Parallel vs Series Introduction
If you want to get a dual-battery mechanical mod but aren’t clear on the difference between a parallel and series battery configuration, this post is for you.
You do all the right things: you understand Ohm’s Law, battery limitations, safety and you confidently head to your local shop to look at some shiny new mods…
And that’s when things suddenly get cloudy as the salesperson shows you some mods, explaining that some are “series” and others are “parallel”. Great. You depart with your head spinning as you try to make sense of what you have found, and being the responsible vaper you are, you immediately head home to do more research.
Well, you landed here, where we will attempt to restore balance to your vaping world.
What is the difference between a parallel and series mod?
In the simplest of terms, the answer is voltage. There are other considerations critical to user safety and we’ll get to that later, but the key difference is voltage.
Note: In the following examples, let’s assume that we are using two identical 18650 batteries with 3.7 volts, max continuous discharge rating (CDR) of 20 amps, and 2000 mAh capacity each.
In this configuration, the batteries are working side-by-side with the positive terminals wired together and the negative terminals wired together. Remember, “wired” in this context merely means electrically connected, and you will generally not find any actual wires inside the mod.
In parallel, the resulting voltage is the equivalent to one of the batteries — in our example 3.7V. In a parallel circuit, current is split evenly between the two cells, effectively doubling the maximum CDR available to the coil and also doubling your battery capacity (run time) compared to a single battery. In our example, the max current available would be 40 amps, and the capacity 4000 mAh.
- Higher current capability
- Battery capacity / run time
- Lower voltage output
- Longer ramp time with heavy wire
- May run too cool for high-wattage vapers
Probably the best-known example of a dual-cell series box is the Wismec Noisy Cricket. A series battery configuration is just as described: the batteries are placed (or connected) end-to-end, one after another. The most common example of series battery usage outside of vaping would be a dual battery flashlight.
In a series configuration, the resulting voltage is additive — in our example 3.7V + 3.7V = 7.4V. The current in the circuit, however, is limited to the maximum CDR of a single battery or 20 amps since the same current is pulled through both batteries. Lastly, the life of our series configuration would also be the equivalent of a single battery or 2000 mAh.
- Higher voltage output
- Muscle to drive large wire mass
- Current limited to equivalent of a single battery
- Battery capacity / run time
- May run too hot for low-wattage vapers
Now the question is: which configuration is best for you?
The key thing to remember is that the same load (build) is going to behave very differently on each of these mods. For example: On a parallel mod at 3.7 volts, a 0.15-ohm load will pull 24.6 amps from your batteries and result in around 91.3 watts. The same load on a series box at 7.4 volts would pull over 49.3 amps and give you 365 watts — which of course is way outside of the safe limits of the batteries.
If you up the resistance of your build to 0.5-ohms, and use heavier wire — like clapton coils — the resulting load will pull 7.4 amps and deliver a mere 27.4 watts to your coils on a parallel mod. The coils will heat slowly, and the vape will be cool. On the series mod, the claptons will pull 14.8 amps and give you just under 110 watts, and the coils will ramp very quickly compared to the parallel box, giving you a much warmer and denser vape.
We recommend not going below 0.5 ohms when building for a series mod.
Safety first! Regardless of which configuration you decide on, always use a new pair of batteries, and keep them married. Mixing batteries of different brand, age, and capacity can be disastrous, especially in a series configuration. Both batteries in either configuration MUST be capable of delivering the required current simultaneously, if one battery cannot keep up, a thermal runaway may result in a battery venting and explosion. You don’t want to be “that guy” right? We don’t either.
Even with new, married batteries, the CDR of your batteries is another critical factor. Bear in mind that with a series mod, you will be limited to the CDR of a single battery while theoretically you can double that with a parallel mod.
Please read our series of articles on battery safety for an in-depth understanding of batteries and their limitations
Warnings aside, if you are a low wattage vaper who mainly uses single-wire coils and you are looking for longer run-time, consider the parallel mod. It will also give you more headroom by providing higher current limits.
If you prefer vaping at Mach 1 with your hair on fire (Maverick) while chucking some serious clouds, the higher-voltage series mod provides the necessary muscle. A series mod will easily drive larger wire mass, and ramp more quickly, while providing blazingly hot vapor — this mod dares you to tame it, just be mindful of your battery limits.
Whichever you choose, be safe and have fun.