18650 vs 21700 batteries - Knivesandtools

Difference in capacity of the and the batteries.

The main difference between the and the batteries is the size. Because the battery is a lot bigger than the it also has more capacity. The maximum capacity of an battery is namely around mAh, while the battery can produce up to mAh. More capacity, of course, means more burning hours. As such the is perfect for long-term use if you cannot charge your battery in between. Think, for instance, of a police officer who needs to handle traffic all night. Depending on the type of light you use, you need to pay attention to the brightness of your light to get through the night, when using an battery. This will be a lot easier with batteries.

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More room more power

In addition to the difference in capacity the larger size of the is also an advantage. Because it is larger there is more room to reinforce the cooling and power characteristics of the battery. batteries namely have a capacity of up to watts. The stops at 800 watts. The difference in capacity ensures that the devices that use a battery have more power. A flashlight with a battery will therefore burn longer and brighter than a flashlight with a battery.

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Advantages of the batteries

When you take all information listed above into account it looks like the battery is superior. On paper this is true, but the remains a strong alternative. An battery is a little more compact and lighter. The battery is also more affordable. The amount of flashlights that can handle an battery is bigger and the battery is a lot more affordable than its bigger brother. In terms of power and capacity, the battery is more than enough for the average use of a flashlight.

Conclusion

If you are looking for a good rechargeable battery for your flashlight we have got you covered. Whether you go with the larger or the smaller battery. We have a wide selection of both of them. Find the right battery on our battery page.

If you want to learn more, please visit our website What Is a Battery.

I´m planning to build a 72v 20ah (only around 20ah due to limited space). I have never build a battery pack before so I have been doing quite a lot of research but I can´t seem to figure out the best cells to use.

I´ve been looking at Samsung 40t cells because a lot of people recommend them and because I will be able to draw a lot of amps from a batterypack made by these cells using the copper nickel sandwich method. However if I use these cells (or any other / cells) I will have to invenst in a spotwelder. I have been looking at a kWeld with the Turnigy lipo battery recommended on the kWeld website and the total cost for welder and battery including freight cost will be around 400 euros. Since I don´t know how many battery packs I will be building this seems a little bit expensive and it got me thinking that there might be other ways of building good battery packs without spot weldning? I´ve seen people using eig c020b cells for example with bus bars that screws on to the cells. Eig c020b seems impossible to find and order but maybe there are other similar cells? I have been looking at some Lifepo cells that also allows bus bars to be screwed in place but it seems hard to find Lifepo cells that are as space efficient as the Samsung 40t? Another thing is that I live in Europe so I would prefere a EU (or possibly a Chinese) supplier.

Any help is appreciated! To help select cells, we need to know what the battery needs to do for you.

How much capacity is required? (not the 20Ah you note that you're limited to, because with different cells that might be a different number)

How many amps peak will your system draw from the battery?

How many amps continous will your system draw from the battery?

What are the measurements of the space you have to put it into?

Are you willing to use alternate locations / mounting methods than whatever you've presently settled on?



Some other notes:

--Most pouch (flat) style cells (not the plastic box style like CALB / etc, but the ones like the EIG, Leaf, etc) will be less volume for the same amount of cell, because all of the cylindrical cells will leave an unavoidable gap between each other that is just air. So generally flat cells will fit more battery in the same space than cylindrical cells, as long as your space is a box-shaped space that accommodates that type of pack (where cylindricals can be rearranged in a number of shapes that larger flat cells can't do efficiently).

All the EIG C020 cells will be a little on the older side (AFAICR they haven't been made in a while; mine are over a decade old, I think), and though they do last a long time, all cells do degrade with age. If you do want some NOS unused cells, Jimbob01 has a thread in the items-for-sale-new section; he's in the UK so if you're not it may cost quite a lot to get them shipped to you (probably more than the cells cost). They *are* nice cells, easy to DIY with.

There are plenty of similar cells out there, though not many have premade cell holders and interconnects from the manufacturer like EIGs that make them very easy to DIY with. But as long as they have long enough tabs, there are quite a few ways to clamp them together without soldering or welding, many of which are in various threads around this forum. Some are titled with A123, JonesCG has at least one thread with smaller cells in very large packs for motorcycles/racing/etc, etc.

There's plenty of Chinese Li-Ion / LiPo flat pouch cells out there from Chinese vendors; the catch is finding a cell that will do what you want *and* that you can actually be sure to get from whcihever vendor you choose as actual new top-grade cells. There are numerous places selling non-top-grade cells as if they were, some of them literally recycling garbage cells and even remarking them as different brands / models than they really are (a big problem in stuff), so you have to vet whatever vendor you use to be sure they really will sell you the real thing you're after (or be sure you don't care and will just use whatever you get).


Note that flat pouch cells will generally need some form of physical compression across the flat faces of the end cells of a stack, yo'ull need the specs for how many lbs/sq in from the cell manufacturer to do this "right", to ensure that they don't puff up while in use (charging or discharging). If they do puff up, they're generally damaged and don't perform as they should (and potentially are a fire risk, but mostly just performance issues), and you'll end up replacing them to fix that. There's info on this in the various pouch-cell build threads, among others.

Cylindrical cells don't need that because their casings do it for them.