Battery Life Calculator

Battery Life Estimation projects the operating lifetime of an embedded system, factoring in battery configuration and circuit efficiency.

Formulas:

• Parallel Capacity: Total_Capacity = Single_Capacity * N_Parallel
• Estimated Runtime (hours): Total_Capacity * (Efficiency / 100) / Load_Current
• Self-Discharge: Capacity_Remaining = Initial * (1 - Rate_per_Month)^Months
• Avg Current (duty): I_avg = Σ (t_k / Σt) × I_k
• Modes: Simple (single I), Advanced (Sleep/Active), Most Advanced (Sleep/Collect/Process/Transmit)

Usage: Input battery capacity, average load current, regulator efficiency, and parallel count to estimate operational life.

When you need it: Estimating how long a battery lasts from its capacity and the load's average current, including derating for high-drain loads and duty-cycled MCUs.

Worked example: A 2000 mAh pack at a 50 mA average draw lasts 2000 / 50 = 40 h in the ideal case. Real runtime is capacity × derate / I_avg, so include sleep current in the average.

Tips & gotchas:

• Use a true duty-weighted average current — a device that sleeps 99% of the time is dominated by sleep draw.
• Peukert's law cuts effective capacity as discharge rate rises; a "2000 mAh" cell delivers less at high current.
• Cold temperature and end-of-life ageing both reduce usable capacity — budget margin.
• For long standby, self-discharge and the regulator's quiescent current can exceed the load itself.