My Montero 2012 shows in my battery tester gadget the ripple test of 0.480 V. Is this normal or is it a bad sign?

Sometimes when I am in the NLEX with speed of around 90-100, there is a noise, looks like coming from the aircon belt, but when I turn-off the aircon, the noise disappears immediately. I don't know if this is related to the high ripple that I get from the car battery tester.

Any helpful comments is highly appreciated!