Easy to build volt meter using the an ic as a comparator , play with the voltage of the battery in the bottom left corner , green LED indicates good battery , red LED is bad , and so on 0-9 volts ideally , but you can play with the Pot value to change what kind of battery you want to test , this one is for a 9v battery , set to 3k ohms to test a 5v battery for
example
