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CT scans of 1k lithium-ion batteries show quality risks in inexpensive cells

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Re: CT scans of 1k lithium-ion batteries show quality risks in inexpensive cells

#61

Post by jacquesm »

kragen wrote: post #55
jacquesm wrote: post #23

Earlier quoted context omitted.

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).

Re: CT scans of 1k lithium-ion batteries show quality risks in inexpensive cells

#62

Post by consp »

bahmboo wrote: post #50
bahmboo wrote: post #36

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 ar…

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 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.

Re: CT scans of 1k lithium-ion batteries show quality risks in inexpensive cells

#63

Post by adwn »

kragen wrote: post #56
xattt wrote: post #39

Earlier quoted context omitted.

I just assumed it would be impractical due to physical changes of the object from multi-hour exposure to X-ray energy.

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.

Re: CT scans of 1k lithium-ion batteries show quality risks in inexpensive cells

#64

Post by avar »

mixedbit wrote: post #60
bahmboo wrote: post #50

Earlier quoted context omitted.

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-nam…

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.

Re: CT scans of 1k lithium-ion batteries show quality risks in inexpensive cells

#65

Post by avar »

quickthrowman wrote: post #19
Neywiny wrote: post #4

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'…

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?

    > 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.

Re: CT scans of 1k lithium-ion batteries show quality risks in inexpensive cells

#67

Post by rollcat »

mixedbit wrote: post #60
bahmboo wrote: post #50

Earlier quoted context omitted.

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-nam…

> 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.

Re: CT scans of 1k lithium-ion batteries show quality risks in inexpensive cells

#68

Post by rollcat »

jeffbee wrote: post #12

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.

Re: CT scans of 1k lithium-ion batteries show quality risks in inexpensive cells

#69

Post by fnordian_slip »

eth0up wrote: post #51
bahmboo wrote: post #50

Earlier quoted context omitted.

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.

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.

lygte-info.dk rates them quite highly iirc.

Re: CT scans of 1k lithium-ion batteries show quality risks in inexpensive cells

#70

Post by jdietrich »

eth0up wrote: post #51
bahmboo wrote: post #50

Earlier quoted context omitted.

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.

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.
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