I normally buy Samsung but those were out of stock so in my book Samsung > Sanyo but my sample size is still small enough that it could have been a random issue, and they're all reclaimed cells so that may have been due to some cause that was beyond the manufacturers control).
Thanks! For whatever reason the battery datasheets I've been looking at this week called it IR. I'll definitely be including it in the next cell tester I build.
IR = Infrared?
R = symbol of resistance
i = internal
https://en.wikipedia.org/wiki/Internal_resistance
So Rint is also used. The proper way would be with a subscript but I don't know how to do that.
There's a Compose key binding for it in https://github.com/kragen/xcompose/blob/master/dotXCompose. Usually a lowercase i is the small-signal current, but some ambiguity is probably unavoidable with short abbreviations.
That's an interesting thing you've got there. If this were standardized I might actually take the time to learn some of them. My own language has a whole pile of diacritical marks that I never use, I just transliterate everything to ASCII and call it a day. This obviously is very broken but what with every editor and every OS having their own way of doing super/subscript and various composition method it never seemed worth the trouble. But some people can get very offended when you don't write their name properly. German has picked some sensible transliteration defaults now that allow you to write German without resorting to special letters. But in other languages they would be horrified by such a thing. And for things like superscripts, subscripts and so on it is even worse.
I didn't realize Dutch had a lot of diacritics! I often use Emacs's builtin input methods in Emacs, for example when writing in Spanish, but Compose works in Emacs too. Because I don't yet have any Wayland devices, Android is the only operating environment where I can't use that .Xcompose file.
Would be interesting indeed! For now we don't build our own cells (the most important part for defects), in order to let our users choose their own depending on their needs (18650, 21700, brand, second-life, etc)
That's a great idea. Are you making a product or sharing the build?
https://infinite-battery.com/
(no affiliation)
We're building a product, but that's easy to adapt to many setup (we have many end-users mounting our battery on their e-bikes, for now we are compatible with most systems, Bafang, Brose, Bosch, etc, working on Shimano now)
Neat. How do bikes that have the battery entirely inside the metal downtube compare?
Edited: Now that I looked at your product I have low expectations for an unbiased answer :-|
We're working on an internal downtube battery too! It's basically the same tech, the batteries work the same, it's just the form-factor which changes
seems obvious in hindsight, but never knew CT scans are used in manufacturing QC
What about expensive cells? Any quality risks in them or they are perfect?
"Buyer beware" always applies, no exceptions.
I went down their rabbit hole, and a conventional tech CT is 10 hours??
That is possible, especially for very high resolution scans and dense materials.
I work with (other) desktop microCT scanners and the longest scan we did took longer than 40 hours.
My understanding is that material composition can make a CT scan take a really long time. It makes sense to me that scanning a battery would be pretty slow, given what they're made out of.
I just assumed it would be impractical due to physical changes of the object from multi-hour exposure to X-ray energy.
Metal objects don’t change that much due to the radiation.
I don't think ionizing atoms inside a battery will harm it. They don't have DNA.
I don't know about batteries, but ionizing radiation can definitely permanently damage microelectronics, and those don't have DNA either.
Thankfully functionality isn't usually necessary to get a successful scan, unlike living targets.
It can, yes, but batteries also don't have microelectronics.
sorry for a dumb question but are old dead cells still dangerous just sitting around?
I discovered an ancient powerbank the size of a deck of cards that I had not charged in many years, was blown up like a football (imagine an a sealed envelope but full of air)
So that's a dead cell which shouldn't have a charge left but I guess the chemistry is releasing gas?
Scared me, wrapped it in aluminum foil and put it outside asap
I get they won't disappear entirely, but what are the applications that 200-225 wh/kg LFP and forthcoming 175 wh/kg sodium ion can't handle with their much better safety profiles?
For higher density applications, semi-solid state is coming for nickel/cobalt chemistry lithium ion, and it has much better fire safety.
LFP is really catching up in terms of energy density, but not power density. LFP cells would give incredibly weak performance in something like a power tool battery, because they can't supply anywhere near the peak current of modern NMC cells, particularly pouch cells or tabless cylindrical cells.
For bulk storage LFP is a no-brainer, but there are still a lot of applications where you really want fast charging or need to handle big surges of current.
So semi-solid state then? What about sodium ion?
Drones seem like the biggest one? Maybe some drones can cope with the extra weight.
Note that batteries that catch on fire are a form of what AI safety researchers would call unaligned AI. Incentive structures that lead to the production of unaligned dumb AI appear to be quite an under researched blind spot in AI safety research.
I just got a new tenant in my rental house and this time I had to add a clause to the lease enumerating brands of lithium-ion batteries the tenant is allowed to keep on the premises. These things are basically grenades that you can buy for $2 on Temu. Stronger regulations needed.
I'm not a landowner, but (subject to the local laws of course) I imagine a safer course of action would be decent home insurance. Realistically, there's a thousand other ways things can go disastrously wrong, including nothing that could be the tenant's fault (like natural disasters).
Batteries? Picture a fondue going wrong.
If you've ever dealt with home insurance you try very hard to not have to deal with home insurance.
To say your goals are cross-aligned with theirs would be an understatement.
I'd like to argue that electric Rechauds are superior anyway. Fuel paste or gas always seems to run out just before you're finished, everything cools down while refilling and then you have to get the fluid up to temperature again. Safety around children or tipsy people is just the bonus on top.
I found out today that the rechargeable batteries in my cordless landline phone are basically fake. They're NiMH AAAs, Highpower brand. I bought replacements because they were dying, and the replacements (rewraps by a domestic importer) weigh twice as much, 13 grams instead of 7, and purport to have 1000mAh capacity instead of the 300 advertised by the Highpower cells. Hmm, maybe that's why the phone wasn't working very well...
But those are (probably!) NiMH. No idea what brand of lions are in this cellphone, my laptop, my other laptop, my MicroPC, my other cellphone, etc.
How is any tenant possibly supposed to comply with that? Rip every piece of electronics they buy apart to check?
It's about highly energetic battery packs for things like bicycles and scooters.
Doesn't the same question apply though? How is the bicycle and scooter owner supposed to find out the exact brand of the cells used, rip apart the pack just because the landlord doesn't have insurance/require tenant to get insurance?
Won't help much. Way too much cheap lithium ion crap with incapsulated batteries is flooding the markets
Yes, especially wearables and toys. Those are a real problem. One of my kids was gifted a toy that had an embedded Lithium Ion pouch battery of spectacularly bad quality, the pouch had already inflated to the point that it was unsafe to dispose of when he got it. I ended up hand delivering the whole thing to the local disposal site where they have the proper gear to deal with these.
It does help. It raise the opportunity to discuss it, which is helpful because not everyone is aware that this is a problem, and like many other lease clauses it is there to assign blame in case an exceptionally bad event comes to pass.
It's got to be tricky for people to know what cells they have inside their {phone, toothbrush, bike etc}.
like many other lease clauses it is there to assign blame in case an exceptionally bad event comes to pass
That sounds like a job for the insurance company. You do have insurance, right? Did they have any input on this clause?
They dictated it.
Interesting, and ominous. If the place burns down and they find the remains of a "TrustFire" battery in the debris, they might try to refuse coverage, leaving you with the task of recovering damages from the tenant. And good luck with that...
Nah, tenants will sign just to move in, and forget about this clause. Just like any tenant that smokes weed disregards no drug clauses. Tenants are going to do what tenants do. Unless you're doing routine walk throughs looking at every single thing in the place that could use a battery, then you'll never know. It's a useless "regulation", and we have plenty of those in the world already.
It's wrong to have an unjustified low opinions of tenants as a class. They are normal, well-meaning, intelligent people like any other.
A large majority of humans don't read EULAs.
A lease clause is useless for liability, because your landlord's insurance won't be able to shake down the tenant anyway.
Someday soon enough, your insurance might require a clause like that. It will still be ignored by tenants though.
And the "intelligent" part makes them realize that you get absolutely nowhere if you try to strictly follow all rules (there's a reason why "work to rule" is an effective sabotage strategy), and that the path of least resistance is to sign and ignore it.
It’s not unjustified. I’m a tenant. I don’t read all of the clauses. I’m a normal well meaning intelligent person. Does not change anything about what I said.