# Understanding Drone LiPo C Rating and Real Power Output
Choosing the correct LiPo battery for an FPV drone or RC aircraft requires understanding the relationship between battery capacity, C rating, and motor current consumption. While battery manufacturers frequently state C ratings of 100C or 150C, real-world continuous discharge capabilities are bounded by internal resistance and thermal dissipation limits. This calculator evaluates realistic continuous discharge amperage, providing drone pilots with accurate power headroom predictions.# Comparison of RC Battery Chemistries
| Chemistry | Nominal V | Max Cell V | Energy Density | Peak Discharge | Best Use Case |
|---|---|---|---|---|---|
| LiPo (Standard) | 3.7V | 4.20V | High | 100C - 150C | 5-Inch Freestyle and Racing FPV |
| LiHV (High Voltage) | 3.8V | 4.35V | Very High | 80C - 120C | TinyWhoops and Micro Quads |
| Li-Ion (18650/21700) | 3.6V | 4.20V | Maximum | 15C - 35C | 7-Inch Long Range Endurance |
| LiFePO4 | 3.3V | 3.65V | Moderate | 30C - 50C | Ground Stations and Field Chargers |
# Impact of Voltage Sag and Internal Resistance on Quadcopter Performance
Voltage sag is the sudden drop in battery voltage experienced under heavy throttle acceleration. As current passes through the internal resistance of each cell, energy is converted into heat instead of thrust. A battery with higher internal resistance will suffer severe sag, triggering low voltage warnings on the FPV OSD telemetric display even when battery capacity remains high. Monitoring cell resistance in milliohms is essential for diagnosing aging or degraded LiPo packs.- Low Internal Resistance (1-4 mΩ per cell): Excellent punch, minimal sag, cool running temperatures.
- Moderate Internal Resistance (5-10 mΩ per cell): Standard freestyle performance, slight sag under full throttle.
- High Internal Resistance (>12 mΩ per cell): Noticeable power loss, severe sag, battery gets hot quickly.