What causes the DC line to get hot?

What causes the DC line to get hot?

When using DC cable, if the outer sheath becomes noticeably hot and scorching to the touch, it is an obvious indication of abnormal current loss. The root causes mainly lie in six categories: overload of the load, overly thin wire core, poor wiring connection, local short circuit between positive and negative poles, aging of the wire, and abnormal power supply voltage. Even with mild overheating, the insulation sheath will accelerate aging, hardening and cracking. In severe cases, the outer sheath will melt, causing short circuits and fires, and even burning the adapter and the downstream electrical equipment.

First, when the load current exceeds the capacity limit of the wire, it is the most common cause of overheating. Each type of copper wire with a specific diameter has a rated safe current capacity. Thin wires can carry large currents, and according to Joule's law, they will continuously generate heat. Commonly available DC thin wires usually have a cross-sectional area of 0.15 to 0.2 square millimeters, with a safe current of approximately 0.5A. If the working current of the equipment exceeds 1A, the internal resistance of the wire will continuously consume electrical energy and convert it into heat. Many routers, cameras, and LED light strips have a nominal current that is relatively small. During startup, the impulse current doubles, and in long-distance environments, the heat generation further intensifies. Low-quality copper-clad aluminum wire has a much lower conductivity than pure copper. Under the same current, it generates more heat than the standard copper wire by a factor of two. In a short period of time, it feels hot to the touch. The outer sheath of DC wire materials showing obvious heat and being hot to the touch during use is an intuitive manifestation of abnormal current loss. The root causes lie in overloading of the load, overly thin wire core, poor soldering of connections, local short circuits between positive and negative poles, wire aging, and abnormal power supply voltage. In mild cases, it accelerates the aging, hardening, and cracking of the insulation sheath. In severe cases, it melts the outer sheath, causes short circuits, and catches fire. It also burns the adapter and the downstream electrical equipment.

Secondly, an excessively long wire causes a significant increase in voltage drop and a passive increase in current. As mentioned earlier, when a DC wire is extended, the total resistance of the wire increases, resulting in the end devices not receiving sufficient voltage. The load will be passively forced to increase its input current to maintain operation, and the increase in current will simultaneously intensify the wire heating. For wires of the same specification, when used at room temperature within 1 meter, if the length is extended to 8 to 10 meters, there is a high probability of significant temperature increase. The finer the wire, the more prominent the heating phenomenon becomes.

Third, poor connection, loose solder joints, and localized high temperatures. The internal wiring of the DC plug is disconnected, the wires are wound and not soldered properly, the contact area of the contacts is small, and the contact resistance increases sharply. A large current passes through the solder joints, causing concentrated heating at the soldering points, and abnormal overheating occurs at the root of the plug. For the DC line with extended male-female plugs, multiple connection points are loose and oxidized, and each connection point generates additional power consumption. The heat accumulates layer by layer, causing the entire cable to heat up. The metal spring of the plug oxidizes and rusts to form an insulating layer, and the current only flows through sporadic points, which is also a typical cause of local overheating of the plug.
Fourth, hidden micro-short circuit hazards. The outer skin of the wire is damaged, and the positive and negative copper wires occasionally touch each other, resulting in intermittent short circuits. The current surges and heats up instantaneously during the short circuit. The damaged copper wire is close to the metal casing of the equipment and leaks electricity, continuously dissipating heat. When the long cable is stored with excessive bending and compression, the inner copper wires break and rub against each other, causing slight heating when unloaded and significant temperature rise when loaded.
Fifth, the aging of the wire and the accelerated heating due to the environment. In a long-term environment of high temperature, humidity, and cooking oil fumes, the copper wire oxidizes and forms copper rust, reducing the cross-sectional area of the metal conductor and increasing the resistance; the insulation layer shrinks and squeezes the inner wire core, causing the copper wire to deform under pressure, and the conductivity decreases. Old wires, after being repeatedly bent, half of the multi-strand copper wires break, and the remaining fine copper wires bear all the current, and they quickly overheat after being under load.

Sixth, the adapter malfunction causes abnormal output. The power adapter fails to stabilize the voltage, resulting in an excessively high output voltage. The actual power consumption of the equipment exceeds the limit, causing the overall power consumption to increase and the DC cable to overheat due to excessive load; the internal resistance of the adapter is abnormal, and the output current is uncontrollable. When a long cable is paired with a poor-quality power adapter, the entire system is prone to overheat.

Improvement plan: Immediately stop using the exposed wire material, replace it with a shorter line of the matching diameter according to the equipment's rated current; extend the power supply and use thick copper wire instead, remove multiple plug-in connectors, and fully seal the connections with solder; inspect the damaged and frayed wire materials and replace the faulty adapter.