GroundCloud recommends iPads be set to never “Auto-Lock” so the screens never turn off. With the screens always on it’s important to provide power to the iPads as the battery will not last a long shift. Most vehicles have a power port (cigar lighter) where an adapter can be used to provide a USB connector in conjunction with the Apple provided power cord like this:
RAVPower Dual USB Auto Adapter
Some vehicles do not have power ports. In this case it’s necessary to find a 12v power supply and hard-wire a step-down transformer to bring the voltage down from 12v to the 5v needed for USB powered devices. Fortunately this is easy & inexpensive to do:
12v to USB Step Down Converter
Connect the wires to a 12v DC source in the vehicle and then the Apple provided USB power cable to the other side.