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1. 01

   Cell size has to match the mod

   18650 and 21700 are not interchangeable. The cell size your mod takes is stamped inside the battery bay. Order what's listed — not the closest size you can find.

2. 02

   Charge cells in a dedicated charger

   External chargers (Nitecore, Xtar, etc.) balance cell voltage and end at 4.20 V cleanly. Mods' USB-C ports do not — they're for finishing the tank, not full-cycling batteries.

3. 03

   Replacement glass + drip tips are model-specific

   Match the model name on the listing to your tank or mod. Even within one brand, sub-versions vary. Photos help when the model code is unclear.

1. 01

   Inspect the wrap before installing

   Any tear, rip, or burn mark in the heat-shrink wrap means the cell is unsafe. Rewrap or replace it — never carry naked cells loose in a pocket.

2. 02

   Charge cells in pairs (or as specified)

   Dual-cell mods need matched pairs — same brand, same age, charged together. Mixing pairs is the most common cause of imbalanced discharge.

3. 03

   Don't deep-discharge

   Cells should never drop below 3.20 V. Most mods warn first. Swap cells when the mod tells you to, not after the next session.

From the Vape Academy

More reading from the team.

• Choosing your first vape kit
• Complete beginner vape guide

Common questions

The honest answers.

• Are external batteries safer than internal ones?+

  Both can be safe with the right habits. External cells let you swap a tired battery without retiring the device, which is the main reason people prefer them. The trade-off is that you need a proper external charger and the discipline to inspect the wraps.

• Why ship batteries at storage charge?+

  Shipping regulations cap lithium-ion cells around 30 percent state-of-charge during transit. Charge them to full in your external charger before first use — never use them straight out of the package.

• Will this replacement glass fit my tank?+

  Only if the listing names your exact tank model. Even within one brand, sub-versions vary slightly. Cross-checking by capacity alone isn't reliable.

• What's the difference between a bubble glass and a flat glass?+

  Bubble glass holds 20 to 50 percent more juice for the same tank, at the cost of a wider profile that won't fit a sleeve case. Flat glass is the original spec. Both fit the same threads when the model name matches.