Tested & Certified
SCIGOLD 21700 Li-ion Cells — Standard
SCIGOLD 21700 Li-ion rechargeable cells: 4,000 / 4,500 / 5,000 mAh, 3.6V, up to 18,000 mWh per cell. For high-output flashlights and bike lights.
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- Cell size
- 21700
- Power
- 3.6V Li-ion
- Material
- Protected button-top
- Cell models
- SL2170040 / SL2170045 / SL2170050
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on orders $35+
12-month warranty
from date of purchase
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30-day returns
original condition & packaging
SCIGOLD 21700 · 3.6V Li-ion
About 2× the energy of an 18650.
Protected button-top 21700s in 4,000, 4,500 and 5,000 mAh, up to 18,000 mWh a cell: about twice our 18650 Standard.
Inside the 21700
More energy in every slot.
Three capacities in one 21.9 × 71.0 mm cell, 12 to 15 A of discharge, and the same 3.6V nominal as our 18650 Standard.
Energy
About 2× the energy. About 1.5× the size.
At 21.9 × 71.0 mm against 18.5 × 65.3 mm, a 21700 takes about 1.5 times the volume of an 18650 (52% more) and holds about twice the energy: 5,000 mAh against 2,500 mAh for our 18650 Standard.
Our Cold-Weather 18650, at 3,500 to 4,000 mAh, narrows the gap.
- 4,000 mAh: 14,400 mWh, 12 A
- 4,500 mAh: 16,200 mWh, 13.5 A
- 5,000 mAh: 18,000 mWh, 15 A
Where it goes
High-output lights and battery boxes.
The 21700 suits high-output tactical flashlights, bike lights and work lights built for a removable 21700, and battery boxes and power-bank cases with spring contacts. Check the device's manual for the cell it needs.
- 4,000 mAh: the entry cell, for modern tactical flashlights
- 4,500 mAh: a balance of runtime and price
- 5,000 mAh: the longest runtime, for bike lights and expedition gear
Charging
Charges on the Bench Dock, beside your 18650s.
The SCIGOLD Bench Dock (CW401) takes 18650 and 21700 cells side by side across its four bays. Each bay detects its cell, applies the Li-ion charge profile, and shows live voltage and charging status on the LCD.
It runs from USB-C: a phone charger, a laptop adapter, a power bank or a car USB port.
Why this cell
Maximum energy per slot.
Up to 18,000 mWh
4,000, 4,500 or 5,000 mAh at 3.6V nominal: 14,400, 16,200 or 18,000 mWh a cell.
12 to 15 A
Discharge rated by capacity: 12 A, 13.5 A or 15 A.
Protected button-top
A built-in circuit guards against overcharge, over-discharge and short circuit. Certified to IEC 62133-2 and UN 38.3.
500+ cycles
Rated for 500+ charge cycles, with internal resistance of 22 mΩ or less (25 mΩ or less on the 5,000 mAh).
Compatibility
Made for devices sized for 21700.
- Bike lights
- Bike and e-bike lights that take a removable 21700.
- Flashlights
- High-output tactical flashlights that take 21700 cells.
- Battery boxes
- Battery boxes and power-bank cases with spring contacts, sized for 21700.
- Charger
- The SCIGOLD Bench Dock, alongside 18650 cells in the same charger.
Good to know
- Same 3.6V as our 18650 Standard, but not the same size: a 21700 will not fit an 18650 holder.
- Protected button-tops sit slightly longer than flat-tops. Allow a little extra length in tightly spaced slots.
- 3.6V nominal: about 4.2V full and about 2.5 to 3.0V empty. Rated from -20°C to 55°C.
- 21.9 × 71.0 mm; 66 to 69 g (± 2 g) per cell, depending on capacity.
Specs & details
Every number, in one place.
The larger cell many newer EVs and e-bike packs use.
Tesla’s Model 3 launched in 2017 on 2170 (21700-size) cells, where the Model S and X use 18650; many e-bike packs have moved to the larger cell since. The math is simple: same form-factor philosophy, about 1.5× the volume, about 2× the energy. SCIGOLD’s 21700 brings that cell format to the lights and gear you carry.
Pick your capacity
| Capacity (energy) | Max current | Best for |
|---|---|---|
| 4,000 mAh (14,400 mWh) | 12A | Modern tactical flashlights |
| 4,500 mAh (16,200 mWh) | 13.5A | Balanced runtime and price |
| 5,000 mAh (18,000 mWh) | 15A | Long-runtime needs, bike lights, expedition gear |
All three share 21.9 × 71.0 mm dimensions.
Where 21700 makes sense (and where 18650 still wins)
Pick 21700 if:
- Bike lights and work lights built for a removable 21700
- High-output tactical flashlights that take 21700 cells
- Battery boxes and power-bank cases with spring contacts, sized for 21700
- You want maximum energy per slot
Stick with 18650 if:
- Replacing cells in an existing 18650 device (flashlight, vape mod, headlamp)
- Battery holder is 18650-specific (21700 won’t physically fit)
- Cost-conscious — 18650 still costs less per cell (from $4.50 vs $7)
Compared to 18650
| Spec | 21700 | 18650 |
|---|---|---|
| Capacity range | 4,000-5,000 mAh | 2,000-2,500 mAh (Standard) / 3,500-4,000 mAh (Cold-Weather) |
| Energy per cell | 14,400-18,000 mWh | 7,200-9,000 mWh (Standard) / 11,690-13,360 mWh (Cold-Weather) |
| Size | 21.9 × 71 mm (about 1.5× the volume) | 18.5 × 65.3 mm |
| Weight | 66-69 g | 44 g (Standard) / 46-47 g (Cold-Weather) |
| Discharge current | 12-15A | 6-7.5A (Standard) / 21A continuous on the 3,500 mAh, 12A on the 4,000 mAh (Cold-Weather) |
| Use in modern devices | High-output flashlights, bike lights, work lights | Universal — legacy + current devices |
| Price per mWh | ~$0.0005 | ~$0.0007 (Standard) |
21700 is about 25% cheaper per mWh than the 18650 Standard but about 50% heavier per cell — pick by whether you’re optimizing for cost-per-energy or compactness.
Compatible with our Bench Dock charger
The Bench Dock takes both sizes automatically (4 bays, LCD per bay, auto-detect 3.6V Li-ion). One charger, both cells, no hardware swap.
Frequently Asked
Quick answers, before you buy.
How much more energy does a 21700 hold than an 18650?
What capacities do SCIGOLD 21700 cells come in?
Can I use SCIGOLD 21700 cells in an e-bike or scooter?
Are SCIGOLD 21700 cells protected button-top?
Is a 21700 cell a drop-in replacement for an 18650?
What devices use 21700 cells?
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