Check the leakage current of the car and whether the multimeter is in the AC or DC gear
Check the leakage current of the car and place it in the DC current. First, disconnect the main isolation switch of the user's power inlet, and turn off all electrical loads of the user, such as unplugging the refrigerator plug and disconnecting the water pump switch. Place the digital multimeter in the 200M range of the Ohm range, with one probe placed on one of the two output wires on the load side, and the other probe touching the wall, preferably the grounding wire or temporary grounding wire.
After the number displayed on the multimeter stabilizes, the reading is the insulation resistance value of the main line. If the insulation resistance value is less than 0.5 megohms, it is a problem with the main line. If the insulation resistance is above 0.5 megohms, it can be ruled out that there is a problem with the main line.
Extended Information:
In addition to battery leakage, the circuit also consumes some current. There is no absolute insulation system, and many loads are not directly disconnected when the key switch is turned off, such as anti-theft devices that consume some current. Traditional cars generally have a dark current of around 30 milliamperes, as many on-board appliances are installed, the static current may be relatively high, but it cannot exceed 50 milliamperes.
Because car batteries are generally around 60 ampere hours, 60 * 1000 ÷ 50=1200 hours, 1200 ÷ 24=50 days, that is to say, under a leakage current of 50 milliamperes, a single battery theoretically takes 50 days to fully discharge all its electricity. In fact, it is impossible to fully discharge it, and the car cannot be started after being stored for a month.
Determine if the dark current of the entire vehicle is greater than 50 milliamperes, such as 80 milliamperes, 80-50=30 milliamperes, 30 * 12/1000=0.36 watts. You can roughly determine which load's static power is closer to this, such as the static current of the navigation instrument. To check if the power supply of the navigation instrument is not turned off.
If you are unable to find any leakage points at the moment, you can unplug the fuses, relays, or disconnect the ground wires of some loads one by one to see where the leakage current displayed by the multimeter suddenly drops, indicating that the problem lies in this circuit. Then, disconnect from this circuit separately and continue to narrow the range until you find a suitable leakage point.
