Cable heating follows Joule's law, P = I²R. Heat rises with the square of current, not linearly, so doubling the current from 500 A to 1,000 A through the same conductor quadruples the heat dissipated in the copper core. MCS allows up to 3,000 A at 1,250 V (3.75 MW), which would mean 36 times the resistive heat of a 500 A cable of the same resistance. Simply adding copper does not scale: a passively cooled conductor big enough to carry megawatt currents would be too heavy and rigid for a driver to handle.
| Parameter | Uncooled CCS (~150 kW) | Liquid-cooled CCS (350 kW) | Liquid-cooled MCS (3.75 MW) |
|---|---|---|---|
| Rated current | ~200–250 A | ~500 A | Up to 3,000 A |
| Max voltage | ~1,000 V | ~1,000 V | 1,250 V |
| Relative I²R heat (same R) | ~0.2× | 1× | Up to 36× |
| Conductor design | Large solid cross-section, passive | Reduced cross-section around coolant conduits | Fine-strand bundles packed around high-flow conduits |
| Heat rejection | Convection to ambient | Pump and radiator/chiller | Dedicated chiller plus high-pressure pumps |
| Parasitic load | Negligible | Continuous, kW-scale | Continuous, multi-kW per dispenser |
MCS cables solve this with active cooling. Manufacturers pack ultra-thin, highly flexible copper strands tightly around internal fluid conduits, so the coolant pulls heat directly from the conductor. A standalone chiller and high-pressure pump at each dispenser keep handle and jacket temperatures below about 60°C, and these systems must run whenever the charger is live or recovering from a session.
For depot operators, that thermal plant is a permanent line item. Every kilowatt-hour drawn by chillers and pumps is bought from the grid but never reaches a truck battery. This parasitic overhead inflates the total cost of ownership (TCO) per delivered kilowatt-hour, and it grows with ambient temperature and duty cycle. Fleet directors and grid specifiers should therefore model chiller loads, standby cooling and seasonal efficiency alongside headline MCS power ratings when sizing grid connections and pricing depot energy.