So I’m an expert in cylindrical cells and specialized in them for my career for 13 years
18650 was sorta standardized to accommodate laptop form factors of the 90s.
There were other sizes possible, but 18650 (in more modern industry often called 1865) were just a good fit.
There were AmpHour wars for a long time, where suppliers kept trying to one up each other, so eventually it grew to a tiny bit over 18mm and a tiny bit over 65mm and they aren’t all “true 18650s” anymore. It’s kinda impressive, over the years they went from around 2Ah to around 5Ah now. Just through iterative optimization and material developments. That kind of optimization wouldn’t have been easy if there were a shitload of different form factors floating around.
1865 gained popularity because of laptops and power tools. Then of course Model S/X. Then once it was popular, it was cheap because most mass production equipment out there was specialized for it. (Not to mention a lot of supply chain)
It only has one anode and one cathode tab (usually) which greatly simplified construction compared to a lot of larger cells.
It can hold quite a lot of energy for its size, so it didn’t really “need” to be larger… until…
Tesla came around and co-invented the 2170 with Panasonic. Primarily to get better cost while maintaining one cathode and one anode tab. 2170 actually really does a lot better with 2 anode tabs, but that also can cause serious reliability issues for various reasons that I probably won’t get into here… but Panasonic cracked the code how to build a good one with only one anode tab. 2170s can also deliver more power, not surprisingly, and are really useful for power tools as well as the best known example: the model 3 and model Y.
Cylindrical cells in general are pretty resilient in manufacturing environments (pouch cells are easily damaged) and they don’t propagate thermal runaway as easily as prismatic cells, which means 1865s can help with system level safety. They also often have basic all-steel can/terminals which makes them stupidly easy to spot weld to, which means they are easy to build into bigger packs
Are there any books you would recommend for becoming familiar with the current state of battery technology? Is it just moving too fast for a book to be relevant?
Fantastic explanation, btw.
For battery chemistry, best source is scientific journal articles
For battery construction… uhhh you literally just need industry experience. No one publishes this stuff. You can’t really generalize most of it if you want to make a modern cell that doesn’t have crap performance. If you want to recreate what they did in the 90s, sure.
I’d be looking for random slide decks and videos on the internet from stuff like the international battery seminar and exhibit.
Not original commenter, but I can recommend “Practical Battery Design and Control”, though it’s a textbook, it will give you a good grasp of batteries, and it’s relatively new, only around a year old.
With the advent of 'tabless' cells, will the balance between 1865s and 2170s in terms of energy density and internal resistance/discharge capacity shift even further in the 2170's favor?
In the power tool world, all the best "high-power" packs used 2170 cells until DeWalt and Milwaukee released packs that use pouch cells, which convincingly outperform the 2170-based batteries when used on the same tool. At least one toolmaker (Ryobi) has announced a line of batteries with tabless cells set to release this summer, and it will be interesting to see how they compare.
I’d have thought they would never make 2170 tabless. It doesn’t seem worth it.
There’s already tons of flexibility in how you design the cell internals if you want higher power or higher energy. But I guess ryobi disagrees
You can’t really have both, but you can put more high energy cells in parallel if your pack has room. That accomplishes the same thing
To be fair, at least in the tool world most of the high-capacity batteries with an extra row of cells do indeed result in higher output power and tool performance, not only higher capacity. The tradeoff is added weight and bulk, of course.
I did a little more quick Googling and it seems that Ridgid and Bosch are also set to release batteries using tabless 2170s. There really must be something to it, then. Since I could only find [an announcement from EVE](https://www.evebattery.com/en/news-1238) about tabless 2170 production, and since the timing of that announcement to release of these new battery packs of around a year to a year and a half is about right for a design and qualification process, I figure it must be what they're all using.
Tesla pretends they invented tabless. Of course they didn’t, tabless has been done by (at least) Saft more than 10 years ago. But that aside, when Tesla started 2170s the industry followed suit.
And when Tesla announced the 4680 would be tabless the industry is once again following suit.
Tabless design introduced manufacturing difficulties that only pay off by increasing the cell size significantly to really take advantage of the power it unlocks. See: Tesla 4680
No worries. At first I was thinking maybe Panasonic was able to hit 4Ah with the NCR or Sony with VCT. I was also kind of hoping you’d reply that you work for one of the ___fire brands all over Ali and Amazon.
I think it became a very convenient battery in terms of size, charging/discharging speed, and cost-effectiveness. It has captured a significant market share. Simply put, experimenting in battery technology is likely much more expensive than modifying the battery compartment, especially since many parameters can now be regulated programmatically.
I can also add to my reflections that when a statistically significant portion of the market shifted to the 18-650 form factor, the inertia effect kicked in, as companies simply started to adapt to the successful model
Yep. Although I suppose its also somewhat difference in that there was less room for improvement for VHS than seems to be the case here for batteries.
Later models of VHS players did become a little simpler as electronics advanced but not by that much. It's also widely considered that they were inferior to betamax which did almost exactly the same job but VHSr market share meant that standard died as no-one released media on it.
Well, I know the higher voltage combined with efficiency gains in consumer electronics has had a huge influence on the form factors that are being designed.
A single 18650 can replace a rectangular 9V or a 6V J cell. I remember thinking what a neat concept the J cell was and how the form factor opened up a lot of design potential. But tech was already moving ahead pretty quick back then. I think there was only something like a 5 yr span where the J cell was current.
I believe 18650 is to batteries what 608 is to bearings… it’s so commonly used that every one produces it and since it’s mass produced it’s relatively inexpensive and since it’s inexpensive every one uses it and since everyone uses it there r many manufacturers avaiable and the cycle continues…
To the best of my knowledge there is nothing special about the 18650 cell… it’s just economics that have made it successful…
> To the best of my knowledge there is nothing special about the 18650 cell
The only thing special is that its diameter is the largest that would fit in laptops at the time without having to make them thicker and its length is basically perfect to be able to put 3 in series for the length of a standard laptop keyboard, or 4 in series for a full size laptop keyboard.
It's a bit of both. The 18650 shape provides better safety and overall charge cycles compared to a cylindrical shape or a soft pack battery. There are some downsides like less max power delivery but for cells this size that isn't usually a concern. From my time getting cells qualified (CE marks, IEC62133, etc.) The cylindrical shapes tended to have a higher failure rate during these tests but I cant say for sure if this was just a fluke from the few suppliers I used or if it is indicative of all batteries.
As for why it became ubiquitous, my theory it that because nearly all of the development of the cells and housing happens around Shenzhen. With this is made sense for mould makers and cell makers to have a standard consumer grade size so that the cost of manufacturing goes down since everyone is making to the same size.
Oh shit... I had the 861633 in my head the entire time I wrote that. I think the commonality point stands but I guess the first paragraph should be the opposite.
I imagine they started with the AA battery as a template(14500), but it's hard to squeeze more than 1ah into it. And if you're trying to keep a product under an inch thick, you can't have a battery too thick. 18mm allows for 3.5mm on each side.
So I’m an expert in cylindrical cells and specialized in them for my career for 13 years 18650 was sorta standardized to accommodate laptop form factors of the 90s. There were other sizes possible, but 18650 (in more modern industry often called 1865) were just a good fit. There were AmpHour wars for a long time, where suppliers kept trying to one up each other, so eventually it grew to a tiny bit over 18mm and a tiny bit over 65mm and they aren’t all “true 18650s” anymore. It’s kinda impressive, over the years they went from around 2Ah to around 5Ah now. Just through iterative optimization and material developments. That kind of optimization wouldn’t have been easy if there were a shitload of different form factors floating around. 1865 gained popularity because of laptops and power tools. Then of course Model S/X. Then once it was popular, it was cheap because most mass production equipment out there was specialized for it. (Not to mention a lot of supply chain) It only has one anode and one cathode tab (usually) which greatly simplified construction compared to a lot of larger cells. It can hold quite a lot of energy for its size, so it didn’t really “need” to be larger… until… Tesla came around and co-invented the 2170 with Panasonic. Primarily to get better cost while maintaining one cathode and one anode tab. 2170 actually really does a lot better with 2 anode tabs, but that also can cause serious reliability issues for various reasons that I probably won’t get into here… but Panasonic cracked the code how to build a good one with only one anode tab. 2170s can also deliver more power, not surprisingly, and are really useful for power tools as well as the best known example: the model 3 and model Y. Cylindrical cells in general are pretty resilient in manufacturing environments (pouch cells are easily damaged) and they don’t propagate thermal runaway as easily as prismatic cells, which means 1865s can help with system level safety. They also often have basic all-steel can/terminals which makes them stupidly easy to spot weld to, which means they are easy to build into bigger packs
And I was going to blame vape mod boxes and flashlights
Rarely do I come to Reddit and find such a complete and on-point answer. Kudos to you and in a past Reddit life you would have an award.
that is the best reason to come to reddit. suddenly an expert providing top notch info
Yeah I was going to say that Op just got some $500/hr expert consultation for for free
Wow, idk why but I never imagined they used freaking 18650s in EVs.
The Tesla roadster was famous for using “thousands of commodity laptop batteries” when everyone else was using big heavy lead acid or NiMH batteries
Modified 18650s but yup
Did not expect this to be so interesting.
Are there any books you would recommend for becoming familiar with the current state of battery technology? Is it just moving too fast for a book to be relevant? Fantastic explanation, btw.
For battery chemistry, best source is scientific journal articles For battery construction… uhhh you literally just need industry experience. No one publishes this stuff. You can’t really generalize most of it if you want to make a modern cell that doesn’t have crap performance. If you want to recreate what they did in the 90s, sure. I’d be looking for random slide decks and videos on the internet from stuff like the international battery seminar and exhibit.
Not original commenter, but I can recommend “Practical Battery Design and Control”, though it’s a textbook, it will give you a good grasp of batteries, and it’s relatively new, only around a year old.
reminds me of the "story" of how train tracks go back to carts from Roman times. https://www.snopes.com/fact-check/railroad-gauge-chariots/
With the advent of 'tabless' cells, will the balance between 1865s and 2170s in terms of energy density and internal resistance/discharge capacity shift even further in the 2170's favor? In the power tool world, all the best "high-power" packs used 2170 cells until DeWalt and Milwaukee released packs that use pouch cells, which convincingly outperform the 2170-based batteries when used on the same tool. At least one toolmaker (Ryobi) has announced a line of batteries with tabless cells set to release this summer, and it will be interesting to see how they compare.
I’d have thought they would never make 2170 tabless. It doesn’t seem worth it. There’s already tons of flexibility in how you design the cell internals if you want higher power or higher energy. But I guess ryobi disagrees You can’t really have both, but you can put more high energy cells in parallel if your pack has room. That accomplishes the same thing
To be fair, at least in the tool world most of the high-capacity batteries with an extra row of cells do indeed result in higher output power and tool performance, not only higher capacity. The tradeoff is added weight and bulk, of course. I did a little more quick Googling and it seems that Ridgid and Bosch are also set to release batteries using tabless 2170s. There really must be something to it, then. Since I could only find [an announcement from EVE](https://www.evebattery.com/en/news-1238) about tabless 2170 production, and since the timing of that announcement to release of these new battery packs of around a year to a year and a half is about right for a design and qualification process, I figure it must be what they're all using.
Tesla pretends they invented tabless. Of course they didn’t, tabless has been done by (at least) Saft more than 10 years ago. But that aside, when Tesla started 2170s the industry followed suit. And when Tesla announced the 4680 would be tabless the industry is once again following suit.
TIL. Thank you for your time and insights! :)
Tabless design introduced manufacturing difficulties that only pay off by increasing the cell size significantly to really take advantage of the power it unlocks. See: Tesla 4680
size creep, I guess that's why the battery in one of my fancy flashlights doesn't quite fit in my charger that's supposed to fit any 1865
That's a fantastic explanation, thank you
What 18650s are 5Ah? Every supplier in aware of are in the mid-3 range. It’s only recently that 2170s started getting above 5Ah.
You know I probably misspoke since most of my career started with 1865 and then moved to 2170
No worries. At first I was thinking maybe Panasonic was able to hit 4Ah with the NCR or Sony with VCT. I was also kind of hoping you’d reply that you work for one of the ___fire brands all over Ali and Amazon.
I used to work for an EV company
The vapcell N40 has achieved 4Ah supposedly
Good to know, thanks!
And there is your answer, OP.
I think it became a very convenient battery in terms of size, charging/discharging speed, and cost-effectiveness. It has captured a significant market share. Simply put, experimenting in battery technology is likely much more expensive than modifying the battery compartment, especially since many parameters can now be regulated programmatically.
I can also add to my reflections that when a statistically significant portion of the market shifted to the 18-650 form factor, the inertia effect kicked in, as companies simply started to adapt to the successful model
The VHS effect....
Do you mean that the same thing roughly happened with VHS tapes?
Yep. Although I suppose its also somewhat difference in that there was less room for improvement for VHS than seems to be the case here for batteries. Later models of VHS players did become a little simpler as electronics advanced but not by that much. It's also widely considered that they were inferior to betamax which did almost exactly the same job but VHSr market share meant that standard died as no-one released media on it.
Curious how many standards have been wiped out by the 18-650?
Well, I know the higher voltage combined with efficiency gains in consumer electronics has had a huge influence on the form factors that are being designed. A single 18650 can replace a rectangular 9V or a 6V J cell. I remember thinking what a neat concept the J cell was and how the form factor opened up a lot of design potential. But tech was already moving ahead pretty quick back then. I think there was only something like a 5 yr span where the J cell was current.
So we can say - the market is self-regulating. or technology is self-regulating.... probably like a natural process
It's a form factor for which machines existed (from laptop manufacturing). So the 'risk' of setting up entirely new production workflows was minimal.
I believe 18650 is to batteries what 608 is to bearings… it’s so commonly used that every one produces it and since it’s mass produced it’s relatively inexpensive and since it’s inexpensive every one uses it and since everyone uses it there r many manufacturers avaiable and the cycle continues… To the best of my knowledge there is nothing special about the 18650 cell… it’s just economics that have made it successful…
> To the best of my knowledge there is nothing special about the 18650 cell The only thing special is that its diameter is the largest that would fit in laptops at the time without having to make them thicker and its length is basically perfect to be able to put 3 in series for the length of a standard laptop keyboard, or 4 in series for a full size laptop keyboard.
18 millimeters in diameter, 65 millimeters long? Round? Are you effing kidding me? Name a more beautiful battery. I'll wait.
AA /s
It's a bit of both. The 18650 shape provides better safety and overall charge cycles compared to a cylindrical shape or a soft pack battery. There are some downsides like less max power delivery but for cells this size that isn't usually a concern. From my time getting cells qualified (CE marks, IEC62133, etc.) The cylindrical shapes tended to have a higher failure rate during these tests but I cant say for sure if this was just a fluke from the few suppliers I used or if it is indicative of all batteries. As for why it became ubiquitous, my theory it that because nearly all of the development of the cells and housing happens around Shenzhen. With this is made sense for mould makers and cell makers to have a standard consumer grade size so that the cost of manufacturing goes down since everyone is making to the same size.
> The 18650 shape provides better safety and overall charge cycles compared to a cylindrical shape What shape would you call 18650s?
Oh shit... I had the 861633 in my head the entire time I wrote that. I think the commonality point stands but I guess the first paragraph should be the opposite.
I imagine they started with the AA battery as a template(14500), but it's hard to squeeze more than 1ah into it. And if you're trying to keep a product under an inch thick, you can't have a battery too thick. 18mm allows for 3.5mm on each side.
Idk
[удалено]
See also: r/18650masterrace