How to test battery level with Arduino?

Hey there,

I have done this to do a health check on a car battery. But I am facing a problem. My circuit works perfectly, I get the same reading on my arduino as with the multimeter. But I get like 14.15 volts on a car battery that has some proper load on it (camp fridge). I was expecting the load to drop the volts down to 12.5 or something more accurate. I store bought battery monitor shows 12.2volts. Lefty mentioned earlier that load should give more accurate readings. Am I missing something?