Fleet Depot Charging Systems
Fleet depot charging systems define how mixed commercial fleets receive energy at home base. This page builds on the EV fleet charging overview and focuses specifically on how charging works inside fleet energy depots for robotaxis, delivery fleets, freight, industrial equipment, UAVs, and humanoid robots.
Unlike public fast charging or ad hoc site installs, depot charging is planned, repeatable, and tightly integrated with routing, duty cycles, and energy costs. The goal is not just to charge each vehicle, but to sustain predictable throughput for the entire fleet.
Depots in the Fleet Charging Landscape
Depots sit alongside home, workplace, corridor, and public fast charging, but play a distinct role for commercial EVs.
- Home and workplace charging — useful for light-duty and some service fleets, but limited for high-duty cycles.
- Public DC fast charging — critical for coverage and redundancy, but expensive and hard to control for fleets.
- En-route and corridor charging — complements depots for long-haul freight and regional distribution.
- Fleet energy depots — primary energy node for most commercial fleets, where charging is scheduled and optimized.
For high-duty fleets, depot charging becomes the anchor, and other modes act as buffers or exceptions.
Charging Levels/Modes at Depots
Commercial depots support multiple charging modes, tuned to the EV fleet mix and duty cycles. Most sites evolve from simple AC overnight charging to mixed DC and megawatt-class systems as fleets scale.
| Mode | Power Range | Best For | Notes |
|---|---|---|---|
| Depot AC (Level 2) | 11–22 kW | Light-duty support vehicles, pool cars, some delivery vans | Overnight or long dwell; lowest hardware cost and grid impact. |
| DC fast (Level 3) | 50–350 kW | Delivery vans, box trucks, shuttles, buses, robotaxis | Core workhorse for MD depots; supports shift changes and opportunity top-ups. |
| Megawatt-class (MCS) | 750 kW to 1.2+ MW | Class 7–8 tractors, heavy industrial mobile assets | Enables fast turn for long-haul and high-duty HD fleets; drives MV and transformer sizing. |
| Battery swap | Varies | UAV fleets, eVTOL prototypes, specialized logistics | Moves energy handling off-vehicle; requires tight pack standardization and logistics. |
| Robotic charging | 22–350 kW (LD/MD), 350 kW–1 MW (HD) | Robotaxis, AV delivery, automated yards, humanoid corridors | Automates plug-in; requires precise docking, sensing, and safety envelopes. |
Mixed voltage and multi-sector depots
Most depots eventually support assets on different voltage classes. Planning for heterogeneous fleets up front avoids stranded chargers and rework.
| Voltage Class | Typical Assets | Planning Notes |
|---|---|---|
| 400 V | Legacy LD EVs, some MD vehicles, many robotics platforms | Good fit for AC and lower-power DC clusters; suitable for support and early fleets. |
| 800 V | Next-generation MD/HD trucks, high-performance platforms | Enables higher sustained DC power; reduces dwell but increases hardware and insulation demands. |
| MCS-class HV | Class 7–8 tractors, heavy campus vehicles | Requires HV cabinets, liquid-cooled cables, and careful thermal design around pedestals. |
Depot charging layouts
Inside the yard, charger placement and traffic flow have as much impact on throughput as nameplate power. Common depot charging layouts include:
- Linear rows — vehicles nose-in or back-in to fixed pedestals along fences or walls; simple cabling and wayfinding.
- Island chargers — chargers in the center of bays, allowing access from both sides and supporting mixed fleet sizes.
- Pull-through lanes — essential for tractors and trailers; reduce complex maneuvers and congestion.
- Dedicated HD alleys — separate lanes for MCS or high-power DC to isolate heavy vehicles and longer dwell.
- Robotics corridors — dense rows of low-power points for humanoids and AMRs, often indoors and tied closely to compute rooms.
Charging topologies must align with arrival patterns, yard constraints, and safety rules, not just peak kW requirements.
Fleet segments and duty cycles
Duty cycles drive both power level and dwell-time strategies. Depots with mixed fleets typically segment parking and charger types by use case.
| Fleet Type | Typical Dwell Window | Charging Strategy |
|---|---|---|
| Robotaxis and ridehail | Short, frequent returns | Dense DC arrays; frequent top-ups; high charger utilization during peaks. |
| Urban and regional delivery | Overnight or clear shift breaks | Mix of AC and DC; predictable kWh per shift; strong fit for BESS load shaping. |
| Freight tractors | Mid-route and terminal dwell | MCS uplift at depots and corridor sites; turn-time targets dominate design. |
| Industrial yard equipment | Staging and shift overlaps | Moderate peak power, high concurrency; integration with plant loads and MV backbones. |
| UAVs and eVTOL | Rapid, high-intensity cycles | Pad-based charging or swap; power density per square meter is the main constraint. |
| Humanoids and AMRs | Continuous micro-charging | Low per-point power but very high density; charging tightly coupled to compute and workflow. |
Autonomous/robotic flee charging design
As fleets move toward autonomy, depots transition from driver-plugged charging to autonomous docking and robotic connectors. This changes both hardware and yard design.
- Automated parking and staging — vehicles navigate to assigned bays without drivers, relying on mapped lanes and fixed infrastructure.
- Robotic connectors — arms, underbody couplers, or movable pedestals align and connect without human intervention.
- Sensing and guidance — cameras, depth sensors, fiducial markers, and V2X support precise alignment and safety margins.
- Humanoid and AMR corridors — high-density, low-power docks integrated with local compute rooms for logs and OTA.
- Safety envelopes — clearly defined mixed zones where humans, vehicles, and robots coexist with speed and access limits.
In mature deployments, autonomous and robotic charging becomes a core design assumption rather than an optional upgrade.
Charger-to-Vehicle Ratios
Right-sizing charger counts is a balance between capital spending, utilization, uptime targets, and route design. Exact ratios are fleet-specific, but patterns are emerging.
- Robotaxi depots — relatively low vehicles per DC charger; availability drives revenue and uptime SLAs.
- Delivery depots — higher vehicles per charger; predictable windows allow smart queuing and load shaping.
- Freight hubs — MCS ratios driven by corridor schedules and turn-time, not just fleet size.
- Industrial yards — concurrency across shifts dominates; moderate kW, many connectors.
- Robotics depots — extremely high connector counts with low power per point; floor space, not kW, becomes limiting.
These ratios should be revisited as duty cycles, routes, and technology (such as autonomy and higher-voltage platforms) evolve.
Integration with depot energy and power
Depot charging systems cannot be designed in isolation. Charger placement, power levels, and concurrency assumptions directly shape transformer sizes, switchgear, BESS requirements, and tariff exposure.
- Peak power envelopes from charging plans inform MV interconnect and transformer banks.
- Load shifting via BESS depends on how much charging can be flexed in time without breaking duty cycles.
- Tariff structures reward depots that coordinate charging modes with time-of-use and demand limits.
- Future autonomy and corridor expansion should be treated as design inputs, not surprises.
