These are regulated switching power converters, designed to allow the use of 12 volt equipment in 30to 90 volt vehicles. These are attractive, reliable, robust DC/DC converters good for fork lifts , off-road, construction and recreational equipment. To determine the amperage you would need add up the watts of all the equipment and divide by 12 volts.

These are also known as 48, 60 or 72 volt voltage reducers, and voltage regulators. They closely regulate the output voltage over a range of input voltages.