35cm × 35cm, 350 Kilowatts: The Satellite Terminal at the Heart of Fleet Charging

When a fleet depot commits to electrification at scale, the question of where the charging equipment goes becomes as important as how much power it delivers. A 50-bay bus garage cannot accommodate 50 large power cabinets. The physics of power distribution demands hardware at bay level; the economics and operational constraints of a working depot demand that it takes as little space as possible.

The Neutron DC Satellite Terminal is the hardware that resolves this tension. It stands approximately 1.5 metres tall, occupies just 35cm × 35cm of floor space, and serves as the power distribution node for a cluster of charging bays. Each connector port can deliver up to 600kW with the liquid-cooled cable upgrade. The same terminal supports any combination of Neutron's three connector types: side-mount, drop-down (NSNF0014DDC), and in-ground (NSNF0015GRC).

What the Satellite Terminal Actually Does

The Satellite Terminal is not a charger in the conventional sense. It contains no AC-to-DC conversion. It does not connect to the mains supply. Instead, it receives high-voltage DC from the Master Unit via a single DC bus cable and distributes that power to the connector ports it serves, under instruction from the Master Unit's power management system.

At each charging event, the vehicle requests a charge. The Satellite Terminal reports the request to the Master Unit, which allocates power from its total available capacity based on current demand across all terminals and all bays. If five bays are active simultaneously and two more vehicles connect, the Master Unit re-optimises the allocation in real time. No power is wasted on idle bays. No vehicle waits longer than the system's overall capacity requires.

The terminal also handles metering, communications (CAN bus and Ethernet), and the display interface that drivers and ground crew interact with. In the event of a fault at the terminal or connector level, isolation is at terminal level only: the rest of the system continues operating unaffected.

A Neutron Satellite Terminal in service at a London bus depot. The compact white column serves multiple bays; the Neutron Master Unit is visible further back in the depot.

Three Connector Types, One Terminal

One of the less obvious advantages of the Satellite Terminal architecture is connector flexibility. A single terminal can simultaneously serve bays fitted with different connector types, because the terminal is the hub from which any of the three Neutron connector types hang:

• Side-mount connectors: wall or post-mounted, the most common arrangement for new-build depots with clear wall runs.
• Drop-Down connectors (NSNF0014DDC): overhead gantry-mounted for covered depots where floor space is the constraint.
• In-Ground connectors (NSNF0015GRC): flush-mounted in the tarmac for zero above-ground footprint in open yards.

This means a single Satellite Terminal serving a mixed bay layout, part covered, part open yard, can simultaneously support an overhead connector on one bay and an in-ground connector on an adjacent bay. Operators are not locked into a single installation strategy at the point of deployment: the terminal hardware remains the same regardless of the connector type at the vehicle end.

Safety by Architecture

Conventional DC chargers present live high-voltage connections at vehicle level: the charger cabinet carries the full DC bus, and the cable between cabinet and vehicle inlet operates at 400-1000V DC depending on platform. This requires permanent safety exclusion zones around each cabinet and means that maintenance at bay level always involves isolation procedures.

In the Satellite Terminal architecture, there is no high-voltage equipment at bay level. The terminal's connector ports present less than 36V DC on their external surfaces until a handshake with a connected vehicle has been verified and the power path opened at the Master Unit. A technician can work at the terminal or disconnect a cable at bay level without isolating the system or the Master Unit. Only the specific connector path is de-energised, and only for the duration of that intervention.

The Full System: Master, Satellite, and Connectors

A typical 50-bay bus depot might deploy two 480kW Master Units (960kW total conversion capacity), eight to ten Satellite Terminals distributed across the yard, and a mix of connector types matched to the specific characteristics of each bay cluster. The total cabling between components is dramatically less than an equivalent installation of 50 individual DC chargers, because the high-current DC bus from the Master runs to each Satellite Terminal via a single cable route, not 50 separate conduit runs from the grid connection point.

For a detailed explanation of the Master-Terminal architecture and how it reduces civil works costs by up to 30%, see our article on scaling fleet depot charging to 4MW.

Liquid Cooling and High-Power Delivery

Standard Satellite Terminal connectors operate at up to 250kW per port on air-cooled cables. The liquid-cooled upgrade increases this to 600kW per connector by circulating coolant through the cable core, removing the heat generated at full rated current and allowing a physically lighter and more flexible cable to carry the higher amperage.

The cooling circuit is managed entirely by the Satellite Terminal. There is no separate cooling infrastructure required at the connector end. For depots deploying high-capacity buses with 400kWh batteries or larger, the liquid-cooled option significantly reduces overnight charging dwell time per vehicle.

HV Direct and the MCS Upgrade Path

The Satellite Terminal is designed with the next vehicle generation in mind. As 800V battery platforms enter the UK bus and coach market, and as MCS (Megawatt Charging System) becomes the standard for high-capacity charging events, the terminal architecture supports the transition without requiring replacement of the bay-level infrastructure.

Neutron's HV Direct capability extends the Master Unit's output voltage range to support 800V operation. The Satellite Terminal passes this higher voltage to the connector, where an updated connector head (CCS2 to MCS) is the only hardware change at bay level. The terminal column, its mounting, the DC bus cable from the Master Unit, and the civil infrastructure all remain in place.