What is the normal amount of car battery drain?
2 Answers
Car battery drain typically has a normal value of around 40mA, though this can vary depending on the vehicle model. Some high-end cars may experience up to 80mA. The reason for this dark current is that certain electrical components in the car need to maintain data memory functions continuously, and anti-theft sensors also require long-term power supply to ensure the car's alarm system remains operational. Car battery drain refers to the gradual discharge of the battery when the vehicle is parked, which can affect engine startup or cause electrical malfunctions. Causes of car battery drain include: 1. Short circuits or oxidation shedding of battery plates; 2. Ground faults caused by electronic components and circuits such as car electronics, wiring harnesses, sensors, controllers, and actuators.
I used to worry about whether my car would leak too much electricity and drain the battery if left unused for a long time. Later, I found out through research that a normal leakage current should be below 50 milliamperes to be considered safe, meaning the battery would only lose a tiny amount of charge over a month. If the leakage exceeds 80 milliamperes, you should be cautious, as it might be due to aftermarket modifications or loose wiring. Testing for leakage is actually quite simple—just use a multimeter set to the current measurement mode, disconnect the negative terminal of the battery after locking the car, and measure the current in series. Pay attention to whether any abnormal dashboard lights stay on after parking for extended periods. Once, my car's battery died prematurely because of an aftermarket dash cam that consumed power too quickly, forcing me to replace it. So, I recommend avoiding unnecessary modifications to prevent increased leakage.
