Parasitic drain test – battery

The purpose of this test is to evaluate the level of parasitic current draw from the battery during a vehicle's shutdown phase and sleep periods.

Connection guidance

Connection for diagnostic work will vary dependent on application.

Technicians should whenever possible gain access to the test circuit without damage to seals and insulation. If this is not possible then make sure appropriate repairs are completed.

Parasitic drain test pre-requisites;

Vehicle must achieve full electrical shut down;

  • All openings to register as closed with Body Control Module (BCM)
  • Alarm activated
  • Remote keys out of range
  • Aftermarket accessories set as customers usual use

Ensure the test equipment is able to function for an extended time period e.g. current clamp battery condition, scope and pc power supply.

How to perform the test

  1. Ensure the vehicle is able to achieve full electrical shut down with PicoScope connected. (see connection guidance).
  2. Ensure the ignition and all accessories are turned off.
  3. Connect PicoScope channel A across the battery terminals.
  4. Connect the low amp TA234 current clamp to PicoScope channel B and select the 20 A scale.
  5. Wait around 10 minutes for the current clamp to acclimatise to test conditions (temperature), then connect around the battery earth lead.
  6. Minimise the help page and with the example waveform on your screen PicoScope has already selected suitable scales for you to capture a waveform.
  7. Start the scope to see live data.
  8. Some vehicles may take around 45 minutes to completely close down all electrical systems. (You may need to test for longer periods, e.g. Over-night to acquire sufficient test data).
  9. With your live waveform on screen stop the scope.
  10. Apply a Lowpass Filter to clean the channel B waveform.
  11. Use the Waveform Buffer, Zoom and Measuring tools to examine your waveform.

Example waveforms

Waveform notes

All values included in the example waveforms are typical and not specific to all vehicle types.

  1. Battery voltage.
  2. Current draw from the battery during the shutdown period of the vehicle networks and accessories.
  3. A reduction in current draw from the battery as the networks begin to sleep.
  4. The parasitic current draw from the battery as it settles at 40 mA for over 21 minutes (sleep mode).
  5. The networks waking up in response to the activation of the key fob/set.

Further guidance

Refer to vehicle technical data for specific test conditions and results.

The battery voltage should remain stable and between 12.4 V and 12.8 V throughout the test. The current draw from the battery during the shutdown period of the vehicle networks and accessories is 228 mA for over 6 minutes. The shutdown periods can range from 30 minutes to 2 hours (depending on manufacturer). The current draw will also vary depending on network and system activity. You can clearly see a reduction in current draw from the battery as the networks begin to sleep and the parasitic current draw from the battery as it settles at 40 mA for over 21 minutes (sleep mode). The target parasitic drain is < 80 mA and stable throughout. It is clear on the waveform when the networks wake up, responding to the activation of the key fob/set. The vehicle is now unlocked and the networks are awake.

You can read more about Parasitic drain testing in the online training section on our website.


This help topic is subject to changes without notification. The information within is carefully checked and considered to be correct. This information is an example of our investigations and findings and is not a definitive procedure. Pico Technology accepts no responsibility for inaccuracies. Each vehicle may be different and require unique test settings.

Suitable accessories

  • 30 A (low amps) current clamp


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Guided test: Parasitic drain test - battery