Is the wiring correct on this battery tester ? I assumed that you would have a positive feed to one side of the meter, and the negative feed to the other side. This circuit however connects the positive feed to both sides of the meter, albeit with a resistor inbetween. Is this correct ?
Unfortunately with the quality of the picture it is difficult to tell anything. However the battery is probably connected to the meter through a voltage divider with the meter reading voltage drop across the resistor while a slight load is applied to the battery. And this is likely doubled so that a battery can be read in both polarities.
Not a very useful tester though because it isn't able to apply enough load to a battery to get a meaningful measurement unless all of your loads are slight.