Seriously - you're not supposed to read battery voltage by simply connecting the plus and the minus with the multimeter? Wow - i've been doing this for years... Gives me a good indication of how full the batteries are...
There is nothing wrong with measuring the battery voltage
like this. However, if you take the trouble to actually read the rest of the thread the poster was measuring the CURRENT
from a battery by simply connecting the plus and minus of a multimeter across the battery.
If your dad actually taught you that trick then he was presumably in the business of selling either batteries or multimeters.