The madgenius
I hope that you just misspoke when you said that you put the 10 ohm resistor in the positive line when you measured the battery voltage.

What Campgems said was that he put the resistor across the leads of the battery, which is the correct way to do it. This way the 10 ohms is in parallel with the meter and represents the load to the battery. The meter reads the drop across the load.

What happens when you put the resistor in series with the positive lead is that you don’t put hardly any load across the battery at all. The input impedance of typical good quality meter is about 1,000,000 ohms. If you put that in series with a 10 ohm resistor you get a total resistance of 1,000,010 ohms. That does not represent a load to the battery. What you will read on the voltmeter is basically the no load terminal voltage.

A simple test will demonstrate what I am saying. Read the no load voltage on the battery under test. Then put a 10 ohm resistor in series with the positive lead and read the voltage again. The voltage will be the same. Next put the resistor across the battery positive and negative leads and read the drop across the resistor and you will get a lower voltage which is the loaded voltage of the battery.