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Regulated mods, the sub-ohm myth?

by on October 15, 2014
 

Ok, So regulated mods are taking over with the proliferation of cheap 50 watt IPV’s and Sigelei’s.  100 watt mods are just around the corner, at similarly low price points, we’ve reached a level of insanity rivaling Detroit in the mid 1960’s with its muscle car wars.  Now, I know it’s been written before, and I’m going to repeat it as well as add to the conversation on this topic.  Regulated mods are the new sub-ohm, there I’ve said it, but what does it mean? The latest crop of regulated mods allows for higher Ω coils, giving more surface area being pushed power at the rate of your choosing.  Compared to a Mech, the load is drawn from the battery, and you wind up with dual or quad coils often with very large gauge wire to have any surface area, or exotic materials with lower resistances allowing for larger coils.

People love posting their latest builds, and they quite often seem to be showing off a sub-ohm coil as low as their mod can operate at. For the love of god, why? The trick thing about these new mods, are how they can power larger coils of higher resistance extremely well.  You need to use a site like the Steam engine and find your mods sweet-spot.  Taking the IPV2 as an example, 1Ω – 1.4Ω coils are where it’s at!  People need to learn to more effectively utilize the equipment they are operating.  People say 50 watts is 50 watts, and sure, but if you have 2, 3 or 4 times the surface area, 50 watts can hit more like 100 watts on a mech mod at subohms. However there are exceptions to the rule, and not all regulated mods want high ohm coils as we will find out.

Another point of discussion I’ve seen lacking though, is in terms of battery life.  I have seen several people claim they get better battery life out of their regulated mods, and in this article I plan to tackle that statement head on.

There are 2 main types of regulated mods on the market:

-Bucking AKA Step-down: A type that takes a higher voltage from the battery, stepping it down before outputting a lower voltage to the atty. Anytime you step voltage down, your available amperage increases inversely and proportionately.

-Boosting AKA Step-up: A type that takes a lower voltage, stepping it up before outputting a higher voltage to the atty. Anytime you step voltage up, your available amperage decreases inversely and proportionately.

[Note: There are also hybrids out now, which do buck-boost- A combination of the above to reach higher and or lower output voltages. – 22, Oct. 2014]

Now I am sure you are asking “Ok Kevin, how the hell does that affect me?” I will attempt to explain.


For the sake of this article, I’m going to use my regulated mods as a reference.  I have both an IPV2 and a Supermax, with the IPV2 boosting and the Supermax bucking voltage respectively. I have seen it noted that the IPV2 operates at 93% efficiency, and for the sake of this article, we will assume the Supermax operates in that same range.

On my IPV2, it runs on a single 18650, in my case a Sony VTC5, 2600mah cell with an amp limit of 30 and a nominal voltage of 3.7 volts.  If I am powering a 0.4Ω load, and pushing 50 watts the IPV2 runs at 4.41 Volts to the coils.  Math allows us to do wonderful things, and figure out many behind the scenes details of what is happening here. Also take note, the Power wheel to the right does not give us the formula for finding input vs output voltage or amperage, but it is a simple straight conversion as noted in step 3 for each example below.

  1. I = V/R:  I (Amps) is solved from dividing power by resistance, 4.41/0.4 = 11.02 amps at the coils.
  2. Calculating for efficiency: Amps divided by 93% or:  11.02/0.93 = 11.84 amps total
  3. Calculate amps drawn on battery: (Output voltage / Battery Voltage) * Output amperage = Amp load on battery: (4.41/3.7) * 11.84 = 14.11 amps drawn from the battery.

On my Supermax, it has a 2 cell Lipo battery pack, with a nominal voltage of 7.4 volts.  If I am powering that same 0.4Ω load, and pushing 50 watts the Supermax runs at 4.15 volts, again math will let me work out my amperage output to the coils, as well as the amperage drawn from my battery.

  1. I = V/R:  I (Amps) is gained from dividing power by resistance, 4.15/0.4 = 10.375 amps at the coils.
  2. Calculate efficiency: 10.375/0.93 = 11.15 amps total
  3. Calculate amps drawn on battery:  (Output voltage / Battery voltage) * output amperage = Amp load on Battery:  (4.15/7.4) * 11.15 = 6.25 amps drawn from the battery.

From the above examples you can see stepping down, or bucking your voltage source has the benefit of decreasing the amount of amps drawn from it, thus increasing battery life and happiness. Bucking voltage can be effective for sub-ohming, and in some cases such as my Supermax, sub-ohm coils are required to run higher wattage settings.  Comparatively a regulated mod boosting its voltage also boosts the amperage drawn from its power source directly inverse to the amount it steps up.

So while people claim they get better battery life on their IPV2’s while sub-ohming it is impossible. You are loosing 7% efficiency at a minimum, and you simply cannot pull energy out of thin air.  Battery life has to decrease, there is no way around it.  Then take into account they are actually increasing the amp load on their batteries, and the higher the amp load, the shorter the life.

So proving to be the exception to the rule, the Supermax steps down its voltage, and is capable of sub-ohming very effectively and efficiently.  The IPV2 example above is exactly what you do not want to run on it. It is build ideally to run coils between 1 and 1.4Ω.  To back that up, here’s the math: I have a 1.3Ω coil in my KFL+, and if I turn it up to 50 watts it runs at 5.8 volts. (No, I don’t actually run it here, it lives at 25 watts happily)

  1. I = V/R:   8.3/1.3=6.38 amps at the coils
  2. Calculate efficiency:  6.38/0.93 = 6.86 amps total
  3. Calculate amps drawn on battery:   (8.3/3.7) * 6.86 = 15.39 amps drawn from the battery.

A comparable mech build for 50 watts, would be a 0.274Ω coil at 3.7 volts nominally:

  1. I = V/R:  3.7/0.274 = 13.5 amps
  2. no efficiency calculation possible
  3. amps drawn on battery are same as above, 13.5 amps.

So you can see, saying 50 watts is 50 watts is not quiet so simple.  Surface area, efficiency losses, battery life, and many other things come in to play. On a regulated mod, 50 watts pushed to a 1.3 ohm load uses more amps then 50 watts pulled by a 0.274Ω load on a mech. What does this all mean to you though?  Vape what you like, don’t be a sheep.. learn Ohms law and keep it safe.

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