Cylindrical Lithium Battery: 21700 VS 18650 - DNK Power

There are many sizes of lithium-ion cylindrical batteries, and the number of sizes continues to grow. batteries and batteries are two of the common types of lithium batteries. Both of these batteries are named by the size of their own.

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Obviously, you can find out from the name that these two types of batteries are actually different in size. But they are suitable for the same devices in most cases.

Many people will be torn in the choice of these two batteries in the end which battery is better? Hopefully this article will help you solve this problem.

PROs of batteries:

1.）The energy density of the type battery is higher than type battery.
2.）The cost will be reduced.
3.）The batteries are lighter in weight.
The capacity supported by battery are more than mAh, even some mAh have emerged. Therefore, the larger capacity could help to increasingly prolong the lives of modern devices and to upgrade user’s using experiences.

CONs of batteries:

1.）The larger capacity of the battery needs longer charging times.
2.）technology is unstable and mature. The battery production and processing equipment, technology and so on can not be ready in a day, so now this battery can not be mass production. And not as fast as the development trend of technology.

battery

It has a disadvantage in terms of energy density and cost, but it performs better in terms of standardization, automation, technological maturity and ladder utilization.

Cylindrical batteries, especially , due to their own structural characteristics and the standardization of their models, the level of automation in the production of cylindrical batteries is the highest among the three main battery forms. This makes it possible to have a high degree of consistency, and the yield is improved accordingly. Data show that the yield rate of major foreign manufacturers such as Samsung and Panasonic can reach 98%, while Chinese manufacturers can also exceed 90%.

PROS of battery

1) As mentioned earlier, the monomer consistency is better；

2) The monomer itself has good mechanical properties. Compared with square and soft-packed batteries, a closed cylinder can obtain the highest bending strength at approximately the same size.；

3) The technology is mature and the cost is low, but at the same time, the space for cost optimization has been almost consumed.；

4) The energy of the monomer is small, and the form is easy to control in the event of an accident, but this is also becoming the reason for its replacement (what about the popular saying, those who make you will also destroy you, and those who can’t kill you will also make you strong. The same is true for things)

CONS of battery

1) In the context of electric vehicles, the number of cylindrical monomers in the battery system is very large, which makes the complexity of the battery system greatly increased, regardless of the mechanism or the management system, compared with the other two types of batteries, the system-level cost of cylindrical batteries is high.

2) Under the conditions of uneven temperature and environment, the probability of alienation of the characteristics of a large number of batteries increases. Of course, the reason why Tesla chose at the beginning of the design is believed to be just a helpless choice, because 10 years ago, only cylindrical batteries could be produced in large quantities. Qualified power batteries. On the contrary, the safety and thermal management needs of the battery are the driving force for the development of its powerful electronic control system.

3) The room for energy density to rise is already very small. According to the news in , Chaowei has achieved a monomer capacity of mAh, and the specific energy of the battery is 306Wh/kg.

From a battery performance level:

1.) li-ion battery has larger capacity

Being that the battery is slightly larger, it will also provide more energy/power and runtime. Experimental studies by scholars have shown that the battery has about 5.3 circles of electrodes more than the battery. Taking into account the change in the height of the battery, the overall battery has about 51% more capacity than the battery.One thing to consider here is the mAh of these batteries. mAh’s on batteries will range from up to . On batteries, you can expect mAh’s to range between up to mAh’s. You may see advertising for batteries that claim to have up to mAH.

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2.) battery has smaller inter resistance than battery

For cylindrical cells these parameters correlate with each other. This contributes to the lower performance of high energy cells. Electrode thickness has a possitive influence on cell resistance. battery is thick than battery.

Going from the to the format, the cell resistance decreases noticeably and shows a relatively flatter correlation to anode coating thickness.

The reason is the larger usable coated cathode area in the larger -type cells, especially due to the outer windings of the jelly roll.

3.) battery has lower discahrge rate than battery

Electrode thickness has a negative impact on the discharge rate capability. As we all known that battery is thick than battery.

Cells with thicker electrodes experience higher losses by limited transport, resulting in lower discharge energy and underutilized electrode active material. Thegeneral trend for all tested cell types was found that therate-capability is limited by the temperature on the cell surface due to current flow.

4.) battery has higher energy density than battery

Change cell into cell, battery energy density can be increased by more than 20%. battery power density is better than batteries. According to the current disclosure of Tesla, under the existing conditions, the energy density of battery systems is approximately 20% higher than the 250WH to the original -300 Wh battery system. At the same time, according to the Panasonic lithium battery power test in monomer batteries, the bulk density of its 21,700 battery is significantly higher than that of the cell monomer.

Compared with battery system, battery system cost down by about 9%. Main reasons are as following:

a.Each single lithium battery contains more than 50% more energy than , so the total number of single lithium batteries in use can be greatly reduced.

b. Since the lithium battery has more energy, the total number of parts and facilities required to manufacture the same Wh lithium battery is reduced, which is beneficial to reduce costs.

c. Since the lithium battery has more energy, the total number of parts and facilities required to manufacture the same Wh lithium battery is reduced, which is beneficial to reduce costs.

d. Lithium battery housing, because the diameter of the lithium battery is larger, it can accommodate more lithium batteries, so the shell required for each Wh, the lithium battery is 33% less than the lithium battery, so the shell cost of the lithium battery is lower than .

e. The number of lithium batteries with the same Wh number is reduced by 33%, so the requirements for the injection and sealing process are also somewhat reduced, and the cost is somewhat reduced.

f. Similarly, with the reduction of the overall number of lithium batteries, the requirements for chemical facilities have also been greatly reduced, increasing the rate and reducing costs.

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I just saw a short video from Battleborn stating they use cylindrical cells vs prismatic cells. The benefit being they can be fully discharged 100% without affecting life of their batteries. They say prismatic cells can advertise cycles at 80% discharge but in reality is closer to 900 cycles at 100% discharge. They say Battleborns with last - cycles at 100% discharge.

I am always a little skeptical of companies telling me why they’re better so I would like to know this groups thoughts…

. They say Battleborns with last - cycles at 100% discharge

100% discharge may mean down to their BMS cuttoff @20% ??
Probably because they are based in the USA they need to be more honest with their stated battery capacities verses cycles and have their batteries perform to what they are rated.... 100ahr battery needs to supply 100ahr, So they use 120ah of cells. A 100% discharge(100ahrs) down to bms cut off still leaves 20% charge in the batteries for the cycles stated.

"I am always a little skeptical of companies telling me why they’re better "....yes, always read the fine print How much are bus bars going to cost connecting so many small cells? I think there's some costs you're not factoring in building a pack with the small cells. I would probably go with prismatic simply because they're so easy to deal with. I thought prismatic cells advertised like eve 100% discharge for up to or 3,000 cycles and still keep 80% capacity. I don't understand why anybody wouldn't push these cells to their Max.

How much are bus bars going to cost connecting so many small cells? I think there's some costs you're not factoring in building a pack with the small cells. I would probably go with prismatic simply because they're so easy to deal with. I thought prismatic cells advertised like eve 100% discharge for up to or 3,000 cycles and still keep 80% capacity. I don't understand why anybody wouldn't push these cells to their Max.

Eve advertises cycles using 80% of the soc, the prismatic cells last longer (on average double) than the cylindrical ones, the advantages of the cylindrical ones are summarized in the possible installation position that does not create any problem

They are 100% as well, 2.5 volt cut off.

yes, but there are cycles, the point is: respect the ideal temperature conditions, which is definitely impossible when installing in particular situations such as RV vehicles. Therefore: respect the 80% soc and try to make a fixation as close to the famous 300kgf to extend the life of these batteries Most primatic LFP cells are thick electrode design. Thick electrode means the thickness of graphite negative electrode and positve LFP electrode are 110 to 150 um thick. This yields the most AH capacity per unit volume and weight but cell suffers from ion starvation above about 0.5CA cell current caused by the thick electrodes. This increases terminal voltage slump and internal cell heating accelerates above 0.5 CA cell current.

Most cyclindical cells are made with thinner electrodes design in 50 um to 100 um thickness. This means more layers are required for same AH rating as capacity is dependent on amount of graphite and LFP material. More layers mean more copper foil, aluminum foil, and electrolyte. This costs more, takes up volume, and adds weight. Extra metal foil benefits are lower contact resistance and better heat dissipation. Cylindrical cell with thin electrode allow high peak cell current with onset of electrode layer ion starvation at a much higher current. This also helps at cold temps where ion migration rate slows down.

Prismatic cells with thick electrode design.
+ Most capacity per unit volume and weight
+ lowest cost
- lower peak discharge current
- less ability to dissipate internal cell heating

Cylindrical cells with thin to moderate electrode design
+ higher peak current discharge rate
+ ability to dissipate internal heating
+ better cold temp performance
- AH per volume/weight
- higher cost

There is really no difference in damaging effects of, depth of discharge between thin or thick electrode designs. Both will grow metal dendrites if left for moderate time below 1.0 vdc and both will have severe electrolyte decomposition if discharged below about 0.1 vdc or charged above 4.3 vdc. I wanted to thank you for the detailed response. I wasn't aware of some of those differences.

I personally went with lifepo4 cells because I got a good deal at the time and the one thing you really don't have to worry about with cylindrical cells is dealing with any type of compression.

In my scenario, I figure in ten years I could be left with an 8s system that has one bad 280ah cell OR I could have five failed and twenty still working fine. One bad 280ah cell could screw up my entire system and a new one would perhaps take days to arrive and then it would be a different capacity and lifecycle than the other cells in series. The I could rearrange as needed with a bit of work.

I don't hear people mentioning these benefits all that much, and certainly it is easier to just wire up 8 big cells vs hundreds of cells.

It didn't hurt that battleborn and others use cylindrical cells and have decent warranties.

I just saw a short video from Battleborn stating they use cylindrical cells vs prismatic cells. The benefit being they can be fully discharged 100% without affecting life of their batteries. They say prismatic cells can advertise cycles at 80% discharge but in reality is closer to 900 cycles at 100% discharge. They say Battleborns with last - cycles at 100% discharge.

I am always a little skeptical of companies telling me why they’re better so I would like to know this groups thoughts…

I call BS on their claims. The format of the cell has nothing to do with the longevity.. well.. almost nothing.

Cylindrical cells do have one minor advantage, but its so minor as to be insignificant, and it only applies in certain applications.. because of the cylindrical shape, they are just ever so slightly better at dissipating heat.

Beyond that, cylindrical cells tend to blow up because of the way they can build and retain pressure, while pouch cells tend to flame out with less force.

These companies make all kinds of claims to boost sales.. i’m kind of reopening a fairly old thread. But recently I discovered an article talking about the advantages of cylindrical cell versus prismatic cells. I have particular interest in this subject since completely by chance I ended up with a set of four batteries that have cylindrical cells inside. They make up a 48 V battery that I use in my camper.

Cylindrical cells can be placed in any orientation with no adverse effects

Cylindrical cells can be charged at colder temperatures than prismatic cells.

Cylindrical cells have a higher c rate than prismatic cells.

Cylindrical cells have better cycle life at full depth of discharge than prismatic.

Cylindrical cells have more cycle life than prismatic cells

Cylindrical cells stay cooler than prismatic cells.

I’m wondering if any of these claims are true and to what extent. Is there any proof pro or con. yes the cylindrical ones have a higher internal resistance, fewer life cycles, the discharge in terms of C is not very different from that of the more performing prismatics and the charging temperature depends on the chemistry so it is the same. also cylindrical are often made by small companies that do not have quality control such as companies such as Caltl, Eve, rept, Calb etc.

yes the cylindrical ones have a higher internal resistance, fewer life cycles, the discharge in terms of C is not very different from that of the more performing prismatics and the charging temperature depends on the chemistry so it is the same. also cylindrical are often made by small companies that do not have quality control such as companies such as Caltl, Eve, rept, Calb etc.

I have been trying to find documentation for the expected life span compared with each other and so far I have not found where they have been tested against each other. Battleborn ( one of the best known lithium batteries built in the USA) uses cylindrical cells in there batteries with excellent results but the cells they use are probably better grade than the batteries I have and they do extensive testing and balancing before assembling the batteries. The internal resistance of the batteries I have can’t be very high as they charge at 40 amps until they have around 6 amp hours to go and then gradually taper back until full.

I have been trying to find documentation for the expected life span compared with each other and so far I have not found where they have been tested against each other. Battleborn ( one of the best known lithium batteries built in the USA) uses cylindrical cells in there batteries with excellent results but the cells they use are probably better grade than the batteries I have and they do extensive testing and balancing before assembling the batteries. The internal resistance of the batteries I have can’t be very high as they charge at 40 amps until they have around 6 amp hours to go and then gradually taper back until full.

the smaller batteries are as Ah the greater the internal resistance I know that this thread is old but I would hope that those who are inclined to troll me will consider how I got here before acting on your instincts.
After looking into the idea of building a pack of Samsung cells from this address.:
. I've decided that the discharge curve of prismatic cells is more advantageous for my purpose. If I had needed periods of extreme rates of discharge, I would have gone with cylindrical.

I've decided that the discharge curve of prismatic cells is more advantageous for my purpose.

this is related to the cell chemistry which is likely lifepo4 for the prismatic cells
the ones you linked are very unlikely to be but they don't make it obvious, probably LiCoO2

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