How to Identify the Positive and Negative Terminals of a Car Battery?
2 Answers
The method to identify the positive and negative terminals of a car battery is as follows: You can determine the polarity based on the symbols marked on the battery. Generally, the positive terminal is marked with a '+' symbol, while the negative terminal is marked with a '-' symbol. When the polarity markings on the battery are unclear or faded, you can identify the terminals by their color. Typically, a red terminal indicates the positive pole, and a blue terminal indicates the negative pole. Additional information: A car battery is a type of battery, also known as a storage battery, which works by converting chemical energy into electrical energy. The commonly referred-to car battery is a lead-acid battery, which mainly uses lead and its oxides as electrodes and a sulfuric acid solution as the electrolyte. There are various types, including lead-acid batteries, nickel-iron batteries, and nickel-cadmium batteries. In a lead-acid battery, the positive electrode is lead dioxide, the negative electrode is lead, and the electrolyte is a dilute sulfuric acid solution. During discharge (use), the positive and negative electrodes react with sulfuric acid to form lead sulfate. When the concentration of the sulfuric acid solution drops to a certain level, the battery must be recharged. Using an external power source for charging can restore the electrodes and electrolyte to their original state, allowing the battery to be used again after charging.
I've always been quite interested in car maintenance, so I frequently check the battery terminals. Identifying the positive and negative terminals is actually quite simple: the positive terminal usually has a red protective cover marked with a plus sign, while the negative terminal is black with a minus sign. If the cover is missing or too corroded to see clearly, I can quickly confirm using a multimeter—when making contact, the reading from positive to positive should be close to 12 volts. If it shows a negative value when reversed, then I know I've got it wrong. When working on it, I always disconnect the negative terminal first to avoid short circuits and fires. For routine maintenance, I check the terminals monthly for corrosion. Simply wiping them clean with a cloth or giving them a light brush can extend the battery's life, especially in cold winter weather when problems are more likely to occur. Remember to turn off the engine before starting, and avoid wearing metal jewelry—safety first! By the way, if the car's electrical system has been modified, the terminal colors might have changed. In such cases, double-checking with a multimeter is more reliable.
