How Can I Test My Car Battery for a Trickle Drain?

Written by david sandoval
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How Can I Test My Car Battery for a Trickle Drain?
It is important to isolate the parasitic device within the electrical system. Test each circuit branch at the fuse box. (series object on white: safety fuse image by Aleksandr Ugorenkov from

Automobile batteries provide a grounding source for an automobile, as well as providing start-up power for the engine and ignition electronics. Typically, when an automobile is switched off, only a negligible draw of electrical current should exist.

If an automobile continues to draw excessive electrical current when the engine is switched off, a parasitic drain on the battery is the problem, which must be found.

Skill level:
Moderately Challenging

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Things you need

  • Digital multimeter
  • Slip-joint pliers
  • Adjustable wrench
  • Fuse puller tool

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  1. 1

    Hold the positive battery terminal retaining bolt with the slip-joint pliers. Using the adjustable wrench, loosen the positive battery terminal retaining nut. Disconnect the positive battery cable from the positive battery post.

  2. 2

    Turn on the multimeter, and set it to the "DC Amps" setting. Place one of the probes on the positive battery post, and place the other probe on the battery cable terminal. Read the multimeter display; if the electrical current measurement is more than 50 ma, there is a parasitic drain on the battery.

    How Can I Test My Car Battery for a Trickle Drain?
    Measure the output current with a multimeter to determine whether the battery is being drained. (Digital Multimeter image by TekinT from
  3. 3

    Install the battery cable on the positive battery terminal, and tighten the retaining nut until the terminal is snug on the battery post. Open the automobile fuse box.

  4. 4

    Pull the first fuse out of the fuse holder. Place one probe on one of the fuse holder connectors, and place the other probe on the opposite fuse holder connector. Read the multimeter display. If the electrical current reading is less than 50 ma, replace the fuse and repeat this step on the other fused circuits until the battery draining device is found.

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