If you connect pin1 to anywhere that gets battery power when you turn on the master it will read battery volts. When the alternator is supplying power (and charging the battery), pin1 will read volts as supplied by the alternator. I don't think there is a place you can put it so that it reads battery voltage when the alternator is supplying power. Could be wrong. You can check battery volts by turning off the alternator switch when the engine is running.
I connected pin1 near the amps shunt. It was a convenient place.
The amps shunt is in position B so I can see the amps split between battery and system load with VP-X.