I am trying to make a simple battery tester for 1.5volt and 1.2volt batteries. I have googled circuit diagrams and found thousands. But none I can make any sense out of. If someone could assist me with a suitable link, this will be appreciated

 

The simplest one is a lightbulb on a little springy metal "c", like an elaborate paperclip, that allows you to just press the opposite ends onto the poles of the battery. Quick, easy, and a useful result from a very cheap device.

Another kind applies a small load and then lights an LED color that depends on the output voltage. A fancier one might use an LM3914 bar graph of 10 LEDs, or a meter. I prefer these latter types over the red/yellow/green ones, because of the slightly better resolution between batteries.

An elaborate, lab tester applies a loading profile over the discharge cycle and may be able to recharge and rerun multiple iterations of the test, with varied load profiles.

 

Here is what I use to test my AA batteries: a cheap volt meter and an incandescent lightbulb:

 

A breadboard! Nice.

This is comparable to the lightbulb tester I described, except that without the meter, brightness of the bulb is the lone measure of the voltage.

 

Yes, a real breadboard! I use this to demonstrate simple electrical circuits to elementary school children.

Notice the uncalibrated voltmeter is connected across the battery. The real visual test of the battery condition is to observe how much the needle drops when the knife switch is closed and the lamp load is connected.