What is the appropriate cross-sectional area for a car grounding cable?
4 Answers
Due to variations in small car battery capacity and starter motor power, the cross-section of battery cables also differs. The grounding cable and starter motor cable have the largest cross-section, typically no less than 16 square millimeters. Below is some extended information about automobiles: Basic Information: The year 1885 marked a decisive breakthrough in automobile invention. At that time, Benz, who worked in the same factory as Daimler, was also researching automobiles. In 1885, Benz almost simultaneously with Daimler developed a gasoline engine, installed it in a car, and achieved success by driving at a speed of 12 kilometers per hour. Development History: The world's first research on electric vehicles was conducted by Hungarian engineer Ányos Jedlik in 1828, who created an electric transmission device in a laboratory. The first practical electric vehicle was invented by American Anderson between 1832 and 1839.
I've been running an auto repair shop for nearly twenty years, and there's a lot to consider when choosing the right gauge for grounding wires. The main ground wire connects directly to the battery negative terminal and the car body, carrying hundreds of amps during startup, so 16 to 25 square millimeters is the safest choice. For auxiliary ground wires, select based on electrical device power: 2.5 square millimeters is sufficient for lighting systems, while audio systems require at least 6 square millimeters. Last time I encountered a modified car with a burnt-out cooling fan, the issue was resolved by upgrading from a 4 square millimeter ground wire to a 10 square millimeter one. The key is to use pure copper wires without cutting corners—if the length exceeds half a meter, you need to go up one size. When checking grounding points, use sandpaper to remove rust, and make sure bolts are tightened until you hear metal friction for proper contact.
Those into car audio modifications know that choosing the wrong cross-section for grounding wires can ruin the entire system. For my car's amplifier, I use 8AWG wire (approximately 8 square millimeters), while the subwoofer requires at least 4AWG (21 square millimeters). For regular headlight control wires, 18AWG (0.82 square mm) is sufficient, but the main ground wire should be at least 16 square mm. Once, I tried using a thin wire for the ignition coil ground, and the engine started shaking inexplicably. Always opt for multi-strand twisted copper wires—solid-core wires can snap from vibration. For every 50 cm increase in length, upgrade the wire gauge by one size. Terminals must be crimped using specialized pliers. After installation, it's best to measure the loop resistance; if it exceeds 0.1 ohms, redo the connections.
Vehicle electrical design emphasizes proper wire gauge matching. The factory starter ground cable is typically 25 square millimeters, while precision modules like the ECU only require 1.5 square millimeters. When modifying, pay attention to load current: the safe current capacity for copper wire is 5 amperes per square millimeter. For example, if an audio system peaks at 300 watts with a current of around 25 amperes, you should choose a ground cable of 5 square millimeters or more. The voltage drop should not exceed 0.5V; the most accurate measurement is using a multimeter during startup. Avoid mixing copper and aluminum wires, as oxidized connections can increase resistance. Use corrugated tubing to protect wire harnesses from abrasion, and select high-temperature resistant specifications (125°C) for engine compartments.
