These energy guidelines (for a generic battery) can help size the battery capacity required, based on the truck and the application. The examples below refer to a lead-acid battery:

Total Energy (kWh) = Battery Voltage (V) x Battery Capacity (Ah)

E.g. 48V x 400 Ah = 19200Wh or 19.2 kWh

Total energy x maximum DoD%(kWh) = Total Energy (kWh) x 80% ( considering 20% lower limit for discharge)

E.g. 19.2kWh x 80% = 15.4 kWh

Power (kW) = Energy used per unit time ( kWh/h)

E.g. if you use all the energy in 1 hour, you would be consuming 15.4 kWh/h

E.g. if you use all the energy in 5 hours, you would be consuming 3 kWh/h

Energy consumption expressed as kWh/h

E.g. For a 3-Wheel CB Truck J1.6XNT, energy consumption on VDI 2198 test course is 4.2 kWh/h.
A 48V 400 Ah battery will last 3.7 hours

In reality trucks rarely use as much power as the VDI test course would suggest

A more accurate energy consumption can be measured using a battery logging device

Idle time (%) is the time when the truck is in use but energy from the battery is not used

E.g. includes paper work, manual loading/unloading, picking , getting on and off the truck