✱ RenderVapcell T39
At 3900 mAh, this ranks #63 of 72 21700 cells in our database. On the lower end for capacity among 21700 cells. A mid-range 21700 cell. Solid for builds that don't need extreme capacity or discharge.
Photos from the community
See the wrap, markings, and terminals up close.
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Full specifications
| Electrical | |
|---|---|
| Chemistry | NMC |
| Nominal voltage | 3.6 V |
| Max charge voltage | 4.2 V |
| Discharge cutoff | 2.5 V |
| Max continuous discharge | 35A (Mooch-tested) |
| Mooch CDR (trusted) | 35 A |
| Standard charge current | 3000 mA |
| Internal resistance | 6 mΩ |
| Physical | |
| Form factor | 21700 |
| Dimensions | 21.1mm × 70.5mm |
| Weight | 68 g |
| Top type | Flat Top |
| Protected | No |
| Wrap color | Red |
| Performance | |
| Capacity | 3900 mAh |
| Energy | 14.04 Wh |
| Specific energy | 206.47 Wh/kg |
| Energy density | 569.54 Wh/L |
| Power density (gravimetric) | 1,853 W/kg |
| Power density (volumetric) | 5,111 W/L |
Independent test data: Mooch's test of the T39 ↗
At the standard 3000 mA charge rate, a full charge takes about 1.3 hours. The last bit is a slow taper to top it off.
Voltage operating window
2.5VNominal
3.6VMax charge
4.2V
Usable range: 1.7V
C-rate conversion: Vapcell T39 (3900mAh)
| C-Rate | Current (A) | Theoretical runtime |
|---|---|---|
| 0.2C | 0.78 A | 5h 00m |
| 0.5C | 1.95 A | 2h 00m |
| 1C | 3.9 A | 1h 00m |
| 2C | 7.8 A | 30m |
| 3C | 11.7 A | 20m |
| 5C | 19.5 A | 12m |
| 8C | 31.2 A | 7m 30s |
Highlighted row is closest to the rated 35A continuous discharge.
Charging
| Rate | Current | Estimated time |
|---|---|---|
| 0.5C | 1,950 mA | ~2h 00m |
| Standard | 3,000 mA | ~1h 18m |
| 1C | 3,900 mA | ~1h 00m |
These are estimates for the constant-current phase. Real charge time is a bit longer because of the slow taper at the end.
Datasheet
Pack scaling
Series voltage configurations
| Config | Nominal V | Max V | Min V | Common use |
|---|---|---|---|---|
| 1S | 3.6V | 4.2V | 2.5V | Flashlights, single-cell devices |
| 2S | 7.2V | 8.4V | 5V | RC vehicles, 7.2V packs |
| 3S | 10.8V | 12.6V | 7.5V | Power tools (10.8V nominal) |
| 4S | 14.4V | 16.8V | 10V | Ebike (small), some power tools |
| 7S | 25.2V | 29.4V | 17.5V | Ebike (24V system) |
| 10S | 36V | 42V | 25V | Ebike (36V system) |
| 13S | 46.8V | 54.6V | 32.5V | Ebike (48V standard) |
| 14S | 50.4V | 58.8V | 35V | Ebike (52V high-power) |
| 16S | 57.6V | 67.2V | 40V | DIY powerwall |
Parallel capacity scaling
| Config | Capacity | Energy | Max discharge |
|---|---|---|---|
| 1P | 3,900 mAh | 14 Wh | 35 A |
| 2P | 7,800 mAh | 28.1 Wh | 70 A |
| 3P | 11,700 mAh | 42.1 Wh | 105 A |
| 4P | 15,600 mAh | 56.2 Wh | 140 A |
| 5P | 19,500 mAh | 70.2 Wh | 175 A |
| 6P | 23,400 mAh | 84.2 Wh | 210 A |
Example pack configurations
Design a custom pack with this cell:
Application suitability
Physical dimensions
Similar cells
Same format and chemistry, within ±500mAh capacity:
| Cell | mAh | CDR | Wh | Weight | Wh/kg |
|---|---|---|---|---|---|
| Vapcell T39 (this cell) | 3900 | 35A | 14.04 | 68g | 206.47 |
| Xtar XTAR 30A 4200mAh | 4200 | 30A | 15.1 | 70g | 216 |
| Hohm Tech Hohm Run XL | 4007 | 30A | 14.4 | — | — |
| Ampace JP40 | 4000 | 60A | 14.4 | 69g | 209 |
| Enercig EC-2174HC | 4000 | 30A | 14.4 | 70g | 206 |
| EVE INR21700-40P | 4000 | 35A | 14.4 | 70g | 206 |
Build with this cell
Frequently asked questions
Handling and safety
Lithium cells can be dangerous if mishandled. A few things to keep in mind:
- Never charge above 4.2V or discharge below 2.5V.
- Store cells at around 3.6-3.8V (roughly 40-60% charge) for long-term storage.
- Don't mix cells with different capacities, chemistries, or states of charge in a pack.
- Inspect wraps before use. A torn wrap can cause a short circuit.
- Always use a BMS or balance charger appropriate for your pack configuration.
- Keep cells away from metal objects, keys, and coins. A short across the terminals can cause fire.
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Specs come from manufacturer datasheets and independent testing; Mooch-tested discharge ratings are shown when available because they reflect real continuous performance better than headline datasheet numbers. Browse the full 18650 & 21700 cell database to compare every cell.
Disclaimer: We do our best to keep the information on this page accurate, but we cannot guarantee that all specifications are correct or up to date. Cell characteristics can vary between production batches and may change over time. Do not rely solely on this data for safety-critical applications. Always verify against the manufacturer's official datasheet before use.