Post by Balders on Mar 4, 2017 16:25:17 GMT
Ohm's Law is a scientific formula used to describe the relationship between power (Watts=W), resistance (Ohms=O), energy (Volts=V) and current (Amps=A). All these things are important when vaping, as they correlate to the output of your device and safety of your cells.
So how does Ohm's Law work? And why does it matter?
It matters for people who are building your own coils, because it helps you know what is safe to vape or not. If you use a super sub-ohm build, it can draw too much power from your cells, and if you go over the amp rating of your cells, it can damage them and also damage your device or potentially your face. And we don't want you to damage your face.
DISCLAIMER: I need to say this up front, Ohm's Law does not apply perfectly in the real world, since it does not account for things like your mod's internal resistance, battery voltage sag, and tons of other factors. So use it as a general guide, but not as a perfect rule. If you use Ohm's Law and the math says it's safe to vape at .0003 ohms, DON'T. As a general rule, I consider it unsafe to vape with anything lower than .3 ohms, even if the theoretical math equation says differently. Better to be safe than sorry.
The Formula
There are a lot of variations of the formula used in Ohm's Law, so here are a few formulas that I find helpful:
A=V/O - this one is what I use to find the amps that are being drawn when I use a build with a certain resistance.
O=V/A - this is what I use when I need to know the lowest resistance I can safely use on a given cell.
O=W/A2 - this is what I use to find the lowest resistance I can use safely at a given wattage.
How to Use It
So how does this work in real life?
Example 1: Let's say I want to know if it's safe to vape at .09 ohms on a Samsung 25R cell. Since all 18650 cells have a 4.2V maximum charge, I can plug 4.2 into any of the formulas that have a V in them. I need to solve the formula for A, so I can see if it's within the cell's rating limits. I'll use the first formula:
A=V/O
A=4.2/.09
A=46.67 amps
I know for a fact that the Samsung 25R is rated up to about 20 amps, so the .09 ohm build will be drawing far too much power and therefore not be safe to use.
Example 2: So what resistance is safe to use? Since we know that the amps need to be 20 or less, we can plug 20 in for A and 4.2 in for V using the second formula:
O=V/A
O=4.2/20
O=.21 ohms
So how does Ohm's Law work? And why does it matter?
It matters for people who are building your own coils, because it helps you know what is safe to vape or not. If you use a super sub-ohm build, it can draw too much power from your cells, and if you go over the amp rating of your cells, it can damage them and also damage your device or potentially your face. And we don't want you to damage your face.
DISCLAIMER: I need to say this up front, Ohm's Law does not apply perfectly in the real world, since it does not account for things like your mod's internal resistance, battery voltage sag, and tons of other factors. So use it as a general guide, but not as a perfect rule. If you use Ohm's Law and the math says it's safe to vape at .0003 ohms, DON'T. As a general rule, I consider it unsafe to vape with anything lower than .3 ohms, even if the theoretical math equation says differently. Better to be safe than sorry.
The Formula
There are a lot of variations of the formula used in Ohm's Law, so here are a few formulas that I find helpful:
A=V/O - this one is what I use to find the amps that are being drawn when I use a build with a certain resistance.
O=V/A - this is what I use when I need to know the lowest resistance I can safely use on a given cell.
O=W/A2 - this is what I use to find the lowest resistance I can use safely at a given wattage.
How to Use It
So how does this work in real life?
Example 1: Let's say I want to know if it's safe to vape at .09 ohms on a Samsung 25R cell. Since all 18650 cells have a 4.2V maximum charge, I can plug 4.2 into any of the formulas that have a V in them. I need to solve the formula for A, so I can see if it's within the cell's rating limits. I'll use the first formula:
A=V/O
A=4.2/.09
A=46.67 amps
I know for a fact that the Samsung 25R is rated up to about 20 amps, so the .09 ohm build will be drawing far too much power and therefore not be safe to use.
Example 2: So what resistance is safe to use? Since we know that the amps need to be 20 or less, we can plug 20 in for A and 4.2 in for V using the second formula:
O=V/A
O=4.2/20
O=.21 ohms
