Nitecore 21700 confusion

[Mx1252]

I just ordered a nitecore new P12. It comes with the 5000mah 21700.

However looking at a nitecore mh10 that is also "21700" light. However comes with 4000mah 21700.

are they different physical size ? Perhaps being new to this I didn't realize 21700 is not a standard.

The batteries are different model numbers. I'm confused. I would have liked to use same batteries on both lights.

Thanks.

 

[bigburly912]

To simplify this. It's the same type of battery. mah is just like a different sized gas tank in a car. It's how long that battery is going to run the light. A 4000mah battery will run slightly less amount of time than a 5000mah. Hope that helps.

 

[ScapegoatUmi]

What he says is true.
The 21700 is the size of the gas tank.

BUT - the same size tank can hold different amounts of mah. There are other criteria that affect the bottom line.
Longevity - how many cycles you can get
Amp draw - how many amps can be given continuously
mah - how many amps are inside when fully charged


Another way to think about this is:

They construct internally to handle higher amp draw vs more capacity. To have high capacity AND high amp draw means more expensive components, and tighter tolerances. These ladder cells usually do not have as many life cycles, exponentially if not a high quality manufacturer.

I hope thats not worse


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[Hooked on Fenix]

Nitecore has 21700 cells rated for a 5,8, or 15 amp drain at a capacity of 4000 and 5000 mAh. They also have each option made normal button top, proprietary, and USB rechargeable. Make sure your light has the higher drain batteries if it's much over 1000-1200 lumens. Be careful to get the right cell for your application because they do have some major differences.

 

[Mx1252]

Thank you all for the help. I replied earlier but seems my posts are still in mod review so trying again. .

I had assumed that all sizes (gas tanks as you say) would be the limiting factor and at least the intention would always be to use to the fullest. As you note, it sounds like the cost and complexity of high draw / capacity do bring some compromise

The cost difference on these 2 nitecore 4000/5000 are quite close so also assume all would choose the higher.

It's mainly good to know that the 21700's will both work. I had a moment of "don't tell me there are 21700's that are various physical sizes". But seemingly not.

it's definitely exciting to come back to flashlights after years of cr123's and see all this technology.

thanks again.

 

[DIWdiver]

Those numbers indicate the NOMINAL size. The first two are the diameter in millimeters, the second two are the length in millimeters, the last zero is generally (but I think not universally) agreed indicates a cylindrical (round) cell.

However, there are differences. My experience is mostly with 18650 cells, but I assume the same will apply to 21700 cells too.

Some cells are slightly longer or shorter than the nominal size. They can also be slightly larger or smaller diameter. The basic cells are generally pretty close, but then there's what you add to the cell. The first thing would be a plastic shrink wrap. These are generally pretty thin but can vary slightly in thickness. The next thing you might see is a 're-wrapped' cell, where a reseller has added a second shrink wrap over the first, to re-brand the cell.

If a reseller has added a button top to a previously flat-top cell, that will increase the length. This will almost always include re-wrapping the cell.

Adding a protection circuit to a cell will add even more length, as you need to add a circuit board with components to one end or the other. Usually this is on the + end. But the protection circuit needs connections to both ends of the cell, so there will generally be a metal strip running up the side of the cell. While the cell construction doesn't really require it, this is normally between the inner and outer wraps, so while you could argue this doesn't increase the diameter of the cell, it increases the diameter of the hole needed to fit the cell.

I doubt you'd ever encounter it, but the absolute worst case would be something like an already large cell, re-wrapped with button top added, then protection added with button top. This could easily add 1mm or more to the diameter and 4mm or more to the length. There are definitely cases where some cells fit the device and some cells don't.

If you are looking at basic cells from the manufacturer, you are generally pretty good. It's when you start looking at re-branded, button-top, and protected cells that you have to start paying close attention to whether the cells you are looking at will fit your device.

 

[HKJ]

Those numbers indicate the NOMINAL size. The first two are the diameter in millimeters, the second two are the length in millimeters, the last zero is generally (but I think not universally) agreed indicates a cylindrical (round) cell.

No, the last 3 digits are the length in tenths of a mm.
The size is for a basic cell and is usually well within +/-0.5mm.
When button top or protection is added to the basic cell it will be longer and a extra wrap layer (and optionally a connection for the protection) will make it thicker.

Some lights will only work with button top cells, due to a mechanical polarity protection. There may also be issues with the length, some light requires a longer cells, other may not fit a long cell. A few lights has a very tight fit in the diameter and cannot handle any extra thickness.

 

[Mx1252]

This is great. Super helpful. I really appreciate it. One add on if possible ....
How do I know the amp draw capability ? Initially i'm using the recommended nitecore brand with nitecore.
But as you said...I will need to aware of the capability of future cells to lights. Is it a clear spec or more a user feedback / spotty depending on manufacturer ?

 

[ScapegoatUmi]

....
How do I know the amp draw capability ?

Most cell advertise the amp draw capability, some give 2 numbers. With 2 (as in 40/30) the first larger number is max, but not sustainable. The second lower number is sustainable. Good cells will have a "C" rating printed on the wrapper. The sustainable amp limit is the C rating times the capacity, or mah.

That black and yellow 40, thats bs. The Red AW 15c, with 800mah. 15x800=12000mah, or 12amps. The Olight S1R 16340 @ 550mah with 10C (written under the white info box.) so thats
.55amps x 10= 5.5 amps

I bet your completely confused now, where you almost had it afore...
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[Mx1252]

I bet your completely confused now, where you almost had it afore...
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Haha. Funny. But true. I did now have to look it up that new concept. More work to do ! Specifically It does another confusion layer when I see the nitecore 21700 5000mah capacity don't have a C rating but say they are rated at 8A. So that would equate to a C rating of 1.6. It's either low or I need do do
more research. I think both of those are true.

 

[ScapegoatUmi]

With such a high capacity, at just slightly larger volume compared to 18650, or even these tiny cells mentioned above, remember the 3 trade off of a battery? Capacity vs amp discharge vs cost? That 1.6 could very well be true. High capacity typically do not discharge quickly......


Edit: I poorly described the above.

High capacity typically do not have as high a C rating, HOWEVER, with higher capacity, a lower C still gives lots of current..

That 5000mah cell with a 1.6C is capable of discharging (handling a requirement of) a current of 8amps.

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[ChrisGarrett]

Haha. Funny. But true. I did now have to look it up that new concept. More work to do ! Specifically It does another confusion layer when I see the nitecore 21700 5000mah capacity don't have a C rating but say they are rated at 8A. So that would equate to a C rating of 1.6. It's either low or I need do do
more research. I think both of those are true.

'C' rating for li-ions/batteries is more commonly referring to capacity and or charging current, where 5000mAh would be expressed as 5C. If you see a recommended charging current of 2.5C, that would mean 2.5A.

For discharge current, we generally just use amps/current expressed as 'A, or mA.'

Chris

 

[HKJ]

'C' rating for li-ions/batteries is more commonly referring to capacity and or charging current, where 5000mAh would be expressed as 5C. If you see a recommended charging current of 2.5C, that would mean 2.5A.

For discharge current, we generally just use amps/current expressed as 'A, or mA.'

No, the C referrers to the capacity of the battery, i.e. a current of 2.5C is 2.5*5000->12.5A for a 5000mAh battery, for a 3000mAh battery the same 2.5 would be a lower current: 2.5*3000->7.5A

 

[ScapegoatUmi]

No, the C referrers to the capacity of the battery, i.e. a current of 2.5C is 2.5*5000->12.5A for a 5000mAh battery, for a 3000mAh battery the same 2.5 would be a lower current: 2.5*3000->7.5A

Thank you

By the way, the 1.6C on a
5000 mah, (5amp hour) cell is 8amps. That is a lot of current!!


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