Mech Mod Battery Safety

Without any built-in safety features, vaping unregulated mods offers great power, but with serious consequences - so you don't have time to skip safety class

Here are the basics so you can vape safely.

Do Vapes Explode?
The only time a vape will explode is when a hobbyist has pushed the limits of the kit or set up something incorrectly, leading to a phenomenon known as "thermal runaway" (*explained next).

What is thermal runaway, and how do I prevent it? Ohms Law
Thermal runaway in a battery is where the amount of charge being used creates excess heat, which speeds up the exothermic reaction, which in turn increases the amount of charge again -> creating an exponential increase (runaway) until an explosion occurs.

There are 3 different things to do to prevent thermal runaway. 

First, ensure the vape coil resistance is high enough. Handmade coils that are under 0.2 Ohm can be a big problem. To understand it properly, you need to know the concept of "ohm's law":

I = V ÷ R

(Current, measured in amps) = (Power of Battery, measured in Volts) ÷ R (Resistance of coil, measured in Ohms).

Batteries have a maximum safe Current that they can handle, eg 20 Amps.

To vape safely, the equation above should never result in a Current value more than your battery can safely handle.

For example, if you have a 3.7 volt battery, that has a current limit of 20 amps, and a coil resistance of 0.3 Ohms, then then it would be safe:
3.7v (V) ÷0.3ohm (R) = 12.3a (I) -> and this A value is lower than the 20amp limit on the battery, so it's safe to vape.

In contrast, if the voltage was doubled then the equation wouldn't work:
7.4v ÷ 0.3ohm = 24.6amps -> OVER the A value of the battery, and therefore DANGEROUS.

You would need a coil strength of 0.4 ohms to bring the A value down to 18.5 (below the battery limit, and therefore safe).

Another way of looking at this, is that V ÷ I = Minimum Coil Resistance Required.

More Than One Battery? The Type of Circuit Is Important
When you have more than one battery, you need to understand the type of circuit before you calculate.

There are two types of circuits in mech mods:


Here are the ways to modify the equation if you have these types of circuits:

When batteries are "in series", it means that you have to add up their total voltage units to add to the ohms law equation.

So if you have 2 x 3.7V 20A batteries in series, then the total voltage to use in the equation and calculate safety is 7.4V (and the A rating stays the same).

An example: 7.4V ÷ 0.4ohms = 18.5A -> this is under the 20A limit of the batteries, and so is safe.

For batteries connected "in parallel", you add up the max current (A) allowed instead, while the voltage units stay the same.

So if you have 2 x 3.7V 15A batteries in parallel, then the total current limit of the batteries is 30A (while the voltage rate in the equation is still 3.7V).

An example: 3.7V ÷ 0.2ohms = 18.5A -> this is under the 30A combined limit of the batteries in parallel, and so is safe.

Other Safety Tips to Avoid Thermal Runaway

Use a Battery Case
Vape batteries are unprotected, which means they're capable of conducting electricity and forming a circuit with anything metal.

This means that if you leave them loose in a pocket with coins and keys, you can easily burn yourself on your homemade circuit.

To avoid this issue, use a battery case made of rubber when they're not in use.

Turn Off Your Vape Kit / Auto Cut-Offs
Regulated vape mods contain an auto-cut-off feature after 10 seconds, which prevents them from overheating.

Your unregulated mod won't have this, so ensuring you switch it off manually is essential, to avoid burning yourself and damaging your mod.