Hi all. Question regarding Ohms, Voltage, and Watts. I understand that you need batteries that have enough amps to drive your device if your sub-ohm'ing, so if you have a coil that is rated at .15 ohms, your batteries should be rated at least at 28 amps. My question is what if I am vaping a sub-ohm coil at .15 ohms, but only have 20 amp batteries but I'm only vaping at 60 watts. Using the VapeCalc, I see that that would only require 20 amps draw. Am I on the right track or am I way in left field? Is this safe? I do plan on getting 30 amp batteries (Sony VTC4), but I'm running LG HG2 20 amps right now and was just wondering if I kept the watts down would it be safe to vape (at least until I get my new Sony batteries)?
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Question on Ohms, Voltage, and Watts
- Thread starter Sacto95827
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With a regulated single battery mod at 60W (or with two battery mod at 120W) you are pushing between 16-21A +- depending on how full your battery(s) is.
This has nothing to do with the resistance of the coil.
This has nothing to do with the resistance of the coil.
Thanks Gakudzu. Although I think I have an updated chart that Mooch has posted (I believe it's Mooch) that shows upper limits as well. So true the continuous amperage for the VTC4 is 23A, it has a max of 30A
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Thanks! Hadn't seen that chart yet.
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Everything is explained in detail in this thread
http://vapingunderground.com/threads/anthony-vapes-presents-vaping-safety-101.300140/
So my concern is not pushing the battery past its amp limit. I read the way to calculate this is to take max voltage of battery (in this case 4.2v) and divide it by the resistance or ohms of your coil (my case 0.15), giving me 28A, 8 more amps than my battery at 20A (basically Ohms Law). So I'm confused when say it has nothing to do with your coil.
Ohm's law refers to calculating the amp load with an unregulated device.
With a regulated device the calculations are different and do not include the coil resistance, which is irrelevant.
Since the coils is not directly connected to the battery and passes through a regulator, the amp load at the chip and at the battery are different.
With a regulated device the calculations are different and do not include the coil resistance, which is irrelevant.
Since the coils is not directly connected to the battery and passes through a regulator, the amp load at the chip and at the battery are different.
Ohms are directly related to voltage (both are quantities dealing with resistance and overcoming it). Watts is voltage*amps. Ohms law defines the relationship between resistance (ohm), voltage (volt), and draw (amp). The voltage overcomes the resistance, the amps are what are being transported and make heat.
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Look at ohm's law
Here is a more in depth look at ohms law
Ohm's Law - https://learn.sparkfun.com/tutorials/voltage-current-resistance-and-ohms-law
When choosing a battery for your mod it is important to make sure that the battery can handle the current that you are pulling from the battery. Also ensure you know the limitations of your mod per the manufacturer.
Using ohms law you can easily determine the current draw. Please see the threads authored by baditude, here in the battery section; or, myself in the beginner area.
ohms law-V = I x R Or I = V/R when I=current(amps), V=voltage, R=resistance(ohms)
So, if I need the current for a battery- I am assuming the battery at mean voltage therefore it is at 3.7v. and I am firing a 0.5 ohm resistance. Those are my two constants for the same of our math.
I would use the following as my equation:
I = 3.7v/0.5ohms
in this case I am only pulling 7.4A and 27.4 w; therefore, I want s battery that is capable of providing 7.4A safely.
admittingly, as the chart shows, most batteries can handle this. problems ome into play when people fire to far low.
NOW, lets try this with a 0.2 ohm load (coil), the voltage is the same here.
I=3.7v/0.5ohms
in this case we have 18.5amps and 68.45 w. Therefore, it is easily illustrated that the field of suitable batteries, has greatly been reduced to cells that can handle a continuous current of 20A.
But- To directly answer your question, I would not advise anyone to go below a 0.2ohm build with those batteries.
Sent from my XT1650 using Tapatalk
Here is a more in depth look at ohms law
Ohm's Law - https://learn.sparkfun.com/tutorials/voltage-current-resistance-and-ohms-law
When choosing a battery for your mod it is important to make sure that the battery can handle the current that you are pulling from the battery. Also ensure you know the limitations of your mod per the manufacturer.
Using ohms law you can easily determine the current draw. Please see the threads authored by baditude, here in the battery section; or, myself in the beginner area.
ohms law-V = I x R Or I = V/R when I=current(amps), V=voltage, R=resistance(ohms)
So, if I need the current for a battery- I am assuming the battery at mean voltage therefore it is at 3.7v. and I am firing a 0.5 ohm resistance. Those are my two constants for the same of our math.
I would use the following as my equation:
I = 3.7v/0.5ohms
in this case I am only pulling 7.4A and 27.4 w; therefore, I want s battery that is capable of providing 7.4A safely.
admittingly, as the chart shows, most batteries can handle this. problems ome into play when people fire to far low.
NOW, lets try this with a 0.2 ohm load (coil), the voltage is the same here.
I=3.7v/0.5ohms
in this case we have 18.5amps and 68.45 w. Therefore, it is easily illustrated that the field of suitable batteries, has greatly been reduced to cells that can handle a continuous current of 20A.
But- To directly answer your question, I would not advise anyone to go below a 0.2ohm build with those batteries.
Sent from my XT1650 using Tapatalk
Last edited:
Thanks all for the feedback. I am using a regulated device, so I guess I'm okay. Call me paranoid, but I just didn't want to blow off my face with all the things I have been reading. Thanks again for peace of mind.
Protected circuits can fail (not to frighten you, brakes can fail too and most of us drive without thinking about it). Always good to make sure you're not too far out of the realm of what's sane
Understood and appreciated. I think vaping at 60w on a regulated device with the 20A batteries I have will be okay for a few days. At least until I get my new Sony batteries. Like I said, you see so much online and you just hope it doesn't happen to you! Thanks all for the comments!Protected circuits can fail (not to frighten you, brakes can fail too and most of us drive without thinking about it). Always good to make sure you're not too far out of the realm of what's sane