The general answer to volts and ohms and batteries, relevant to single coil atomizers and cartomizers
For typical voltage batteries which are around 3.4 to 3.7 ohms:
Slim batteries - the general rule is nothing LR on these. Use 2.5 to 3 ohms only. If TW ships an LR atty with slim 510 I have no idea why. But they also gave me an Ego cable with my 510 (which damaged 5 510 batteries before I figured that out) so who knows.
Fat battery models and mods 450mah+ - these can use standard resistance or LR stuff. However mass produced fat battery model (Ego, Riva 510, etc) may be damaged or killed by extreme LR by which I mean stuff under 1.7ohm and some people won't go below 2 ohms on these.
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For mods - Mods come in different voltages and some are variable voltage. Typical voltages are 3.7, 5, 6, 7 and variable. Mods use removable industrial protected Lithium Ion or AW IMR batteries which look similar to flashlight batteries. With these you choose your ohms relative to the voltage. As a simplistic explanation, for single
coils, you will get this effect - for ohms of each of these amounts less than the voltage you get the following effect (ie 1 less than voltage, 1.5 less than voltage etc)
.5 barely warm
1 warmer
1.5 hotter
2 even hotter
2.2 even hotter and beyond this you may damage something
So a 3 ohm atty is barely warm at 3.7v, very hot at 5v, and will probably pop and die at 7v
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dual coils - these are different. A 1.5 ohm dual coil is 2 3 ohm coils. The amount of current 1.5 ohms draws may damage some fat batteries and is best used on mods. But it's really just 2 standard resistance coils, so rather than being hot it's a double amount of somewhat warm vapor.