How to read the voltage of a bunch of batteries in parallel?
If you have just one battery in series with one resistor, then the circuit is already in Thevenin equivalent form.  The output voltage with no load is simply the battery voltage since no current flows through the resistor as the circuit is not complete. With five circuits in parallel, the Thevenin resistance is just the parallel combination of the five resistors.  Since they are identical, the Thevenin resistance if 1/5 the value of one resistor. The Thevenin voltage can be found by just shorting out four of the batteries and calculating the output voltage and then multiplying the result by five since there are five identical circuits.  The result is equal to the voltage of one battery. The overall effect of putting five identical circuits in parallel is to reduce the Thevenin resistance by a factor of five but with the same Thevenin voltage. The only way the output voltage would be zero is if you short the output.  Then all of the battery voltage appears across the resistor.