@JvB just based on the product images, the batteries have to be button cells. I am guessing that they take 2 or 3 of them each.
I only found one place that had battery information listed. It was an ebay listing where the seller probably just entered the first things that came to mind.
Battery : A
Voltage: 0.5 volts
I don’t know of any commercial battery chemistry with a rated output of 0.5 volts.
In the vacuum tube days, the A batteries were the high voltage supply and B batteries were for the heaters in the cathodes. The designation was for the job the battery did, but not the specific size, shape, or voltage. “A” batteries were often 45 volt, 60 volt, 75 volt, or 90 volts, but other values existed. 0.5 volts was never an option.
When a standards group met to come up with standard battery sizes they used AA, C, and D, but didn’t use A or B.
There were some obvious safety issues with 90 volt batteries, so some radios used a pair of 45 volt batteries instead.
Wow this was in my last IRK
The thing was seven feet tall, its back covered in a patchwork of blonde, brown, and black hair. It stood on two legs, ending in rough cloven hooves. Its body was misshapen and lumpy, a melted mass of plastic. On top of the thing, there was a goat-like head covered in small painted eyes. Several stubby arms sprouted from the forehead to create a twisted facsimile of horns. It cried out again, tiny limbs across the body bristling out over the throat.
Batteries nearly dead in the first one I opened. Completely dead in second one. Both went straight into the trash. Worst junk I’ve ever bought on here. Not even worth sending back or trying to find batteries for.