MCS — Megawatt Charging System for heavy road transport

The 722-ev-charging guide and the guide on charging hubs and dynamic load balancing cover charging installations within the power range of passenger cars and vans — up to a few hundred kW per charge point. This article covers MCS (Megawatt Charging System): a charging standard developed by CharIN (Charging Interface Initiative) for heavy road transport (electric trucks, coaches), which is an entire order of magnitude above existing CCS charging infrastructure in terms of power.

Power range: a different order of magnitude than CCS

A regular CCS Combo 2 fast charger for passenger cars typically delivers up to roughly 350-500 kW, at voltages up to about 1000V DC and currents up to roughly 500A.
MCS is specified for power levels up to roughly 3.75 MW per connection, at voltages up to 1250V DC and currents up to 3000A — well beyond what a conventional, air-cooled charging cable and connector can handle.

Communication standard: the same protocol family as V2G

Communication between vehicle and charge point for MCS uses the same protocol family as bidirectional charging for passenger cars — ISO 15118-20 — supplemented with specific MCS connector requirements (among others via IEC 61851-23-3 and SAE J3271). See the guide on V2G and bidirectional charging for the background of that protocol for passenger cars.

Why liquid cooling is a necessity here, not an option

For a 350 kW CCS charger for passenger cars, a liquid-cooled charging cable is a way to make the cable thinner and lighter than an air-cooled cable would be at the same current — practically desirable, but not strictly necessary. At MCS current levels (up to 3000A), an air-cooled cable with a manageable diameter and weight is no longer feasible: the conductor cross-section that would be needed to carry that current without active cooling would make the cable too stiff and too heavy to still be handled manually. Liquid-cooled cables and connectors are therefore a fundamental part of the MCS design, not a comfort upgrade.

Protection aspects at DC level

At this combination of high DC voltage and high DC current, the same principal considerations apply as for other high-power DC systems in the installation:

DC arc-fault detection: a DC arc, unlike an AC arc, has no natural zero crossing and is therefore harder to self-extinguish (see the guide on DC arc-fault detection in PV strings for the same underlying physical principle, applied to a different DC application) — at MCS power levels, reliable DC arc detection is an essential part of the protection.
DC protective devices: switching and protective devices for this voltage and current range must be specifically tested and rated for DC (see the [guide on DC protection and cable sizing for BESS](/guides/nen-1010/bess-gelijkstroom-dc-beveiliging-kabeldimensionering) for comparable considerations for stationary DC battery systems) — an AC protective device is not automatically suitable for DC interruption at these current levels.

Grid connection: from a single charge point to a grid-congestion question

A single MCS connection at full power already requires a connection capacity comparable to a mid-sized industrial site. A truck depot with multiple MCS charge points used (partly) simultaneously quickly reaches an aggregate power of tens of MW — a scale that directly touches the grid-congestion issue that also affects large-consumer connections elsewhere. As described in that guide, a combination of dynamic load balancing (see the charging hubs guide) and on-site battery storage for peak shaving is often necessary to realise an MCS depot within a feasible connection capacity.

Note: at the time of writing, MCS is an emerging technology for which no dedicated NEN 1010 chapter yet exists — comparable to how §722 was once added specifically for EV charging. Until such a chapter exists, the installation falls under the general requirements for overload and short-circuit protection (§433/§434) and switching devices (§537), supplemented with the manufacturer and CharIN specifications for the MCS equipment itself.

Practical relevance

When designing charging infrastructure for heavy transport, it is not sufficient to simply scale up experience from regular EV charge points to MCS power levels — both the physical implementation (liquid cooling, DC protection) and the grid connection (aggregate power, grid congestion) require an approach closer to industrial or utility-scale infrastructure than to regular charging hubs.

Common mistakes

Directly scaling passenger-car charging infrastructure up to MCS power levels without accounting for the physical limits of air-cooled cables and the resulting need for liquid cooling.
Applying AC-world DC protective devices to an MCS installation — DC interruption at these current levels requires equipment specifically tested for DC.
Underestimating the grid connection of an MCS depot by looking only at the power of a single charge point instead of the simultaneous aggregate power of the entire depot.