EDIT: I have a new comprehensive chart for optimal vaping for Voltage and Ohms, check it out here: Or click here to get it full size I posted this on my website, most of the information was gleaned from other sites and ECF. I hope this helps some, I've been getting ton of questions about resistance lately. If anyone sees any glaring errors, feel free to correct me. I am not an expert. This is also on my website with a calculator here: Undestanding resistances, LR and HV Undestanding resistances, LR and HV “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 Chart here This simplified chart below is just a quick reference, please look at the chart linked above for more detailed info.