Ok, so I’m sick of explaining battery safety. I mean I’ll always explain it, but I really wish that either vendors would explain it to people they sell mechs to or people would do some research before buying something they don’t know how to use.
This blog entry was started as a simple explanation of Ohms law, but as I’ve been getting asked questions, I’ve been adding more detail to it – so what this is, is a growing guide to vaping from the perspective of battery usage.
————————-Definitions and Terminology———————–
Mah – the Milliamp hours – The battery charge life. The higher this number, the longer your battery will last per charge.
Amp limit – Unless other wise stated, this is the Continuous current draw limit – the max current in amps that you can draw from your battery.
Nominal voltage – this is not actually the voltage present on your battery at full charge as so many believe, this is the voltage classification of your battery. 18650 batteries are classified as 3.7v batteries when in fact many will average around 4-4.2V on a full charge for the first 6 months of regular use with decent charging (only charge from nearly dead, not from the likes of 70%)
So if you have a 2000Mah 3.7v 20A battery, you have a battery life of 2000Mah (not bad) a nominal voltage class of 3.7v – so max charge around 4-4.2v depending on how good your battery is, and a max continuous discharge of 20A.
Continuous discharge versus pulse – by definition, anything less than infinity is a pulse discharge. Batteries are rated by continuous, that is, the max amps the battery can discharge, till it dies, without failing (going boom boom). A pulse discharge is a short burst, for vaping, usually less than 5 seconds. Now depending on the battery, the pulse rating will be higher than the continuous rating – for a 20A battery, i would usually put the pulse rating at 25A. Battery Mooch (link below) gives a Max vaping amps rating on his 18650 tests.
Mechanical (Mech) Mod – A device which is made up of no electronic components (without the battery) which has a connection between the battery and the atomizer. The device is fired by pressing a button which is usually spring or magnet operated. These devices are for advanced users only.
Hybrid Mod – A sub category of Mech mods, which typically have a 510 pin connector, with a Hybrid – the Atomizer has direct contact with the battery. This requires a protruding 510 pin. This devices are usually for advanced users who already have experience with Mech mods.
Regulated Mod – a mod with a regulator circuit which will give the same voltage output no matter your battery charge level. Where the power behind each “hit” is a tiny bit less than the one before, with a mech, as the battery drains; with a regulated mod, the voltage remains constant till the battery charge falls below a certain point needed to provide the desired level. Many regulated devices today are VV/VW mods – Variable Voltage/Variable Wattage, which allow you to adjust the volatage/power going through your coil. These mods are ideal for beginners as they can have built in safety features such as short circuit protection, low battery protection, excessive current protection and a fire cut off.
Now when you use a regulated mod – a mod with variable wattage or a circuit which determines its output based on the resistance for you, you don’t really have to worry. The device will limit your voltage so you cant go over a certain amp level.
Now thats not to say regulated mods are perfectly safe if misused.
If your mod is set to stop (by limiting your voltage) anything higher than a 25amp current but you’ve got some cheapo 5A panasonics (They’re still out there), your going to have a bad time.
Thats why most mods advertise that they require high drain batteries. Personally i’d recommend anything over 20A. But if your vaping a .5 ohm coil at 30 watts you dont have much to worry about – with regulated mods, like most things, they only really become dangerous when your pushing their limits.
If you want to learn more about calculating amp limits for regulated mods (its different to mechanical) this is a good article to start you out – Calculating current for a regulated mod.
As a general rule – if your building coils or vaping below .5 and above 30 watts you need to research battery safety. All vapers would in an ideal world but its not an ideal world.
When you use a Mechanical or unregulated mod however, you need to determine the resistance to suit the spec of your batteries based on their output – the user variable changes from voltage (which is what wattage controls in regulated) to resistance.
The way it works is – the current drawn from the battery is based on how much resistance is in the circuit – less resistance, more current flow, more resistance, less current flow. The voltage is the “force” behind the flow so to speak (not strictly speaking true but works for this basic description), the more volatge, the more current.
————————Calculating Ohm’s Law————————
To relate the Voltage, Current and Resistance together, we use Ohm’s Law.
We use it as follows (this is an exert from one of my own FB posts – I’m not retyping it because as i said, I’m sick of having to re do it):
Ohms law is V=IR
V is voltage in volts
I is current in amps
R is resistance in ohms
It states that the voltage is equal to the current multiplied by the resistance.
For vaping mechs we swap this around to
Voltage divided by resistance = the amps.
So on a parallel box you will have 3.7v – 4.2v (same voltage as a single 18650 mech. Series boxes will have about 7.4-8.4v depending on batteries).
I normally take 4.2v for my calculations assuming its a good, new battery by a decent company.
Lets say you are using a samsung 25r which can handle about 25amps. And a .2 build (which is crap on a parallel box but this is just an example)
So this means there are 21 amps of current being drawn from the battery by the coils. As the battery is rated for 25 amps and you are below this – it is safe to vape.
Battery Mooch has an excellent chart for checking the Specs of 18650 batteries: