Vape Battery Safety Calculator
Verify your build is safe for your batteries before you use it. Calculate amp draw, check CDR headroom, estimate battery runtime, and get safety recommendations.
Battery Safety Essentials
DO
- • Use batteries from reputable manufacturers
- • Stay within your battery's CDR with 20% headroom
- • Inspect battery wraps regularly for damage
- • Store batteries in cases when not in use
- • Use a dedicated battery charger
- • Marry batteries used in multi-battery mods
DON'T
- • Never exceed your battery's CDR
- • Never use batteries with torn wraps
- • Never carry loose batteries in pockets
- • Never leave charging batteries unattended
- • Never use mismatched batteries in series/parallel
- • Never charge batteries overnight
Understanding Battery Specifications
CDR (Amps)
Continuous Discharge Rating. Maximum safe current the battery can deliver continuously.
Capacity (mAh)
How much energy the battery holds. Higher = longer runtime, but often means lower CDR.
Voltage
18650/21700 cells range from 4.2V (full) to 3.2V (low cutoff). Nominal voltage is 3.7V.
Configuration
Parallel doubles CDR. Series doubles voltage. Dual parallel gives 2x CDR at same voltage.
Popular Battery Recommendations
| Battery | CDR | Capacity | Best For |
|---|---|---|---|
| Sony VTC5A (18650) | 25A | 2500mAh | High-drain, mech mods |
| Molicel P26A (18650) | 25A | 2600mAh | High-drain, excellent |
| Samsung 25R (18650) | 20A | 2500mAh | All-around good choice |
| Samsung 30Q (18650) | 15A | 3000mAh | Regulated mods, runtime |
| Molicel P42A (21700) | 30A | 4200mAh | Best 21700 all-around |
| Samsung 50E (21700) | 10A | 5000mAh | Low-wattage, max runtime |
Frequently Asked Questions
What is CDR and why does it matter?
CDR (Continuous Discharge Rating) is the maximum current your battery can safely deliver continuously. Exceeding the CDR causes overheating, which can damage the battery or cause venting. Always use batteries with a CDR higher than your maximum amp draw.
How do I calculate amp draw for a regulated mod?
For regulated mods: Amp Draw = Wattage / (Battery Voltage × Efficiency). We use the low voltage cutoff (3.2V) as the worst case, with 90% efficiency. For example, 100W at 3.2V with 90% efficiency = 100 / (3.2 × 0.9) = 34.7A.
How do I calculate amp draw for a mechanical mod?
For mechanical mods: Amp Draw = Voltage / Resistance. Use 4.2V (full charge) for maximum amp draw. For example, a 0.2Ω coil at 4.2V = 4.2 / 0.2 = 21A. Always calculate at full charge for safety.
What's a safe CDR headroom?
We recommend at least 20% headroom below your battery's CDR. This accounts for battery degradation, resistance measurement tolerances, and brief power spikes. More headroom is always safer.
How do parallel batteries affect amp draw?
Parallel batteries share the current load. Two batteries in parallel effectively double your CDR. For example, two 20A batteries in parallel can safely deliver 40A total. Series batteries add voltage but don't increase current capacity.
What batteries are best for vaping?
For high-drain vaping, look for batteries with 20A+ CDR from reputable manufacturers (Samsung, LG, Sony/Murata, Molicel). Popular choices include Samsung 25R (20A), Samsung 30Q (15A), Sony VTC5A (25A), and Molicel P26A (25A). Always buy from trusted vendors.
How is battery runtime estimated?
Runtime depends on battery capacity (mAh), wattage, and usage patterns. Our calculator estimates based on: puffs = (capacity × voltage × 0.8) / (wattage × puff duration). The 0.8 accounts for usable capacity before low voltage cutoff.