Look closely at an ultra-fast charger and you may notice its cable is surprisingly slim for the power it carries. That is because the cable is cooled from the inside by a circulating liquid. Without it, high-power charging would be impractical.
The problem: heat
Charging power is voltage multiplied by current. To deliver more power, chargers push more current through the cable, and more current means more heat. Heat rises with the square of the current, so doubling the current produces about four times the heat in the same cable.
The obvious fix doesn't work
A thicker copper cable carries more current with less heat. But at ultra-fast power levels, a passively cooled cable would become so thick and heavy that many people could not lift it or plug it in comfortably, and it would be hard to manage on a public charger.
How liquid cooling works
- A coolant flows through channels inside the cable and around the connector contacts.
- It carries heat back to a cooling unit in the charger, where a radiator and fan release it.
- Temperature sensors in the connector let the charger reduce power if anything gets too hot.
The result is a cable thin and light enough to handle, carrying far more current than an uncooled cable of the same size.
When you need it
- Most AC and moderate DC chargers use normal, uncooled cables.
- Ultra-fast DC chargers for newer cars that accept very high power usually need liquid-cooled cables.
- Heavy vehicles and megawatt charging rely on liquid cooling to deliver very high currents. See megawatt charging explained.
What it means for operators
- Maintenance: coolant level, pumps, filters and leaks need regular checks.
- Cable care: cables are expensive to replace, so holsters, cable management and bollards matter.
- Monitoring: cooling faults should raise alerts before drivers notice slower charging.
- Spares: keep replacement cables available, or agree fast supply with the manufacturer.
EVee Buddy includes cooling-system checks in preventive maintenance for every high-power site we operate.