Voltage, resistance, etc

[Dingus]

Can someone knowledgeable write a detailed explanation about voltage, resistance, amperes, etc?

There seems to be a bit of conflicting information out there.
I often read that LR should only be used at low voltages. But sometimes I see posts that claim you need high voltage for LR. I think the first one is correct, but I'm not sure.

And how do dual coils fit in? If my understanding is correct, dc's usually have two standard resistance coils, which add up to low resistance - or is it the other way round? So, how does that relate to the voltage you use?

I have seen bits and pieces of information about all this, but since I don't know anything about electricity, it's hard to put it all together...

Thanks!

 

[cedled]

here's a table of watts produced using atties on different voltages:

http://img694.imageshack.us/img694/469/wattage.png

[source: http://www.e-cigarette-forum.com/fo...05582-getting-bit-cofuuused.html#post1589841]

 

[Katya]

Dingus, what really matters is the amount of heat (power) generated by your battery and your atty.

Wattage equals voltage squared divided by resistance. The recommened safe zone is usually around 4.5-7 Watts. So, if you put a 3.1Ω carto on a 3.7 (kr8) battery: 3.7/3.1 x 3.7 = 4.4 W. That's where you want to be, especially when you're just starting. However, a 2.0Ω carto on the same battery will produce 6.84W; that's much hotter and you're approaching a dangerous territory where the filler in your cartomizer may burn or your atty's coil may pop unexpectedly.

You have to find your own sweet spot; experiment and see what Wattage works for you. Start low and work your way up until you're satisfied. Remember also that too much Wattage (heat, power) will alter the taste of your eliquids or even burn them. Generally, tobacco flavors can take a little more heat, while fruit, dessert flavors do better at cooler temperatures.

Here's a handy dandy Ohm's Law Calculator. Don't leave home without it.

Online Conversion - Ohm's Law Calculator

Things get more complicated with dual-coil cartomizers, as you're dealing with two 3.0Ω coils but 1.5Ω resistance. I don't claim to understand how those cartos work, but here's the best explanation I've come across to date:

Quote from EvilGnome6:

Ohm's Law cannot be defied. V=IR holds true regardless of the variables.

If you have two 3 Ohm coils, you have a total resistance of 1.5 Ohms. Let's take a scenario of a 4V device facing 1.5 Ohms:

4 V = I x 1.5 Ohms
I = 4/1.5
I = 2.67 Amps

If the battery can't deliver that much current something has to give. Since it can't magically increase the resistance of the coils to keep the voltage constant, it must result in a drop in voltage.

So if the max current = 2.5 Amps, this is what would happen:

V = 2.5 A x 1.5 Ohms
V = 3.75 V

 

[Dingus]

Thanks for the detailed reply. So basically, if the battery doesn't have enough amps, it will just drop the voltage? Is that safe, or could you destroy batts that way?

 

[5cardstud]

Here is a site that explains it all pretty simple. Basic DC Electricity

 

[AttyPops]

Thanks for the detailed reply. So basically, if the battery doesn't have enough amps, it will just drop the voltage? Is that safe, or could you destroy batts that way?

True on the voltage. Over-amping stresses the battery. That's one reason we suggest using protected cells. The protection circuits will usually cut the battery off as if it is shorted. Some batteries, however, are a different safer chemistry and made for "high drain" (higher amps). AW IMRs come to mind.