Fleet charging depot planning: a duty-cycle worksheet

Plan from the duty cycle, not the vehicle count

Ten vehicles with long overnight dwell differ from ten vehicles returning briefly between shifts. For each vehicle group, record route distance, expected energy use, return time, departure time and required departure charge. Use real operational records when available and label assumptions when vehicles have not yet arrived.

A fleet charging assessment should combine this operational brief with electrical supply and site constraints. The ARENA-hosted report cited below illustrates the breadth of infrastructure planning at another organisation’s depot; it is not a Solar Battery Australia project or a specification for your site.

A hypothetical first-pass calculation

Assume six vehicles each require 40 kWh delivered to the vehicle battery after a shift. Total energy is 240 kWh. If all have an eight-hour charging window, the arithmetic average is 30 kW delivered across the fleet: 240 ÷ 8. Grid energy and power would be higher after charging losses, and real arrival times and charging limits may prevent even distribution.

Average power is not a final supply requirement

If all six vehicles instead attempt 20 kW together, their combined demand is 120 kW before other depot loads. Managed charging may spread the work, but only if departure targets remain achievable. Model the busiest overlap and late-return cases, not just the average night. Confirm the vehicle’s charging curve and operational constraints with its supplier.

Combine charging with the existing site load

The commercial load-profile guide explains why interval data and opening hours matter. Add charging to that baseline rather than treating the entire supply as spare. The demand-charge guide explains why a short coincident peak can affect a tariff differently from total energy.

Solar may be useful when vehicles are present during generation. Overnight dwell alone does not create daytime charging opportunity. Use the solar-surplus charging explanation to distinguish opportunistic charging from a departure-critical requirement.

Stage infrastructure without assuming future demand

• Document today’s vehicles and a separate, dated growth scenario.
• Assess network capacity and lead-time dependencies before promising vehicle rollout dates.
• Plan cable routes, boards, civil work, traffic movement and safe equipment access.
• Define charger control, communications, billing and software ownership.
• Test failure cases: unavailable charger, internet outage and a missed charging session.
• Assign maintenance, support escalation and driver training responsibilities.

A staged plan should state which works are required now, which provisions preserve future options and which depend on later approvals. Do not assume a battery eliminates a network constraint or that software can always compensate for insufficient charging time. Use the project planning table alongside the broader commercial EV charging service to allocate these decisions.