Why does the charging cable get warm?

Why does a charging cable get warm? What is normal and what is not

When a modern electric vehicle (EV) connects to a charging station, enormous amounts of energy flow through it. If you then touch the connector and notice the charging cable getting warm, you may well wonder: is that safe?

Let us put your mind at ease straight away: the answer is almost always yes, because warmth is not necessarily a warning sign. Often, it is simply physics at work. If you want to know more about what happens during charging, we explain it here!

The physics behind heat during charging

High-power charging (HPC) pushes enormous amounts of electricity into the battery in a very short time. Wherever electric current flows through copper cables, natural electrical resistance occurs. Some of the energy inevitably turns into heat. So it is entirely normal for a cable to get warm during charging.

Three factors in particular affect the temperature:

• Charging power: the more kilowatts that flow through the cable, the warmer the system becomes.
• Outside temperatures: In the height of summer, all components start at a significantly higher baseline temperature.
• Duration of peak load: When batteries are charged at maximum power for an extended period, temperatures remain high.

To control this heat buildup, cables at HPC stations are generally liquid-cooled. The intelligent cooling system keeps temperatures stable and the charging cable warm but always safe to handle.

Smart technology for safe EV charging

One aspect often overlooked in ultra-fast charging is the highly complex data communication that takes place during the session. The station does not simply force electricity into the vehicle; instead, the car's systems set the pace.

The electric vehicle's battery management system (BMS) constantly monitors the condition of the battery cells. It communicates with the charging station in real time and requests precisely the amount of current the system can safely handle at that moment. If the battery or cable becomes too warm, the technology intervenes immediately:

The vehicle automatically reduces the requested charging power to allow the components to cool down. That is why charging power usually falls significantly once the battery reaches 80% charge. This intelligent control also ensures that physical limits are never exceeded and charging remains completely safe.

=> Looking for tips on charging? Head this way!

Warning signs: When heat becomes a problem

Despite all the safety mechanisms and the low likelihood of danger, there is a clear line between a safe operating temperature and critical overheating. Watch for the following signs, as they may point to a defect:

1. Too hot to handle: The connector or cable gets so hot that you can no longer comfortably hold it in your bare hand.
2. Visible defects: Melted plastic, a deformed connector housing or a distinct smell of burning indicate damaged contacts.
3. Sudden interruption of charging: If the sensors detect critical heat buildup that cannot be controlled by reducing power, the system stops charging immediately for safety reasons.

If you encounter such a situation, report it to the charging station operator and have your vehicle inspected by qualified personnel!

A modern charging station for your site with JOLT

To minimise the risk of heat-related problems or damage from the outset, we use smart hardware. MerlinOne puts safety first with retractable cables. This prevents charging cables from lying on the ground and being driven over, which can cause invisible damage that later leads to dangerous overheating. Our charging stations have integrated battery storage, allowing a seamless connection to the standard low-voltage grid without expensive, time-consuming grid upgrades.

=> Find our charging locations here!

By the way, as a site partner you benefit from a complete worry-free package: We plan, finance and operate premium charging equipment at your location. You provide the space; we take care of the rest.

Prepare for the future of electric mobility. Contact us now to upgrade your site with forward-looking, safe charging infrastructure!