This is actually a good question.
For example, if the question were about Z scale, they are rated at something like 7 volts.
T scale is rated at around 5.
Loved the car battery story....
Hey! It was 12 volts! Same as my power pack!
hahahaha.
But actually, it reminds me of my grandfather's old - what did they call it?- Standard Gage (sort of close to G scale- maybe smaller) from the 1910s or 20s. It ran off a big battery.