Tools you might need next
Decode resistor color bands to resistance value in ohms or find the correct color bands for a target resistance and tolerance.
Calculate current-limiting resistor value and wattage for LED circuits from supply voltage, forward voltage, and desired current.
Calculate output voltage and resistor values for voltage divider circuits from input voltage, R1, R2, and load considerations.
Capacity divided by constant current gives hours if voltage stays usable.
hours = capacity (Ah) / load (A)High pulsed loads reduce effective capacity on some chemistries. Use average current for a first estimate.
Devices stop before battery is chemically empty. Derate 10% to 30% for regulator dropout and safety margin.
Updated: July 2026
Average 80 mA active and 20 µA sleep to estimate weeks on 3400 mAh cell.
See runtime at 500 mA draw from 10,000 mAh rated pack.
Compare standby microamp draw vs. annual replacement schedule.
Duty-cycle Wi-Fi or LoRa bursts. Weight by time on vs. sleep.
Conversion losses and internal cell voltage matter. Derate advertised capacity.
Estimate how long your project runs on a charge. Enter battery mAh and average load current to get theoretical runtime and practical derated hours.