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E-Cigarette Battery Safety & Ohms Law

Battery Safety & Ohm’s Law For Electronic Cigarettes

By Nick Bessette


 There are literally millions of vapers nowadays and a lot of who are trying out the art of building their own coils and/or using a sub ohm tank. There are a few things that everyone should know before they delve into the realm of rebuilding and sub-ohming; battery safety and Ohm’s Law are on the top of that list. The following will be a step-by-step guide on the Do’s & Don’ts of the subculture of vaping.

Battery Safety

 It may seem like common sense to use the right tool for the job but for a beginner, there’s so much information available to you it might seem a bit overwhelming. Hopefully these tips will get you on the right track for being a responsible APV (Advanced Personal Vaporizer) or “mod” owner.

  • Never Fully Discharge or Overcharge Your Batteries- When charging, keep an eye on your batteries and make sure you take them off the charger when they say they are fully charged (most of the time at 4.2v.) Most modern chargers are equipped with overcharge protection but that doesn’t mean you should just leave them on until you’re ready to use them. Batteries slowly drain even when they’re not being used in a mod so if you leave them on they will continuously be cycling even though they still read 4.2v. Also make sure you take out your batteries before they hit their lowest charge rate (most of the time at 3.5v,) you should notice a significant loss of power when using a mechanical (mech) mod when the batteries are starting to drain. When this happens take it out and swap it for a fully charged cell.
  • Never Leave Your Batteries on the Charger Overnight- This can cause the battery to have a reduce life cycle and any chance to extend the life of your batteries is one you should take into consideration. Not to mention the fact that Li-ion batteries are very fragile so you should always be cautious when using them and keep an eye on the charging process. Furthermore, make sure your charger is in a safe place out of the reach of children and never on the carpet.
  • Buy the Right Battery for the Job- Buying batteries can be a pain with so many different brands to choose from. First of all, when something has the word “Fire” in the name, it’s best not to “Trust” it. If you’re using a regulated device that only goes up to 15w and is not capable of sub-ohming, you should most likely use an AW IMR protected cell battery. There are several sizes to choose from including 18350, 18450/500 and 18650 among others. Make sure you purchase the correct battery size for your device and never stack batteries. If you’re using a mech mod, you will need an unprotected high drain cell such as the Samsung 25R “Smurfs” or the Sony VTC4’s. These batteries are capable of putting out a much higher amperage than protected cells and if you are using it with a sub-ohm coil, you will be also using a higher than average amp draw from your battery.
  • Don’t Short Out Your Batteries- A short circuit is like a shortcut that electricity can take on it’s way from the positive to negative terminals. This can be caused when your positive and negative terminal touch the battery at the same time such as using a hybrid connection with a device with a shallow positive pin but a short can also be caused by a number of other factors as well. One thing to stay away from is storing batteries with other metal objects. This means don’t just throw your batteries in your pocket with your keys and loose change as it can short your battery and even explode! The telltale sign of a short is your battery and mod will get very hot. Don’t risk using a battery that you shorted out, a $15 battery is definitely not worth risking your hand over.
  • Always Check Your Battery Wrappers For Rips- This is a common problem that is all too often overlooked. I’ve seen countless customers come into my vape shop that have tears in their battery wrappers and think it’s not a big deal but they are definitely wrong. Even if it’s a minor tear you should always rewrap it because if it’s left untreated, it could get larger or possibly short your battery and cause you to get shocked. Battery rewraps are cheap and easy to do, simply peel the old wrapper off your battery, slide the new one over it (trim if necessary) and heat it using a hair dryer. Presto! You’re ready to start vaping safely once again.
  • Know the Amp Limit of Your Batteries- The following is a table that shows the amp limits for all of the most popular battery brands on the market today. It’s important to know this so you can use the right battery for the resistance of the coils you’re building.


Battery Name & mah Continuous Discharge Amps Maximum Discharge Amps C Rating Safe Ohm to run
AW 14500 600 mah 4.8 amp 6 amp 8c 0.9 ohm
AW 16340 550 mah 4.4 amps 5.5 amp 8c 1 ohm
AW 18350  700 mah 6.4 amp 7 amp 8c 0.7 ohm
AW 18490  1100 mah 8.8 amp 11 amp 8c 0.5 ohm
AW 18650 1600 mah 16 amp 24 amp 15c 0.3 ohm
AW 18650 2000 mah 7.5 amp 10 amp 5c 0.5 ohm
Efest IMR
Efest 10440 350 mah 1.4 amp 3 amp 8c 3 ohm
Efest 14500 700 mah 5.6 amp 7 amp 8c 0.8 ohm
Efest 16340 700 mah 5.6 amp 7 amp 8c 0.8 ohm
Efest 18350 800 mah 6.4 amp 8 amp 8c 0.7 ohm
Efest 18490 1100 mah 8.8 amp 11 amp 8c 0.5 ohm
Efest 18650 1600 mah 20 amp 30 amp 18.75c 0.3 ohm
Efest 18650 2000 mah 15 amp 20 amp 8c 0.4 ohm
Efest 18650 2250 mah 18 amp 20 amp 8c 0.5 ohm
Efest 26500 3000 mah 20 amp 30 amp 6.5c 0.5 ohm
Efest 26650 3000 mah 20 amp 30 amp 6.5c 0.5 ohm
EH 14500 600 mah 4.8 amp 6 amp 8c 0.9 ohm
EH 15270 400 mah 3.2 amp 4 amp 8c 1.4 ohm
EH 18350 800 mah 6.4 amp 8 amp 8c 0.7 ohm
EH 18500 1100 mah 8.8 amp 11 amp 8c 0.5 ohm
EH 18650 2000 mah 16 amp 20 amp 8c 0.4 ohm
EH 18650 NP 1600 mah 20 amp 30 amp 18.75 c 0.3 ohm
MNKE 18650 20 amp 30 amp 18.75c 0.3 ohm
MNKE 26650 20 amp 30 amp (60 amp pulse) 18.75c 0.3 ohm
Samsung ICR INR
Samsung ICR18650-22P 2200 mah 5 amp 10 amp 4.5c 0.9 ohm
Samsung ICR18650- 30A 3000 mah 2.4 amp 5.9 amp 1c 1.5 ohm
Samsung INR18650-20R 2000 mah 7.5 amp 15 amp 7c 0.6 ohm
Sony US18650v3 2150 mah 5 amp 10 amp 4.5c 0.9 ohm
Sony US18650VTC3 1600 mah 15 amp 30 amp 18.75c 0.3 ohm
Sony US18650VTC4 2100 mah 15 amp 30 amp 14c 0.3 ohm
Sony US18650VTC5 2600 mah 15 amp 30 amp 11.5c 0.3 ohm
Trustfire IMR
Trustfire 14500 700 mah 2 amp 4 amp 2c 2.2 ohm
Trustfire 16340 700 mah 2 amp 4 amp 2c 2.2 ohm
Trustfire 18350 800 mah 4 amp 6.4 amp 5c 1.1 ohm
Trustfire 18500 1300 mah 6.5 amp 8.5 amp 5c 0.7 ohm
Trustfire 18650 1500 mah 7.5 amp 10 amp 5c 0.6 ohm
NCR18650B 18650 3 amp 4 amp 1.1c 1.5 ohm
NCR18650PF 18650 5 amp 10 amp 3.4c 0.9 ohm
NCR18650PD 18650 5 amp 10 amp 3.4 c 0.9 ohm
NCR18650 18650 2.7 amps 5.5 amps .5 c 1.6 ohm


Ohm’s Law

Ohm’s Law is the relationship between three mathematical equations relating to the flow of electricity. It may be difficult for those of you who don’t have a preexisting knowledge of electricity so I’ll try to make it easy for you and relate it to a highway.

What is voltage? Voltage would be like a huge super-highway with lots of cars speeding down it. The speed at which the cars travel is determined by their own top speed and how many lanes are in the highway. The difference between the speed at which the cars are travelling and the cars maximum speed could be thought of as potential voltage.

What is current? The best analogy for current would be the fastest speed the cars can travel as determined by their own top speed (voltage.) The quantity, volume or intensity of electrical flow would best describe current, as opposed to voltage, which refers to the force or “top speed” causing the current flow.

What is resistance? Resistance is like a bottleneck where four lanes get reduced to two and the traffic is forced to slow down. The more lanes (lower resistance), the faster traffic can go and the fewer number of lanes (higher resistance) the slower it can move. The coils you build are the resistance in the case of vaping. All three of these factors play a crucial part in Ohm’s Law.

Ohm’s Law can be stated as mathematical equations, all derived from the 
same principle. 
In the following equations, 
V is voltage measured in volts (the size of the highway), I is current measured in amperes (related to the top speed (Voltage) of cars speeding down the highway) and

 R is resistance measured in ohms as related to the size of the highway:

 V = I x R  (Voltage = Current multiplied by Resistance)

R = V / I  (Resistance = Voltage divided by Current)

I = V / R  (Current = Voltage Divided by Resistance)

Knowing any two of the values of a circuit, one can determine (calculate) the third, using Ohm’s Law.

 For example, when building coils, you will have your known maximum voltage output (4.2v for most batteries) and your resistance (Ohms) so when you plug those two factors into the equation you can determine how many amps you will be drawing from your battery. This information is crucial because you don’t want to be going over the amp limits of your batteries. There are helpful tools out there to help you with this including websites and even apps that you can plug in the known factors to determine the amps your drawing from your batteries. Always use an Ohm reader or multi-meter when rebuilding so that you know the resistance of your coils and have the numbers you can plug into these formulas.



This wheel is divided into three sections:

Volts V (on top of the dividing line)
Amps (amperes) I (lower left below the dividing line)
Resistance R (lower right below the dividing line)
X represents the (multiply by sign)
You might want to memorize this wheel



 At this point you should have a solid knowledge base of the safety aspect to vaping and hopefully have gained some knowledge on how batteries work as well. The information that I really want you all to take away from this is how important safety is when it comes to rebuilding your own coils. I see far too often people using unsafe batteries or making coils that would make an electrician cringe. The more accidents we have as vapers, the more the media will show bad press and push for more regulations. Vape safe everyone and as always, vape on!