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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

#101

Post by Liftyee »

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.

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.

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

#102

Post by kragen »

jacquesm wrote: post #61
kragen wrote: post #55

Earlier quoted context omitted.

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…

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.

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

#103

Post by kragen »

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.

It can, yes, but batteries also don't have microelectronics.

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

#104

Post by AtlasBarfed »

jdietrich wrote: post #71
AtlasBarfed wrote: post #53

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 ne…

So semi-solid state then? What about sodium ion?

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

#105

Post by dylan604 »

jeffbee wrote: post #21
dylan604 wrote: post #17

Earlier quoted context omitted.

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.

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.

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

#106

Post by jacquesm »

kragen wrote: post #102
jacquesm wrote: post #61

Earlier quoted context omitted.

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…

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.

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

#107

Post by Adachi91 »

jdietrich wrote: post #70
eth0up wrote: post #51

Earlier quoted context omitted.

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.

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

#108

Post by oulipo2 »

jeffbee wrote: post #14
oulipo2 wrote: post #8

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

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

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

#109

Post by gertlex »

stavros wrote: post #72
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…

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

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

#110

Post by habi »

xattt wrote: post #32

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.

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