The label on a vape battery packs a lot into a few short codes: a model number such as 18650, two or three voltage figures, an amp rating and a capacity in mAh. This guide explains each one so you can pick up a cell and know what it is within half a minute.
Some background first. Vape batteries have worried and confused people for years, helped along by news stories about cells exploding and injuring their owners. The cells themselves are lithium-ion, the same chemistry used in phones, laptops, tablets, game controllers and medical devices.
Why vape batteries need more attention
Lithium-ion cells store a great deal of power, and most are tested heavily before they reach a shop. The difference lies in how they are handled. A phone, laptop or controller battery is built so that the owner barely touches it: you plug in a charger and wait. With a mod, the choice is yours. You decide on the type, the brand and the voltage of the cell that goes into the device, and for someone new to vaping that decision is intimidating and, done badly, dangerous.
Choosing the right type
As we said in our previous battery article, never put a cell into your device until you have confirmed it is suitable. Rechargeable AA and AAA batteries are NOT made for vape devices and should stay out of them.
The 18650 is the lithium-ion cell you will meet most often in vaping. Other sizes exist too, among them 10440s, 18500s, 18350s, 22500s and 22650s.
Decoding the model number
That model number describes the physical size of the cell, in three parts:
- First two digits: the diameter, normally 18 or 22.
- Next two digits: the height, for example 35, 44, 50 or 65.
- Last part: the shape, cylinder or non-cylinder.
Read that way, an 18650 has a diameter of 18, a height of 65 and a cylindrical shape. Cells of this size suit vaping because they supply the right voltage along with a suitably high-current discharge rate.
The electrical ratings
Voltage
A typical listing shows a 4.2 charge voltage, a 3.7 nominal voltage and a discharge cut-off of 2-3V. Each figure marks a point in the charge cycle:
- 4.2: the most the cell can hold. Never try to charge past it. Most external chargers have built-in protection and stop there anyway.
- 3.7: the nominal voltage, where the cell performs at its peak.
- 3V cut-off: as the charge drains, the voltage drops toward this level, and once it gets there your device stops firing.
Put a drained cell in an external charger and the display may show somewhere between 2-3 volts, which tells you it has to be recharged before it will fire again. The cut-off exists for a reason: trying to keep using a cell below the 3V mark can make it dangerous to recharge.
Amperage
Amperage is the battery’s current, meaning how fast its charge flows. Labels normally print it in the form “Max 40A”.
Wattage
Wattage combines the two previous figures. Multiply voltage by amperage to get it. A 3.7V cell rated at 40A works out to a maximum of 148W.
Ampere-hours and mAh
Capacity is printed in mAh. The cell on our desk says 3000mAh. To convert, take the ampere-hours (Ah) and multiply by 1000 to reach mAh.
Watt-hours
Watt-hours give you a way to compare cells that run at different voltages. The sum is volts x Ah = wH.
Internal resistance
A cell with high internal resistance can lose voltage while in use, an effect also referred to as voltage sag. As resistance rises, the cell has to work harder to deliver its power.
Where to buy
Plenty of vape shops, both physical and online, stock batteries. Stick to legitimate, trusted sellers. Problems are unlikely, but if one does come up you want to be able to trace the cells back to where they came from and get it resolved.
Brands: our writer’s view
What follows is one writer’s experience and opinion, not a test result.
- Personal pick: the purple Imren 40A 3.7v cell. It has given no trouble apart from the purple vinyl wrap beginning to tear and peel. It performs well in a two battery mod; owners of a 3- or 4-battery mod may want to look at other options.
- Also worth a look: 18650 cells from Sony, LG, Panasonic or AW.
- Rewrapped cells: according to our writer, companies including Efest, Aspire and Orbitronic take LG or Panasonic cells, remove the maker’s wrapper and apply their own coloured vinyl and name. The writer adds that these three have a reputation for overstating their specs to attract buyers.
- Avoid: TrustFire/UltraFire, or any brand with “Fire” in its name. Several reviewers have reported that low-grade, low-spec cells are bought cheaply and rebranded to look like premium ones on a par with LG and Panasonic. Our writer’s advice is to skip them, because a fire inside your mod is a real possibility, and to do your own research first even if a shop pushes you to buy them.
Wrapping up
Battery information can be dull and overwhelming, so this article covered one small piece of it: reading the numbers printed on the cell. That should be enough to judge whether the batteries you own are good ones or whether it is time to shop for replacements. The follow-up article covers safety ratings, battery chemistry and more on trusted brands.