Close switch after starting!
This circuit is a good way to get an accurate measure of battery life by loading it as it would be in a real circuit, batteries have internal resistance which increases as it is discharged which is why measuring a battery open circuit can give false results, this circuit can also be used to measure the capacity of the battery, a worn out battery will have reduced capacity resulting in fast discharge.
The circuit consists of a constant current source set by the lower potentiometer and a comparator which lights a LED when the voltage falls below a set point, this is set by the upper potentiometer, this circuit is designed for 5V operation up to 2A but can be adapted for any voltage and current.
