Here is the circuit diagram of battery tester designed by Matthew B.. This circuit can be used to measure the 1.5V and 9V battery. The circuit is very-very simple and very easy to built since it uses five resistors and a panel meter only, and of course it is inexpensive too.
R1 = 18K Ohm
R2 = 240 Ohm
R3 = 8.2K Ohm
R4 = 3K Ohm
R5 = 10 Ohm
M1 = Panel Meter (Anyone will work)
Design Issues to consider:
It’s possible you have test with the values of R3 and R4 to have a precise reading from the meter. Every meter is different, so a little bit of experiencing using the resistor values is needed. Experiment by using a variable resistor instead of R3 & R4 to get a value of resistance that works.