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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

#91

Post by VectorLock »

nubinetwork wrote: post #74
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…

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.

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

#92

Post by askl »

josephg wrote: post #27
jacquesm wrote: post #25

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 looki…

> 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.…

Your could take your CT scanner to the store to look at the cells.

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

#93

Post by avar »

stavros wrote: post #73
avar wrote: post #64

Earlier quoted context omitted.

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.

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

#94

Post by VectorLock »

adwn wrote: post #63
kragen wrote: post #56

Earlier quoted context omitted.

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.

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

#95

Post by dpedu »

MBCook wrote: post #40
gertlex wrote: post #38

Earlier quoted context omitted.

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 catho…

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...

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

#96

Post by VectorLock »

rollcat wrote: post #68
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.

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.

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

#97

Post by avar »

quickthrowman wrote: post #82
avar wrote: post #65

Earlier quoted context omitted.

> 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 h…

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.

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

#98

Post by nic547 »

rollcat wrote: post #68
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.

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.

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

#99

Post by stavros »

avar wrote: post #93
stavros wrote: post #73

Earlier quoted context omitted.

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 t…

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.

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

#100

Post by Liftyee »

malchow wrote: post #31

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.
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