Understanding resistances, LR and HV

First, open this 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 cartomizers. Roughly speaking: around 1.5 amps is fine; 2.0+ amps is risky.

But watts and amps are not properties of cartomizers or batteries. They are derived from cartomizer resistance (measured in ohms) and battery voltage (measured, of course, in volts). 

The formulas:

Watts = Volts X Volts / Ohms
Amps = Volts / Ohms

So we need to balance battery voltage with cartomizer resistance to get an ideal vape intensity (6-8 watts or so) without burning out the cartomizer. 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 cartomizer resistance is too low, the amps are high and you can burn out the cartomizer.

Regarding Resistance and Voltage Numbers

In what follows, and throughout the vaping community, we refer to cartomizer resistance and battery voltage as a set number, e.g., 2.3 ohms and 3.7V. In fact, cartomizer resistance should be viewed as +/- 0.1 ohms, e.g., a “2.3” ohm cartomizer 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 cartomizers

A standard 2.3 ohm 510 cartomizer 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 cartomizer on a 3.7V battery like the eGo and Go-go yields 6 watts and 1.7 amps: nice vaping with little risk of cartomizer burnout. The go-go has been perfectly matched with it's proprietary cartomizer and it one of the reasons the Go-go is highly praised, but yet relatively unknown.

HV cartomizers

Most “HV” cartomizers are 4.5 ohms resistance and are intended for use on 6V mods (using two 3.0V batteries or a booster). 
NOTE: We do NOT recommend EVER stacking batteries for ANY reason, the info here is just that, info.

This results in 8 watts of vaping (very nice) and 1.3 amps current (a conservative level).

Some HV cartomizers 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 (again using two 3.7V batteries): 10.5 watts and 1.4 amps.

So a correct matching of these “HV” cartomizers with these 5.0, 6.0, and 7.4 voltage levels delivers a powerful yet safe vape.

LR cartomizers

LR cartomizers 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 an cartomizer.

The typical resistance of LR cartomizers is 1.5 ohms. Vapers routinely use such 1.5 ohm LR cartomizers 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 such high amps, nothing blows up. It’s just that 1.5 ohm cartomizers die faster than standard (or high) resistance cartomizers.

Another consequence of the high amps created by 1.5 ohm LR cartomizers is that they should only be used on batteries of at least 450 mAh. So no dinky 510's!!

Those various resistances on 5V, 6V, and 7.4V will generate the following watts (i.e., intensity of the vape) and amps (the current that damages cartomizers):


 Download the full ranges of voltage and resistance Chart here which includes optimal resistances and voltage up to 6V

This simplified chart below is just a quick 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


DC Cartomizers
Dual coil cartomizers seem to be all the rage lately but there is some confusion on how they actually work.

A dual coil carto consists of two coils of the same resistance. They are wired in parallel so the total resistance is half the resistance of either coil. 
For example:
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 power between the two coils.
Although you can certainly get away with it, a 3.7v device is not ideal for a DC cartoi, you should use a 4.5v or better.



Enter any two known values and press "Calculate" to solve for the others. For example, an eGo havng a rating of 3.7 volts AC and using a carto of 2.5ohms will draw 1.48 Amps and 5.476 watts.

Enter 100 in the Watts field and 120 in the Voltage field and press Calculate to find the resistance and current. Fields should be reset to 0 before each new calculation.

Voltage (E) = Current (I) * Resistance (R) 
Power (watts) = Current Squared (I^2) * Resistance (R) 
Power = I*E = E^2 / R

Volts (E)
Amps (I)
Ohms (R)
Power (Watts)