Analysis of cylindrical lithium battery advantages and common models
Analysis of cylindrical lithium battery advantages and common models
1. Definition of cylindrical lithium battery
Cylindrical lithium battery is a kind of lithium ion battery, its shape is cylindrical, so it is called cylindrical lithium battery. The structure of a typical cylindrical battery includes: casing, cap, cathode, anode, separator, electrolyte, PTC element, gasket, safety valve, etc. Generally, the battery shell is the anode of the battery, the cap is the cathode of the battery, and the battery shell is made of nickel-plated steel plate.
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2. The development history of cylindrical lithium battery
Since Tesla's battery day in September proposed large cylindrical cells, large cylindrical cells have once again become the focus of the battery industry in the market. In addition to Tesla, China's leading cell factories have also begun to invest in the mass industrialization of large cylindrical cells.
According to the data shown by Tesla, the large cylindrical lithium battery will increase the energy by 5 times on the basis of the cylindrical cells, increase the mileage by 16%, and reduce the cost by 14%. Its technical temptation is very significant. However, during the period of rapid development of China's new energy vehicles in the past, first-line brands including CATL and BYD all focused on the technical route of square cells. At present, the industrialization of power batteries is basically based on square batteries, and even Tesla has purchased square batteries with a capacity of about 161Ah in China for use in one of its models.
From a technical perspective, both technical routes have their own value and advantages. In a complex battery system, although batteries account for the highest cost, in terms of safety and cost performance, we cannot only focus on one dimension of batteries. For example, Tesla has industrialized and applied the cylinder and to electric vehicles with energy exceeding 70KWH through advanced management system design. In fact, it is using advanced management to optimize the performance of the battery system.
3. Relative advantages of cylindrical lithium battery
● Advantages of small capacity flexibility
Due to size and process limitations of cylindrical cells, the capacity of a single cell is usually small. For example, ternary battery 3.5Ah, iron-lithium battery 6Ah, iron-lithium battery 15Ah, iron-lithium battery 20Ah, etc. Aside from electric vehicles and large-scale energy storage markets, in other fields, such as AGV, portable energy storage, and home energy storage, the capacity of single-module batteries is usually not very large. In practical applications, the large-capacity square cells positioned for automobiles and large-scale energy storage do not necessarily exactly match the market demand, including size and capacity.
The small-capacity cylindrical lithium battery can be connected in parallel to meet the battery module capacity needs of certain market demands. For example, the two types of lithium batteries 24V60Ah and 48V30Ah used in AGV cars are relatively common needs. Three types of cylinders, , and , can be combined in parallel to form the required 60Ah or 30Ah modules. At the same time, there are more flexible operation possibilities in the space structure to meet the design requirements of different models.
● Cost advantage
In the production and manufacture of all lithium-ion batteries in lithium battery companies in the world, the process standardization of cylindrical lithium battery is the highest, and it is also the earliest commercialized battery. The assembly efficiency is significantly higher than that of square batteries and pouch batteries. The winding process of cylindrical batteries has reached the level of 200PPM with the gradual improvement of automation. Even though the efficiency of large cylindrical lithium batteries is slightly lower than that of traditional / cylindrical cells, it is much higher than the efficiency of stacking or winding processes of square cells and pouch cells (usually around 10PPM).
The reason for the small capacity of the cylindrical lithium battery is that the strip-shaped continuous pole piece after coating is cut into strip-shaped small pole pieces, and the miniaturization of the pole piece can improve the utilization rate of the entire pole piece material. Usually under the same screening criteria and automation level, the material utilization rate of cylindrical cells is 3-5% higher than that of square cells.
● The heat dissipation effect is obvious
Lithium-ion battery fires are all caused by thermal runaway, and the spread of thermal runaway is also the main concern of battery system safety performance. Cylindrical structure is the most likely solution to thermal runaway, while square and pouch structures are basically unsolvable. The low capacity of a single cell causes thermal runaway to release less energy, which is different from high-energy, large-capacity square cells or pouch cells. At the same time, with the gradual improvement of material safety, the heat release caused by thermal runaway is reduced, which significantly increases the safety of the battery system.
The curved surface structure of the cylindrical lithium battery limits the heat transfer process between the cells to a certain extent, and has a certain positive effect on the spread of thermal runaway. However, square batteries and pouch batteries are basically unsolvable in this regard. Furthermore, with the promotion of the full-tab process, the heat transfer of cylindrical cells is more on the upper and lower end caps of the cells, and the heat transfer on the curved surface will also be reduced.
The above is some analysis and thinking based on different application scenarios of lithium batteries with different structures. Although the focus is on analyzing the advantages of cylindrical lithium battery, it is undeniable that cylindrical cells have shortcomings in certain application fields. At the same time, it is also necessary to objectively understand the own advantages of square cells and pouch cells.
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4. Common cylindrical lithium battery models
With the development of lithium battery technology, there are more and more types of cylindrical lithium battery. Cylindrical lithium battery are divided into lithium cobalt oxide, lithium manganese oxide, and ternary materials. The three material systems have different advantages. Let's take a look at the models and specifications of cylindrical lithium battery. Cylindrical lithium battery is usually represented by five digits. Counting from the left, the first and second digits refer to the diameter of the battery, the third and fourth digits refer to the height of the battery, and the fifth digit refers to the circle. There are many types of cylindrical lithium battery, the more common ones are , , , , , , and so on.
● battery
The battery is a cylindrical lithium battery with a diameter of 10mm and a height of 44mm. It is the same size as what we often call the 7th battery. This battery capacity is generally small, only a few hundred mAh, and is mainly used in mini electronic products. Such as flashlights, mini stereos, megaphones, etc.
● battery
The battery is a cylindrical lithium battery with a diameter of 14mm and a height of 50mm. This is also the size of what we have always called the AA battery. This kind of battery is generally 3.7V or 3.2V. The nominal capacity is relatively small, a little larger than the battery, generally mAh, and the discharge performance is superior. The most important application field is consumer electronics, such as wireless audio, electric toys, digital cameras, etc.
● battery
The battery is a cylindrical lithium battery with a diameter of 16mm and a height of 34mm. Due to its shorter height and relatively small capacity, this kind of battery often appears in glare flashlights, LED flashlights, headlights, laser lights, lighting fixtures, etc.
● battery
The battery is a lithium-ion battery with a diameter of 18mm and a height of 65mm. Its biggest feature is that it has a very high energy density, almost reaching 170 Wh/kg, so this battery is a battery with better cost performance. Most of the battery store we often see are batteries, because it is a relatively mature lithium-ion battery, and the system quality is stable in all aspects. It is widely used in occasions with a battery capacity of about 10 kWh, such as mobile phones, notebook computers and other small electrical appliances.
● battery
The battery is a cylindrical lithium battery with a diameter of 21mm and a height of 70mm. Because of its larger volume and greater space utilization, the energy density of the battery cell and the system can be improved, and its volumetric energy density is much higher than that of the battery. Widely used in digital, electric vehicles, balance cars, solar energy lithium-ion battery street lights, LED lights, power tools, etc.
● battery
The battery is a cylindrical lithium battery with a diameter of 26mm and a height of 65mm, with a nominal voltage of 3.2V and a nominal capacity of mAh. This kind of cylindrical lithium battery has the characteristics of excellent capacity and high consistency, and has gradually become a trend to replace batteries. Many products in power lithium batteries will also gradually favor it.
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Cylinderical LiFePO4 cells? | Endless Sphere DIY EV Forum
Today, it is these cylindrical Lithium Iron Phosphate cells: https://www.alibaba.com/product-detail/High-efficient-H-3-2V-30Ah_.html?spm=a.details.deiletai6.5.241a545b37uqsb
So these may not be new but they're new to me and I have not seen anybody build with them them before.
Does anybody have any experience with these? The alibaba listing does not say the max peak and continuous discharge capacity and I would like to know that. It also doesn't say the dimensions [edit: I see it now. They're , or 48mm x 270mm). I have Micah Toll's book on diy lithium batteries and he says that LiFePO4 cylinders are made by Headway in the and sizes, but the book is 3 years old now.
The reason I would want cylinders over prismatic cells is because I could built the battery pack into a custom shape. I want my battery box to be very asthetic. The cells also have bolts for terminals so installation will be much easier than ion cells. I would need 23 of them to get 72v. Here's my mockup: https://www.vintagehondatwins.com/forums/showthread.php?-CA160-EV-Conversion&p=&viewfull=1#post
Thanks! At that price, I wouldn't mind paying a little more for some assurance. Here's another source - https://www.batteryspace.com/lifepo4-s-cell-3-2v-15-ah-150a-surge-rate-48wh-with-6m-screw-terminal---un38-3-passed.aspx - but they're half as much capacity so I'll need twice as many. But look at that price! $40 each for a total of $1,840. The alibaba ones would only cost me $230. At that price maybe it's worth the risk.
neptronix said: Just keep in mind that headways aren't much more energy dense than lead acid batteries. They hold a third of the energy of the best non-lifepo4 lithium cells on the market today.
Only a good choice if safety trumps all other considerations.
Genuine Headway cells have better power density than most, with easier and higher-ampacity pack assembly methods than almost anything. They come in higher and lower energy versions, with inversely proportional maximum current ratings.
I haven't used Headways, but my own e-bike packs are made from automotive cells that sacrifice energy density for power density, ease of assembly, cycle lifespan, cost per kWh, and pack simplicity compared to s. I wouldn't mind having more range or lighter pack weight, but I wouldn't want to trade off the qualities I enjoy now in favor of those things. Genuine headways come in at around 80whrs/kg ish. I had a pack with them a decade ago. The things are effin' huge. About 3 times larger than 150whrs/kg lipo. 200-250whrs/kg is the current standard for energy density.. so this is a far cry from good.
I literally just sent the pack to a recycler because it didn't even remotely perform up to the discharge spec either.
They're also rather expensive per whr.
I agree that a large pack with s is a pain in the ass to build. Building a pack with 's cuts the number of cells needed in half. That's a good in between solution.
john61ct said: The only cylindrical LFP worth a hill o' beans are A123
I just ordered some of those. Their energy density is pretty low-- even lower than the low energy density automotive cells I'm using now. But their power density is phenomenal.
They have the same problems as any cylindrical cells lacking threaded terminals, in terms of difficulty of assembly and being limited by their connections more than by their cells' capabilities.
999zip999 said: I was looking at these
https://batteryhookup.com/products/100-brand-new-lifep04--3-2v-mah-cells
They also have the 8ah headway s at 16.00
Lifepo4 is big and heavy my A123 20 ah pack lasted 7 years charge cycles. No BMS just bulk charge.
I order a Samsung 40t 30 amp cell triangle pack 20s 6p. 180 amps on paper BT BMS
I agree 100%. I use A123 ANRM1-B LIFEPO4 cells for EBike builds. They can provide 50A continuous per cell, 120A burst. Being LIFEPO4 chemistry they can be cycled 3x more than typical Li-Ion cells. Battery Hookup sells those cells around $1 each. They are listed as used but all the ones I have received test out better than 90%. You could build a 10Ah 72v 24s4p pack for a little over $100. It's a no-brainer. The only drawback is that they do take up some extra space since they are cells.
Hosedragger said: I use A123 ANRM1-B LIFEPO4 cells for EBike builds. They can provide 50A continuous per cell, 120A burst.
I recently bought some of those; I have yet to figure out how best to use them. I have seen their impressive cell specs, but I've never seen a plausible method for getting that amount of juice out of them. The modules I bought are fused 70A for a 4P pack, suggesting that their real ampacity (with an engineered bus) is something less than 17.5A/cell. For a homemade bus, I'd derate them beyond that.
Their energy density is low even by LiFePO4 standards. I made a 34s10p pack out of these A123 cells and can get over 600A out. And in a kart track my pack last about 10km (using 2kwh) of heavy acceleration and braking (i'm not using regen).
https://endless-sphere.com/forums/viewtopic.php?f=14&t=
Yes they are heavy (about 37kg is my pack and has 2,5kwh of energy).
My lipo pack that weights about the same 37kg has 3,5kwh of energy. Can't really compare the density of the tiny cylindricals to high Ah capacity prismatics where 40Ah per cell is considered small.
Getting all the pack capacity you need from a single string (no paralleling) is the ideal, but with most "bike" designs the weight and pack space dimensions are severely limiting.
My ideas for pure utility cargo / tandem design give more flexibility, but it seems most people are looking for greater speed, agility sporty "fun" factor.
Too bad no one makes cylindrical cells at say 7Ah with a round cross section of say 3-4" ?
I bet one day we'll see greater merging of the energy storage and structural framing tubes
john61ct said: .......7Ah , with a 3-4” cross section ??..
Too bad no one makes cylindrical cells at say 7Ah with a round cross section of say 3-4" ?
.. that would only be about 5mm thick !
Very difficult to “wind” that jelly roll...and even tricky to make as a pouch !
Why would you want that format ?
A123 used to produce an 8Ah , 32mm dia , high C rate cell with screw terminals.....but no longer available.
Hillhater said:Just spitballing, you including the protective outer shell?john61ct said: .......7Ah , with a 3-4” cross section ??..
Too bad no one makes cylindrical cells at say 7Ah with a round cross section of say 3-4" ?
.. that would only be about 5mm thick !
OK then higher Ah, down to say 2" diameter.
Or a circular pouch format?
Whatever it takes to optimise for a single cylinder pack, no paralleling required, go to 20Ah by expanding the diameter, not length.