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Hope you don’t mind but I’m going to leave a piece from my blog on ohm’s law here

Watts- a unit of measurement in electronics to indicate applied power

Volts- a unit of measurement in electronics to indicate pressure applied to current to create power

Resistance- a unit of measurement in electronics to indicate resistance applied to the current to create pressure

amperage- a unit of measurement in electronics to indicate current flow

Ohms Law


I have written about ohms law more times than I care to say, however, I am going to try my best to simplify this as much as possible.

Think of a circuit as a hose. The water flowing through the hose is the electricity or current(amps). The pressure pushing the water is the voltage. Now pinch the hose. Pinching the hose is adding Resistance. The pressure building up is voltage and the current flow has now decreased because you applied resistance.

Now if you take that Voltage or pressure and Multiply it by the Current or Amperage you are given your power or wattage measurement.

The problem comes in when you have a 20a battery but are trying to force it to give you more current than it has to offer.

All 4 parts that make a circuit happen are happening in conjunction with each other and as an added note to the beauty of it, whatever energy is put in must be equal to the energy coming out. What this means is that all you need are two bits of information to determine the others.

Ohms law is basically the relation of those bits of information. If you multiply the resistance applied by the current you are then given your voltage or force applied.

For ease of use the forumulas are

V=IR and P=VI
V= voltage
I=current (amps)
P=power (watts)
R= resistance(ohms)

Why does ohms law matter? Batteries!

Why do you see some of us harp on ohms law? Because batteries. A battery is a limited space to hold energy. This means that we have to work within our limits. You don’t want to overdraw on your batteries. If you do bad things can happen, such as venting a battery or causing a battery to explode.

Make sure you use a battery with a 20 amp limit, meaning that If we assume the voltage after the spike from charging to be between 3.7 and 3.8 volts then the most we want to push the battery is about 75watts with a 0.18 ohm load at best. I try and preach that we stick with 20A batteries from known manufacturers. This essentially narrows down to: Samsung 25r, Sony vtc4 AND vtc5, and LGhe4.

What if my mod takes two batteries? In the even that your mod uses multiple batteries, use batteries purchased together from the same manufacturer and keep them together. We call that “married pairs” when one stops working replace them both.


better ohms law explanation
Ohm’s Law – The basics – Ohms Law Formulas Explained to save you time

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.
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.

The following are a list of batteries and their specs as tested by ‘mooch’- a fellow vapor and accepted as a battery expert.


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