It's really weird, but I can actually get my vv3s to fire all the way down to .8 -- anything lower and it won't fire at all, but the fact that it fires lower than 1.3, that amazed me -- my sigelei and vamo won't, and my kicks won't fire below 1.0.
Andria
It's a number set by the manufacturer that varies.
If you look it up they probably say it's around 1.2Ω or something similar for safety reasons.
There's something specific I want to mention that's related to that aspect but normally saved for cloud chasers, however, since a lot of us rebuild and things can go wrong easily I thought it was worth it as it pertains to safety.
The concept is called "Pulse Range" and basically it means to pull more amperage out of a battery for a short burst than it can safely discharge for a continuous amount of time (a 5 second draw from an e-cigarette for example).
If you look at the batteries we are using (originally intended for low current devices like flashlights) there are 2 basic types, high drain and low drain. The high drain style, like the 30 amp Sony VTC5's and similar have a continuous amp draw rating of 30 amps; most of the low drain batteries have an amp draw around 10 amps and below.
What happens when you enter pulse range is the battery rapidly transfers energy, faster than the chemistry (be it ICR or IMR) is designed for. The result is that it heats up very rapidly, some reports say a couple hundred degrees a second! That is the reason that your switch gets hot when there is a short, well, that and that the switch is *normally* the only moving part of the circuit AND therefore the first part to fail/break.
Many cloud chasers do this intentionally with a very low ohm build on a single battery to produce very high amounts of vapor; if they are careful, the situation can be done safely (most competitions actually limit the build being used to stay within safe operating limits of the batteries, make entrants prove their builds and the batteries they are using) and repeatably... even if the batteries get permanently damaged.
With newer regulated devices this practice has become obsolete as the power level can be raised (the limited power of single battery mechanical mods was the main reason for doing this in the first place) eliminating the need to push batteries to the point of failure.
Speaking of mechanical mods, the new style "parallel and series" box mods that are designed to be fully mechanical and have no "over-current protection" still allow for the exact same condition to happen. Many manufacturers are now building in current protection in the form of self-resetting fuses that limit the current draw allowed to reach the atomizer. (See findmyvapes.com for build kits if interested.) Just a quick note, parallel box mods allow for longer battery life and series for higher power... basically.
The point I wanted to make is this, if you are going to rebuild, PLEASE learn to do it safely. It is not that complicated to do, even for an ego battery but doing it wrong will be a very bad day for all of us. There are many online calculators that will give you the amp draw for a stock set of resistances but this only tells you half of the story - you also need to know the amp draw your battery is rated for, just a simple Google search away. If you can't find the rating, stay to the resistance of your most used factory made coils, they have been safe for a long time and there is a reason why they are made to that large of a resistance.
Also, I hate to ever suggest that anyone spend money, but... most batteries we use have somewhere around 1000 charges before they start to lose performance. Meaning they will start to not stay charged as long and MAY not be quite as safe
if pushed to their limit.
So yes, Andria... long story short, but if you are just starting, staying around 1.5Ω or above until you are comfortable with the rebuild process and can hit the mark consistently is a very good idea, with any device. Your battery MAY be able to go lower than that, but it only take a fraction of a second for it to go bad in a big way.
Most importantly, know your equipment and practice. Get a resistance meter or multimeter and know how to use it, know your batteries and the devices they are in and what they can handle safely.
Rules are made to be broken, but only once you know what those rules are... and the consequences for breaking them. How serious is it if done wrong? Just Google "Vape Blast" and check out the aftermath of the explosion.
Finally, is rebuilding safe? Absolutely. Can it be done with just a few minutes of training (depending on the device being built)? Yes. When you start trying for the first time, ask a few simple questions and make sure you are safe, it's hard to type congrats on not smoking posts without fingers lol!
Basic rule of thumb, for 28ga kanthal wire, a 1.5Ω coil means using 3 1/4 inches of wire... on any mandrel or screwdriver!
If ANYONE wants more info, please let me know, I'll be happy to get you the info needed to rebuild safely and enjoyably.
Thanks.
/rant