How to read a vape battery wrap, and how to spot a fake cell

The size and chemistry code is the key. In INR18650, the I means lithium-ion, the N is the main cathode material (nickel), and the R means round. You may also see IMR (manganese) or ICR (cobalt). The numbers are the size, covered in our cell size guide.

Next comes capacity in mAh, the nominal voltage (3.6V or 3.7V), and on many vape cells a continuous amp rating. Genuine cells often carry a batch or date code too.

Many big cell makers sell their cells bare to manufacturers, so the wrap you see may come from a reseller. That is normal, as long as the numbers printed match the cell's real datasheet.

The fastest fake test is the mAh figure. Genuine 18650s top out at roughly 3500 to 3600mAh, and those highest-capacity versions are low-drain cells not meant for high-wattage vaping. High-drain vape cells sit closer to 2500 to 3000mAh.

So when you see an 18650 wrap promising 5000, 6800 or 9900mAh, you can stop reading. Those cells are usually much smaller and often salvaged, sometimes with sand or filler packed in to make up the weight. Their real capacity is often a fraction of the sticker and their amp rating is anyone's guess.

The same logic applies to 21700s: genuine vape-grade cells typically sit around 4000mAh, and the very highest real figures are around 5000mAh at low drain.

One red flag is a reason to look harder. Two or more and the cell belongs in a recycling bin, not your mod. The weight check is the one most people skip, and it is the most telling: a genuine 18650 typically weighs around 45 to 48g, while a fake built around a smaller cell often feels noticeably light.

Look at the print as well. Genuine wraps have crisp, even text and consistent fonts. Fakes often have smudged lettering, spelling mistakes, or a wrap that does not sit flush at the ends. Peel back the very edge of the top and you sometimes see a different wrap underneath.

Price is the last clue. A cell far cheaper than everyone else's is cheap for a reason.

There is a grey area between genuine and fake. Some sellers buy real cells, shrink their own branded wrap over the top and print a new set of figures. The cell inside might be perfectly decent, but the amp rating on the new wrap is often inflated well beyond the original maker's figure.

A rewrap is only as trustworthy as the seller. Reputable ones say which original cell is inside and quote its real rating. If a brand you have never heard of claims ratings that no major cell maker publishes, assume the numbers are wishful.

The simplest fix is buying from an established UK vape shop that sources cells properly. Browse our 18650 batteries and check every listed rating against the CDR you actually need.

If you already own cells you are unsure about, an analysing charger settles it. Many external chargers have a capacity test mode that fully charges the cell, discharges it at a set rate and reports how many mAh it actually delivered.

A genuine 3000mAh cell will test fairly close to its rating when new. A fake claiming 9900mAh might struggle to reach a fraction of that. You can also watch the resting voltage: a healthy cell taken off the charger at 4.2V should still be sitting very close to that a day later.

Any cell that tests badly, loses voltage fast at rest or gets warm on the charger should be recycled, not used up.