Battery Internal Resistance & Voltage Sag Calculator
EV acceleration battery analysis, power tool high-draw performance. Calculates loaded terminal voltage drop caused by battery cell internal resistance under high-amp draw.
Step-by-Step Derivation ▼ Show Steps
Calculations adhere to standard electrical engineering physics and National Electrical Code (NFPA 70) regulations.
Engineering Principles & Calculations
This calculator uses the exact mathematical relationships between Open Circuit Voltage (V), Load Current (A), Internal Resistance (mΩ) to determine Terminal Voltage (V), Voltage Sag (V), Heat Dissipation in Cell (Watts). In practical installations, factors such as ambient raceway temperature, harmonic distortion, duty cycle continuous operation, and conductor impedance must be accounted for by a certified electrician.
Calculates loaded terminal voltage drop caused by battery cell internal resistance under high-amp draw.
Typical Application & Industry Guidelines
EV acceleration battery analysis, power tool high-draw performance.
Battery Internal Resistance & Voltage Sag Calculator Benchmark Lookup Table
| Battery Chemistry | Typical Cell mOhms | 100A Voltage Sag @ 12V | Performance |
|---|---|---|---|
| Flooded Lead-Acid | 15 - 25 mOhms | 1.5V - 2.5V Sag | High Sag Under Load |
| AGM / Gel Lead-Acid | 8 - 15 mOhms | 0.8V - 1.5V Sag | Moderate Sag |
| LiFePO4 Solar Battery | 2 - 5 mOhms | 0.2V - 0.5V Sag | Very Low Sag (High Stability) |
| NMC Lithium-ion | 3 - 8 mOhms | 0.3V - 0.8V Sag | Low Sag |
| RC LiPo (High-C) | 0.5 - 2 mOhms | 0.05V - 0.2V Sag | Minimal Sag (High Inrush) |