Understanding resistances, LR and HV
Please note: This chart is intended for off the shelf devices only, not for coil building. Use the chart and the calculator below and double check with other sources and your own calculations before committing to any coil building and usage, this is a guide, not an absolute, and is not intended to be your single source for information. Always double check your numbers. Drawing more power than your battery can handle can cause damage or worse. Generally speaking a standard ego battery can handle up to 2 amps, do your calculations to make sure you are always under this level.
Open this single coil chart in a new window or save it for reference.
“LR” stands for low-resistance (for use on 3.7V or less batteries). “HV” stands for high-voltage.
To understand this HV and LR, it helps to be familiar with Ohms Law.
Power (measured in watts) is the intensity of the vape. 6-8 watts is the “sweet spot” for most vapers.
Current (measured in amps) is what can burn out clearomizers and batteries. Roughly speaking: around 1.5 amps is fine; 2.0+ amps is risky.
But watts and amps are not properties of clearomizers or batteries. They are derived from clearomizers resistance (measured in ohms) and battery voltage (measured, of course, in volts).
Watts = Volts X Volts / Ohms
Amps = Volts / Ohms
So we need to balance battery voltage with clearomizer resistance to get an ideal vape intensity (for me it is 6-8 watts or so on a single coil over 1.5ohms) without burning out the clearomizer or damaging the battery. If the voltage is too low and/or the cartomizer resistance is too high (relative to each other), the watts are low and you get a poor vape (little throat hit, vapor, and flavor). On the other hand, if the voltage is too high and/or the clearomizer resistance is too low, the amps are high and you can burn out the clearomizer and battery. Remember over 2 amps is risky.
Regarding Resistance and Voltage Numbers
In what follows, and throughout the vaping community, we refer to clearomizer resistance and battery voltage as a set number, e.g., 2.3 ohms and 3.7V. In fact, clearomizer resistance should be viewed as +/- 0.1 ohms, e.g., a “2.3” ohm clearomizer is more like 2.2-2.4 ohms
Actual battery voltage drops considerably from fresh off the charger to stopping. The “nominal” voltage is more of an average or midpoint. For example, a “3.7V” battery starts out at 4.2V fully charged and drops down to 3.2V before demanding to be recharged. With this, larger mah batteries are desired for not only the life of the charge but the life of the charge in the sweet spot.
Standard 510/eGo Clearomizers
A standard 2.3 ohm 510 clearomizer on a 3.4V 510 thin battery generates a safe 1.5 amps … but only 5 watts of power: not bad, but not intense enough for many vapers.
That same clearomizer on a 3.7V battery yields 6 watts and 1.7 amps: nice vaping with little risk of coil burnout.
Most “HR” (high resistance) clearomizers are 4.5 ohms resistance and above and are intended for use on 6V or Higher Mods.
NOTE: We do NOT recommend EVER stacking batteries for ANY reason, the info here is just that, info. I recommend using a mod that can boost the voltage with just a single battery.
This results in 8 watts of vaping (very nice) and 1.3 amps current (a conservative level).
Some HR clearomizer are 3.5 ohms, intended for use on 5V mods: 7 watts and 1.4 amps.
Others are 5.2 ohms, intended for 7.4V mods: 10.5 watts and 1.4 amps.
So a correct matching of these “HR” clearomizer with these 5.0, 6.0, and 7.4 voltage levels delivers a powerful yet safe vape.
LR (low resistance) clearomizers are intended to yield vape intensity (watts) on 3.4V or 3.7V similar to what the higher voltage mods deliver. But some of them generate damaging current.
The further you push the amps above 1.5, the greater the risk of burning out a coil and damaging your battery (or worse)
The typical resistance of LR clearomizers is 1.5 ohms. Vapers routinely use such 1.5 ohm LR clearomizers on 3.4V eGos (7.7 watts and 2.3 amps) all the time: excellent vape intensity … but the life span of this tye of usage is much shorter due to the intensity.
There is no physical danger in these higher amps, nothing blows up. It’s just that 1.5 ohm clearomizers die faster than standard (or high) resistance clearomizers and the batteries are stressed more.
Another consequence of the high amps created by 1.5 ohm LR clearomizers is that they should only be used on batteries of at least 450 mAh. So no dinky 510's!!
Ultra Low or sub ohm coils:
We are not covering ultra low (under 1.5) or SubOhm (under 1.0) coils these are dangerous to use if you do not know what you are doing or have the proper batteries. Subohms are not safe on standard ecig batteries.
If your set ohms is not on the chart, don't use it!
Download the full ranges of voltage and resistance Chart here for single coils which includes optimal resistances and voltage up to 6V (if your mod goes higher break out the claculator!)
This simplified chart below is just a quick simple non absolute reference, please look at the chart linked above for more detailed info.
|Battery/Voltage||Single Coil||Dual Coil|
|510, 901, 808||2.0 - 2.5 ohm||NO!|
|eGo Batteries||2.0 - 2.5 ohms.||1.5-1.7 ohms|
|3.7v (Go-go, Larger eGo, Riva)||2.0 to 3.2 ohms||1.7-2.0 ohms|
|5v (Variable Voltage)||2.5 to 3.2 ohms||2 ohms|
|6v (Variable Voltage)||3.2 ohms and up||2.5 ohms|
|7v (Variable Voltage)||4.5 to 5 ohms||3 ohms|
Dual coil clearomizers seem to be all the rage lately but there is some confusion on how they actually work.
A dual coil consists of two coils of the same resistance. They are wired in parallel so the total resistance is half the resistance of either coil.
The total resistance of the 1.5ohm dual coil is 1.5ohms, but the resistance of either coil it contains is 3ohms. Both coils are actually 3.0ohms individually, together they are not 6.0, they are 1.5ohms
A 1.5ohm carto at 3.7V would be drawing 3.7/1.5=2.47 amps. But the single coil is burning at 3.7^2 / 1.5 = 9.13 Watts, while each coil of a dual coil 1.5ohm carto is burning at (3.7^2/1.5) / 2 = 4.57 watts. You are spliting the overall power between the two coils but still using the same amount at 9.13 Watts. Always consider the entire power draw when building coils.
Although you can certainly get away with it, a 3.7v device is not ideal for a DC carto, you should use a 4.5v or better.
How it works (graphically)
Please note: The chart above is intended for off the shelf devices only, not for coil building. Use the chart above and the calculator below and double check with other sources before comitting to any coil building and usage, this is a guide, not an absolute, always double check your numbers. Drawing more power than your battery can handle can cause damage or worse. Generally speaking a standard ego battery can handle up to 2 amps, do your calculations to make sure you are always under this level.
Enter any two known values and press "Calculate" to solve for the others. For example, an eGo having a rating of 3.7 volts AC and using a carto of 2.5ohms will draw 1.48 Amps and 5.476 watts.
Voltage (E) = Current (I) * Resistance (R)
Power (watts) = Current Squared (I^2) * Resistance (R)
Power = I*E = E^2 / R