Battery C Rating Calculator
Max discharge (A)
500.0
How it works
LiPo battery C rating specifies how fast a battery can safely discharge. The Battery C Rating Calculator converts C ratings to maximum continuous and burst current in amps, and determines if a battery is adequately rated for a given motor system.
**C rating formula** Maximum continuous current (A) = battery capacity (mAh) / 1,000 x continuous C rating. A 1,500mAh 30C battery: 1,500 / 1,000 x 30 = 45A maximum continuous discharge. Burst C rating (often 2x continuous) applies for 10 to 15 second peaks only.
**Motor system matching** Sum the maximum current draw of all motors at full throttle. Add 20% safety margin. Compare to battery's continuous C rating. If total motors draw 60A at full throttle: you need at least 72A continuous battery rating. At 1,500mAh: 72A / 1.5Ah = 48C minimum battery.
**C rating skepticism** Published C ratings are frequently inflated by manufacturers. A conservative rule: treat advertised C ratings as 60 to 70% reliable. Name-brand batteries have more accurate ratings than no-brand equivalents.
**Battery health monitoring** LiPo puffing (cell expansion) indicates cell damage — stop using immediately. Check resting voltage after storage: 3.8V per cell = healthy storage charge. Values above 5 to 6 milliohms per cell on internal resistance checks indicate aging or damaged cells.
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Frequently Asked Questions
- The 'S' designation indicates the number of lithium polymer cells connected in series. Each LiPo cell has a nominal voltage of 3.7V and a fully charged voltage of 4.2V. Cell counts: 1S = 3.7V nominal / 4.2V max. 2S = 7.4V / 8.4V. 3S = 11.1V / 12.6V. 4S = 14.8V / 16.8V. 6S = 22.2V / 25.2V. Higher voltage allows motors to produce more power at the same current draw (Power = Voltage × Current). Running higher voltage is more efficient for a given thrust level — 6S systems draw less current for the same thrust as 4S, reducing heat and extending component life. 'P' designations (2P, 3P) indicate cells in parallel — this increases capacity (mAh) without changing voltage.
- Never puncture, cut, or throw a LiPo battery in regular trash — undischarged lithium batteries are a fire and chemical hazard. Safe disposal: completely discharge the battery first to below 3.0V per cell. Method 1: discharge through a load resistor (a 12V incandescent bulb connected to battery terminals discharges slowly and safely). Method 2: use a charger in discharge mode. Method 3: for heavily damaged batteries — submerge in a 5% salt water solution in an outdoor area away from combustibles. Bubbles and some heat will occur as cells discharge slowly through the salt water electrolysis. Once no bubbles remain for 24 hours, the battery is discharged. Then dispose at a battery recycling facility or hazardous waste collection site.
- Puffing occurs when lithium-ion chemistry produces gas (typically from electrolyte decomposition). Causes: over-discharge (below 3.0V per cell under load causes electrolyte breakdown), overcharge (above 4.2V per cell per accurate charger calibration), excessive current draw exceeding the battery's actual C rating, physical damage, age and cycle count, and storage at inappropriate temperature. A slightly puffed battery (soft, not rigid) has reduced capacity and increased internal resistance — performance is degraded but it may still function. A significantly puffed battery (rigid, noticeably expanded) should NOT be used — risk of thermal runaway during charging or under load. Never charge a puffed battery unattended or inside a building.
- Quality LiPo batteries (Tattu, Gens Ace, CNHL) typically provide 200–400 charge cycles before capacity drops to 80% of original. Factors extending cycle life: charge to 4.1–4.15V per cell instead of 4.2V (reduces capacity by ~5–8% but doubles cycle life), discharge to 3.5V per cell under load rather than 3.3V, keep storage voltage at 3.8V per cell, store at room temperature. Factors reducing cycle life: consistently using full C rating, heat exposure during charging, discharging below 3.3V, physical impacts. When to replace: capacity has dropped significantly (noticeably shorter flights), internal resistance has risen above 5–8 mΩ per cell, puffing, or any inability to maintain voltage under normal load.