Alkuperäinen postaaja
Joku
An 18650 is a rechargable li-ion cell that's 18mm in diameter, 65mm in length, and cylindrical (hence the number in its name -- the 0 indicates a cylindrical shape). All 18650 cells, and other cells specified by number like that, are by definition rechargable lithium-cobalt cells with a nominal voltage of 3.7v; that is, there's no such thing as a non-rechargable 18650. Lithium-ion is generally used synonymously with lithium-cobalt.
No, it does not mean that by definition -- that designation is only part of the proper IEC61960 designation which does specify chemistry, and is used for other chemistries; it also seem closely related to (and is certainly capable of being confused with) the designations defined in IEC 60086 for primary cells (e.g. CR17345). At best, you could argue that it specifies chemistry by convention, but while I'm not aware of any primary cells sold by 5-digit designation without a prefix, other Li-ion chemistries most definitely are, so not even close.
The full IEC61960 designation (as near as I can tell -- unfortunately, I don't have access to the standards) looks like "ICR18650":
I: Lithium form
- I: Lithium ion
- L: Metallic lithium
C: Cathode material
- C: Cobalt-based
- F: Iron-based
- M: Manganese-based
- N: Nickel-based
- V: Vanadium-based
R: Shape (note that this is already specified here, so I'm rather sure the 5th digit does not designate shape)
- R: Round (cylindrical)
- P: Prismatic (rectangular)
18650: Size code, interpretation depends on shape:
- Round:
18: 2 digits, diameter in mm
65: 2 digits, length in mm if <100mm, or length/10 if over 100mm (e.g. M cell: IFR42120)
0: Not 100% sure -- it's obviously not a shape indicator, since that's already specified, and there's no corresponding lone digit for prismatic cells (see below). It is usually 0, but not always, e.g. I have some RCR2 labeled ICR15266, and have seen references to ICR17335 and ICR17345. I suspect it's 0.1mm digit, but lengths are usually rounded to nearest 1mm?
- Prismatic:
17: 2 digits, thickness in mm if 1mm, or 't' followed by one digit in tenths of mm.
60: 2 digits, width in mm.
65: 2 digits, height in mm.
While using the size specification only is common and useful, it does not indicate anything except the size (and frequently misses that substantially, as sometimes protection boards, button tops, etc. are included and sometimes not). Specifications such as RCR123 are no more specific, as they are also applied to LiCo cells (3.7V, way too hot for CR123-only applications), LiFePO4 cells (3.2V, lower capacity, still hotter than CR123, but may work in some applications, and sometimes marketed as "3V RCR123"), or LiCo with 3V regulating circuit (low capacity, generates heat, doesn't work well for all applications -- also marketed as "3V RCR123").
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