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Parasitic battery drain test

Parasitic battery drain test— How to

Test for Parasitic battery drain

There are two ways to test for a parasitic battery drain; current draw and voltage drop. Both methods require a digital multimeter. You can perform a current drain test with just your multimeter by connecting it in series with the negative battery cable. There’s a major drawback to this procedure though; the multimeter fuse is only 10-amps and can blow if you exceed that current draw. So you must exercise caution that you don’t operate any electrical accessories while testing with this method. To avoid the fuse issue, most shops use an inductive amp-clamp (more on that later).

The other method of testing for parasitic battery drain is to conduct voltage drop tests on each fuse. The fuse with the highest voltage drop will most likely be the circuit that’s causing the parasitic battery drain.

Test for parasitic battery drain using just a multimeter

series connection for parasitic battery current draw test

    1. Disconnect the negative battery cable
    2. Set multimeter to lowest AMP setting
    3. Move one lead to the AMP socket on your meter
    4. Connect the other lead to the COM socket on your meter
    5. Connect one lead to the battery NEGATIVE post
    6. Connect the other lead to the negative battery terminal
    7. With the key out of the ignition, let the vehicle sit for 15-45-mins to allow time for all computers to enter “sleep” mode.
    8. Note current draw. If the draw is above 50Ma, you have something drawing power.
    9. Remove one fuse at a time until the current draw falls below 50Ma. The fuse that causes the drop is the circuit causing the problem

Test for parasitic battery drain using a multimeter and amp-clamp

  1. Leave battery terminals connected to the battery.
  2. Connect the low current amp clamp to the negative battery cable.
  3. With the key out of the ignition, let the vehicle sit for 15-45-mins to allow time for all computers to enter “sleep” mode.
  4. Note current draw. If the draw is above 50Ma, you have something drawing power.
  5. Remove one fuse at a time until the current draw falls below 50Ma. The fuse that causes the drop in the circuit causing the problem

Test for parasitic battery drain using voltage drop with a multimeter

parasitic battery drain test

  1. Set your multimeter to the millivolt (mV) scale
  2. Connect the multimeter leads to the test point on each fuse
  3. If there is no current flowing through the fuse, the meter will read 0-volts
  4. If current is flowing through the fuse, you will get some reading.
  5. The fuses with the voltage are the circuits to check.

©, 2020 Rick Muscoplat

Posted on by Rick Muscoplat

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