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Parasitic Battery Draw Test

A dead battery causing your car to not start is never fun. You recharge the battery or replace it and the vehicle’s alternator is functioning properly, but the car doesn’t start again the next day. The battery is dead again! This is called a parasitic draw or an unintended battery drain. Ever accidentally leave a dome light on and kill the battery? That’s just one example. Check out the video below to learn how to perform parasitic draw testing.

Parasitic Battery Drain test Procedure

  1. Ensure battery is fully charged and the vehicle charging system is operating properly – Watch
  2. Prep vehicle for test by opening doors, trunk, hood, etc and trip the latches - Watch
  3. Verify parasitic draw is present by placing multimeter set to 10 amperage setting in between the negative battery terminal and the negative battery cable. This forces any current being drawn from the battery through the multimeter. - Watch

Tip – Most multimeters can only handle 10 amps of curr ent draw. Be sure to not turn on any vehicle accessories, lighting, or start the car with the meter attached between the negative battery terminal and negative battery cable.

  1. Allow the vehicles systems to enter sleep mode. This can take anywhere from two minutes to over one hour on some vehicles
  2. Check amperage reading on multimeter - Watch

Tip – 0.050 amps or 50 milliamps and under is general rule

  1. Using a multimeter set to millivolts begin looking for voltage across the fuses. Anything greater than 0.000 is an indication of current flow - Watch
  2. Use wiring schematic to determine what’s in the circuit that ties to fuse identified above - Watch
  3. Fix or repair faulty component that is causing unintended amperage draw
  4. Re-inspect parasitic draw value ensuring its under 50 mA - Watch