Depot charging specifications frequently start from battery capacity, which is the wrong input. A vehicle with a large battery running short daily routes needs far less replenishment than its specification implies.
The number that matters is energy consumed per day divided by hours the vehicle is parked, and that arithmetic usually points at AC.
Start from duty, not from the battery
Daily distance, load, terrain, ambient conditions and auxiliary use determine energy consumed. That is what has to be replaced, and it is frequently a modest fraction of the battery.
Where telematics data exists, use it rather than estimating. Designing a depot against an assumed duty cycle produces oversizing, and oversizing at depot scale is expensive in both capital and supply.
Divide by the dwell window
Energy required divided by hours available gives the power needed per vehicle. A fleet returning in the evening and departing in the morning has a long window, and the resulting power requirement is usually well within AC capability.
Shortening the assumed window is the fastest way to inflate a depot's cost, and it happens whenever operations and engineering do not compare notes about actual departure times.
Where DC becomes necessary
That last case is worth checking specifically. A large commercial vehicle may have a limited AC acceptance rate regardless of battery size, which forces DC even with a long dwell.
- Short turnarounds, where vehicles return and depart within a couple of hours.
- Multi-shift operation, where the same vehicle is used around the clock.
- Opportunity charging during a route rather than at the depot.
- Vehicles whose onboard AC charger is too small for the energy required in the window.
Sequencing beats simultaneity
Not every vehicle needs to charge at once. Sequenced charging across the window, prioritised by departure time, supports the same fleet on a fraction of the connection that simultaneous full-rate charging would need.
This is the single measure that most often turns a depot supply upgrade into an avoidable cost.
Points can be fewer than vehicles
Where someone is on site to move vehicles, charge points can be shared across the fleet. Where nobody is, one point per vehicle becomes the practical requirement, because a vehicle that cannot be moved cannot free its point.
The labour cost of shunting overnight is the comparison against the capital saved, and it is a real cost rather than a rounding error.
Plan the failure case
A fleet that cannot start its shift is a business interruption, not a maintenance ticket. What happens when a point fails overnight, when a vehicle does not charge, or when the depot loses supply must be a design input.
Spare points, a defined escalation and enough margin in the schedule to recover are what turn a fault into an inconvenience.