Work out coin cell battery life instantly with clear inputs, formula shown and shareable results.
A CR2032 has high internal resistance — often over 10 ohms as it ages — so a 15 mA radio pulse causes a large voltage sag that can brown-out the device long before the capacity is used. Life comes from average current, but feasibility comes from the pulse behaviour.
Coin cell life
life = usable capacity / average current; usable is typically 60-75% because of rising internal resistance
Its internal resistance is tens of ohms when partly discharged. A 15 mA pulse then drops several hundred millivolts, tripping the brown-out detector.
A bulk capacitor of 10-100 microfarads across the cell supplies the pulse and recharges slowly between transmissions.