To save everyone the hassle of filling out the "get the report" form:
https://7802750.fs1.hubspotusercontent-na1.net/hubfs/7802750...
replies(2):
https://7802750.fs1.hubspotusercontent-na1.net/hubfs/7802750...
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.
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...
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.
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.)
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
s/tenants/humans/g
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.
Source: I work on 100% Si anode batteries constructed in part with a litho-derived laser process at Enovix.
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.
That sounds like a job for the insurance company. You do have insurance, right? Did they have any input on this clause?
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.
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.
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 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.
I wouldn't use anything but a bench supply stuck outside though.
(no affiliation)
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.
For higher density applications, semi-solid state is coming for nickel/cobalt chemistry lithium ion, and it has much better fire safety.
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.
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).
> 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.
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.
Batteries? Picture a fondue going wrong.
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.
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
My actual question should’ve been ‘Do people really use lithium ion batteries in devices without battery managers?’ I absolutely would not.
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?
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.
https://www.theguardian.com/technology/2017/jan/23/samsung-b...
To say your goals are cross-aligned with theirs would be an understatement.
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.
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 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 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.
Gotta ask what kind of sport, profession, or B&D game involves wearing a headlamp while your hands are tied.
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.
Battery scans are very fast; the scans in the report took less than a second. Total cycle time on a Triton CT scanner is under 5 seconds when you account for part handling.
However, a LiPo cell that has entered Spicy Pillow mode (empty or not) can still theoretically burst, leaking or spraying toxic materials everywhere. So you were right to put it outside. Make sure you recycle it appropriately, so that it doesn't go into a landfill and poison the drinking water of our grandchildren someday.
Based on those stats, it sure sounds like the following is happening:
1. The reputable OEMs (Samsung, Panasonic, Murata in this study) do adequate quality control for defective batteries. The low-cost OEMs do not do adequate quality control. 2. Some portion of the defective or not-fully-tested batteries from the reputable OEMs get "diverted" to rewrappers, who essentially just relabel the batteries without doing any further testing.
Is that a correct read?