what does the number 18650,18350,etc mean?

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Super Member
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Jul 3, 2013
Cary, NC, USA
I believe the numerical designations are somewhere around here in a sticky, but I CBA to go dig it up. 18 is the diameter in..I believe millimeters, and 350, 500, 650, etc is the length, insert a decimal point before the last number, so 35.0mm, 50.0mm, 65.0mm, etc. As far as sub-ohm coils and battery tolerances, look at the specs for your battery and check the continuous/peak discharge rates, then just calculate amperage with ohms/volts (or watts if using a VW device), as long as it's lower than your maximum drain rating with about a 10-15% or better overhead, you should be fine. Peak is more important than constant in this case, but you don't want to use something with a horribly low constant/continuous drain figure as it could be improperly rated or of poor quality where they fudged results to get a high peak drain value.

Cactus Breath

Ultra Member
ECF Veteran
Jul 6, 2013
The battery numbers are a measurement. An 18350 is 18mm in diameter and 35mm long; an 18650 is 18mm in diameter and 65mm long. The '0' at the end just means it's a round (cylindrical, actually) battery.

As far as IMR, read this thread: http://www.e-cigarette-forum.com/forum/apv-discussion/420323-imr-batteries-what-exactly-does-imr-mean.html - it explains it in more detail than you probably want to know.

I'll let the more experienced users comment on building sub-ohm coils and such - but I'll just offer my .02 that if you don't know what an amp is, you probably need a lot more education and background before you start digging that deep into things.


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Jun 26, 2013
Caldicote tunnel
CraigHB said:
18350 : 18mm x 35.0mm.
18650 : 18mm x 65.0mm.
14500 : 14mm x 50.0 mm which happens to be the same size as an AA battery.

IMR is a product code. "I" stands for Lithium-Ion, "M" stands for the Manganese based chemistry, and "R" stands for rechargeable.

ICR is again a product code. Same as before except "C" stands for the Cobalt based chemistry.

Only the round cells commonly use these designators. There are flat cells or prismatic cells that use a Li-Ion chemsitry, but it's usually polymer based (plastic). I've never even seen the code designator for that. Everybody just calls them LiPo cells.

High drain means that the cell can handle high output currents. ICR cells are usually limited to 2 times the charge capacity in output drain. So, for example, a 750mAh 14500 ICR cell would be limited to two times 750mA or 1.5A. This is why this type of cell must be protected. It has the lowest drain capability and the highest volatility or flammability in composition.

IMR cells typically have an 8C drain limit which is 8 times the charge capacity. A IMR 14500 with 600mAh can handle 4.8A. This chemistry is less volatile than the Cobalt chemistry and has much higher drain limits so they are typically not protected internally. Though, they should have some kind of external protection because they can burn too, just not as easily.

LiPo and prsimatic cells can range in drain limit anywhere form 1/2C to 60C. They are slightly less volatile than ICR and a little more than IMR. They are typically not protected internally and should have external protection electronics. These are the type of cells you find in digital cameras and cell phones.

Generally speaking, you use an IMR cell when the device specifically calls for one. IMR cells are required for boosters (single cell VV or VW) because boosters require higher drain. With a booster, you're going from lower voltage to higher voltage. That means you're going from higher current to lower current.

IMR cells may also be required for unregulated mods if the cell is small. For example, you are limited to 1.5A with an ICR 14500. If you want to use an LR atty with a cell that size, you need an IMR cell.

In the end, the size of your cell boils down to what you want in run time versus size. That's always the big trade-off. If you want a smaller device with a smaller cell, you'll have less run time. If you want more run time, you'll have to tolerate a larger device with a larger cell.
Also using batteries that are tested to have claimed discharge rate to the draw requirement is important. :2c:


Full Member
Jun 10, 2013
basically its the size of the battery....18350 - 18650(small to large) that's the simplest way i can explain it....if you're wondering how they can hold a charge,ofcourse the bigger the battery, the more it can hold a charge....as simple as that...but you still need to read about batteries (general battery information, safety, charging and etc.)

and if you're fairly new to vaping, i suggest don't jump into rba's...read and read and read,watch videos( a lot ) first...

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