mAh vs Wh: what is the difference?

mAh is charge, Wh is energy. Energy depends on voltage: Wh = (mAh/1000) × V. Use Wh when comparing batteries at different voltages or when a regulator is involved.

Why is my measured battery life lower than the estimate?

Common causes are higher real average current, regulator quiescent current during sleep, temperature derating, cutoff voltage limits, and battery capacity ratings that assume a lighter discharge rate than your application.

Why do coin cells brown out during a transmit burst?

Coin cells often have high internal resistance, so peak current causes a voltage droop (ΔV = Ipeak × Rint). Even if average current is low, a short burst can drop the voltage below your regulator or MCU minimum.

Bursts + sleep aware

Battery Life Calculator: Duty Cycle, Sleep Current, Regulator Loss

Estimate battery life from active and sleep current, duty cycle, battery capacity, and regulator losses. Useful for low-power embedded system design.

Quick start presets

Presets load example numbers to guide you—adjust them for your real measurements.

Inputs

Battery preset

Presets are starting points—validate with your real load profile.

Capacity (mAh)

Nominal voltage (V)

Internal resistance (Ω, optional)

Always-on current (µA, optional)

Power path

No conversion

Vout (V)

Efficiency (%)

Duty cycle

Cycle period (s)

Active duration (ms)

Active current (mA)

Sleep current (µA)

Include burst events (radio TX, motor, etc.)

Burst current (mA)

Burst duration (ms)

Bursts per cycle

Estimated lifetime

—

Avg battery current

—

Avg load current

—

mAh / day

—

Wh / day

Duty cycle

Sleep per cycle

Checks & notes

Adjust inputs to see instant updates.

Practical measurement tips

Sleep current

For µA sleep, use a dedicated meter or power profiler. Don’t forget LEDs, pull-ups, sensors in standby, and regulator quiescent current.

Bursts & peaks

For radio/motor bursts, measure with a shunt + oscilloscope (or a power analyzer). DMM averages can miss short spikes.

FAQ

mAh vs Wh: what’s the difference?

mAh measures charge, Wh measures energy. Voltage matters: Wh = (mAh/1000) × V. Use Wh when comparing batteries across voltages or when a regulator is involved.

Why is real life lower than the estimate?

Temperature, cutoff voltage, higher-than-expected average current, and regulator quiescent current are typical causes. Battery capacity is also specified under particular discharge conditions.

Coin cell brownouts during TX — why?

Coin cells can have high internal resistance, so a burst causes voltage droop (ΔV = Ipeak × Rint). Validate under low battery and cold conditions.

Battery Life Calculator: Duty Cycle, Sleep Current, Regulator Loss

Quick start presets

BLE Beacon

LoRa Sensor

Data Logger + SD

ESP32 Wi‑Fi

Used 30 min/day

Always‑on

Reset

Inputs

Power path

Duty cycle

Checks & notes

Practical measurement tips

Sleep current

Bursts & peaks

FAQ

mAh vs Wh: what’s the difference?

Why is real life lower than the estimate?

Coin cell brownouts during TX — why?

Related resources