Check the leakage current of the car, whether the multimeter is placed in the AC gear or the DC gear
Check the leakage current of the car and put it in the DC current, first disconnect the main isolating switch of the user's power supply line, and turn off all the user's electrical loads, such as unplugging the refrigerator, disconnecting the water pump switch, etc. Put the gear of the digital multimeter on the 200M gear of the ohm gear, place one test lead on one of the two outlets on the load side, and the other test lead touch the wall, preferably the ground wire or a temporary ground wire .
After the number displayed on the multimeter is stable, the insulation resistance value of the main line is read. If the insulation resistance value is less than 0.5 megohm, then there is a problem with the main line. If the insulation resistance is above 0.5 megohm, it can be ruled out. It's a problem with the main line.
In addition to the leakage of the battery, the line will also consume some, there is no absolute insulation system, and many loads are not directly cut off when the key switch is turned off, such as the anti-theft device will consume some current. In a traditional car, the dark current is generally around 30mA. Because many on-board electrical appliances are installed, the quiescent current may be relatively large, but it cannot be higher than 50mA.
Because car batteries are generally about 60 ampere hours, 60*1000÷50=1200 hours, 1200÷24=50 days, that is to say, a battery, under the condition of 50 mA leakage current, theoretically takes 50 days to fully charge After discharging all the electricity, in fact, it is impossible to discharge all of them. Generally, the car cannot be started after one month.
Make sure that the dark current of the whole vehicle is greater than 50mA, for example, 80mA, 80-50=30mA, 30*12/1000=0.36W, you can roughly judge which load’s static power is closer to this, for example The quiescent current of the navigator is relatively close to this, and it is necessary to check whether the power of the navigator is not turned off.
If you can’t find where the leakage is, 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. Inside, and then from the inside of this circuit, disconnect them separately and continue to narrow the range until you find a suitable leakage point.
