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21700 Batteries 🔋

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21700 Batteries

Next-Generation Capacity and Output

21700 lithium-ion batteries provide higher energy and current capability than 18650 cells, in a slightly larger format measuring approximately 21 mm × 70 mm. Typical nominal voltage is 3.6–3.7 V (up to 4.2 V when fully charged), with capacities commonly in the 4000–5200 mAh range, model-dependent.

Performance & Chemistries

Modern chemistries such as INR/NMC and NCA deliver an excellent balance of energy density, cycle life and current capability. Continuous discharge ratings vary by cell (e.g., 10–45 A), so choose a model that matches your device’s draw.

Applications

Ideal for high-output LED torches, e-mobility packs (some e-bikes/scooters), portable lighting, and even some vapes. Many newer devices have moved to 21700 for the extra runtime and performance—always confirm your device’s specification.

Compatibility & Sizing

Check whether your device requires button-top or flat-top, and whether it specifies protected or unprotected cells. Note that protected 21700 cells are longer and may not fit tight battery bays.

Charging & Safety

Charge only with a compatible Li-ion charger set for 4.2 V termination. Use matched cells in series/parallel devices. Do not mix old and new cells. Store partially charged for long periods and avoid charging unattended.

Key Features
  • Rechargeable Li-ion 21700 format (21×70 mm)
  • Nominal voltage: 3.6–3.7 V (4.2 V max charge)
  • Typical capacity: 4000–5200+ mAh (model dependent)
  • Discharge ratings up to 45 A (check device needs)
  • Available in button-top / flat-top; protected / unprotected
  • Excellent for high-output torches and pro equipment
FAQs
21700 cells offer more capacity and often higher current capability, giving longer runtime or higher output in compatible devices.
Yes. The protection circuit adds length. Some devices cannot accommodate protected cells—check your battery bay and the manufacturer’s guidance.
Some devices require a raised positive terminal (button-top) for reliable contact; others are designed for flat-top cells. Check your device contacts.
Use a quality Li‑ion charger supporting 21700 size and 4.2 V termination. Set an appropriate charge current and remove cells when full.
No. Use matched cells of the same brand, model and age, especially in series/parallel configurations.

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