Tesla chose the 21700 because the lack of top tier manufacturers making mass 26650s. I think current production rate of the top manufacturers exceeds 1B 18650 cells / year, while 21700s were already produced in enough quantity for power tools and the additional volume can count a lot.
As for the cooling, from a pure airflow perspective, everything should be fine if properly constructed. Of course, cooling a thinner element is easier than cooling a thick one, but the the heat generated for a similar power drain will be higher for the thinner cell, so no real gain there.
I don’t know if Tesla stated the maximum temperature that is allowed for the used batteries, but I tested an electric car with custom 26650-based pack and there was no overheating heating whatsoever after a 25Km continuous run, same as for Samsung Q cells, while for Sony V3s there was some heating but within the recommended spec limits of the cells.
What do you mean ?
Didn’t the S/X used Panasonic 18650s ?
Yes, they can build their own like for model 3 but that would not be viable for mass production.
PLB makes 26650s, and while their actual market is a ¯\_(ツ)_/¯ to me, for their 50A and 55A cells this is what they claim:
PLB INR26650-55A 3.6V 5500mAh lithium ion cell is high energy li-ion battery for power application, which has been passed The National Mandatory Inspection and widely used in electric motorcycle, elctric tricycle, lead acid replacement, AGV, power station, ESS, PV street light and so on with high safety on design, high consistency, high reliability, and long cycle life on performance. -> Here.
INR26650-50A 3.6V 5Ah NiCoMn(NCM) battery cell for Motorcycle and Tricycle has been successfully qualified with The National Mandatory Inspection , which widely used in electric buses, electric logistics trucks, electric special vehicles, power station, energy storage system and so on with high security, high consistency and high reliability characteristics. -> There.
It looks like PLB is heavily focused on LiFePO4 development, and they're in China. Don't know how much improvement is to be expected. They also definitively won't be in the media.
Tesla decided to foster development of a new cell size just because that fitted their interests. They didn't have any interest in 26650 development, that wouldn't have allowed them to file new patents and blah blah blah.
Yes, early vehicles used the Panasonic 18650B 3400mah, but several years ago they were evaluating new sizes and started building the Gigafactory. They started out with the plan to build 20700 and then decided 21700 would be better. Once they built their own factory they don’t care about 26650 availability.
Maybe you mean post 211? I still have not heard of any OEM vehicles (like passenger cars) using the 26650. Of course, I am not in this field so there is a lot I don’t know.
PS, those quotes from PLB sound like typical marketing speak to sell batteries. Are they saying their cells can be used for those things or that they are used for those things. There is a big difference. I would love to learn about OEM vehicles using the 26650.
Store 133859 sold me 4 blue “liito-kala” 26650s that tested well below advertised capacity. I used two different testers and checked 4 batteries. I’ve been using them and they all OK, but not as good as the black and gold LiittoKala cells I bought elsewhere.
The sticker on the pink 21700s from store 133859 has links for both LiitoKala websites!
Is 133859 selling LiitoKala knock-offs? Are they a different (mainland vs. HK) division? I don’t know. I’m not buying anything else from store 133859.
http://liitokala.com.cn links to AliExpress store 217753, liitokala Official Store ( liitokalahongkong.aliexpress.com ) Store 217753 sold me black and gold 26650 Lii-50A that meet advertised specs. As far as I can tell they are the same as the ones tested at the top of this thread. That was several years ago though. If I want more LiitoKala 26650’s I’d buy from them again.
Thanks, I have placed an order with that store… ive since seen at least 5 more ali stores purporting to Liitokala affiliated
You have
Liitokala Factory store
Liitokala Direct store
Liitokala Battery Charger Officiail Store
Liitokala OfficialNO.2 Store (lol at this one)
Liitokala Official Flagship Store
I ordered from
Store No.217753 both 26650 & 21700
Sadly before i realised the game i had already ordered some from Store No.1823237 (liitokala Direct Store) Pretty sure I’ll be getting screwed on those.
Neither order has arrived yet but i will report capacity when they do
PLB must sell a lot for the inland market. I do not really know, but they manufacture the 50A and 55A cells and these are very easy to purchase everywhere in AliExpress (with different rewraps, of course) and Alibaba (example). This means they're in full production, and certainly they're not mainly manufactured to fill the shelves of the LiitoKala seller gang so I am sure large volumes of PLB cells go somewhere else.
If I were to purchase from them I wouldn't be screwed, this is a sure thing. And I've never lost a dispute.
And increased fire/explosion safety. Though they aren’t Li-Titanate-level of cycles, I’m told that LiFePO4 offers more cycles than standard cells. Most of the people here know far more about batteries than I, but I think that LiFePO4 also reduces the cobalt demand as well, though obviously with reduced energy density. They are no panacea.
Actual chemistries today are more complex than I understand, though.
Also, LiFePO4 can be overcharged to a surprising degree without damage, which is quite different than our standard chemistries. From what I’ve seen, LiFePO4 cells could be safely charged to 4.2V. There is no capacity advantage when doing so, however, as the cell is effectively saturated by 3.6V with the bulk of the charge achieved even by 3.4V.
This is interesting when replacing flooded lead-acid batteries, as a 4S pack is fully charged by 14.4V and should handle up to 16.8V without damage. Regulation is still needed, however, as alternators can output up to 18V when extremely cold. This wouldn’t damage the pack within the few seconds that this usually occurs, but regulator failure could harm the pack. At least it shouldn’t explode or burn.
Which blue ones? The blue/cyan 5000mah are older, but good cells. The blue 5100mah seem to be a random variety of 26650 they get from different places. Their capacity measurements from battery chargers are all over the place. Sometimes higher, sometimes lower.
I’m guessing by the overly high reading it’s the 5100mah.
First of all, that measurement isn't a test. It is a standard charge measurement, which The_Fat_Controller initiated with the cell discharged to some point. :???:
On the other hand, analyzing chargers are far from being laboratory equipment. They measure differently in all their slots. I myself have taken the time to properly average my Lii-500 measurements and obtain compensatory channel indexes. On top of this I believe it measures a little bit below Henrik's setup.