A battery that delivers the correct voltage is essential for almost all vehicles. Deliver too much voltage and components either move or spin too fast, or they overheat and burn out. Deliver insufficient voltage and moving components slow down, or don’t work at all. Jump-starting a 24-volt system from a 12-volt system won’t work if only one 12-volt battery is available, but if the 12-volt truck has two batteries, it becomes possible to produce a 24-volt supply.
Position the 12-volt truck as close to the 24-volt truck as possible. Orientate the vehicles so their batteries are as close to each other as possible. For example, if both vehicles have side mounded batteries, park the trucks side by side, and if the batteries are housed in the engine compartment, park them nose to nose.