Parasitic drain test – battery

You will require a PicoScope to perform this test. A list of suitable accessories can be found at the bottom of this page.

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.

To obtain the correct parasitic drain values it is essential to make sure that the vehicle battery is serviceable and fully charged with all accessories switched off. The vehicle must be locked (security systems armed), and for keyless and Smart Entry System (SES) vehicles make sure that all keys are out of the detection range of the vehicle.

Note: additional accessories, which are not visible, may have been installed.

For example, location devices, data loggers, motion cameras, entertainment accessories, in-car chargers and additional anti-theft devices; all of which may consume current and contribute to parasitic drain levels.

Contact the vehicle owner for clarification on any of the above installations.

How to perform the test

 

Accessories

 

 

PicoScope settings

 

  • Channel A: ± 20 V
  • Channel B: ± 500 mA
  • Timebase: 200 s/div
  • Number of samples: 1 MS

 

Alternative current clamp:

TA018 20/60 A DC (low amps) current clamp – see Modification notes below.

  1. Prepare:
    1. Make sure that the current clamp has sufficient battery voltage for extended parasitic measurements. The internal battery voltage should be above 8 V to ensure stable readings during prolonged measurements.

    2. Switch on the current clamp and let it warm up internally while it acclimatizes to the workshop temperature (approximately 10 minutes)

    3. Make sure that all doors and windows are closed and that the vehicle battery remains accessible.
      • Where the vehicle battery is located inside the engine bay, make sure that the bonnet latch is closed and that the bonnet position switch is set to the closed position with the bonnet raised. Where the vehicle battery is located inside the luggage bay, make sure that the luggage door latch is closed and the luggage door position switch is set to the closed position with the luggage door open. (It is important that the body control system recognizes that these panels are closed in order to commence the shutdown of the vehicle networks.)

    4. Make sure that the ignition is switched off.
      • In the case of a vehicle with a keyless or SES, lock the vehicle with the key fob/set and place the keys out of range of the vehicle (two meters minimum distance between the vehicle key set and the vehicle). These vehicles have the ability to detect the presence of the keys in the area around the vehicle, preventing full shutdown of the network.

    5.  
  2. Connect the test lead to Channel A on the scope.

  3. Connect the coloured end of the test lead to the battery’s positive terminal and the black ground lead to the battery’s negative terminal.

  4. Connect the current clamp to Channel B.

  5. Run PicoScope Automotive by clicking the Go button or pressing the space bar on your keyboard.

  6. Zero the current clamp and connect it around the battery negative lead (note the orientation of the current clamp in relation to the current flow).

  7. Let the scope capture sufficient data to confirm the shutdown period and sleep mode of the vehicle (up to 45 minutes). Here, you will measure the parasitic current drain, looking for a target value of less than 80 mA after 45 minutes.

  8. Press the Stop button in PicoScope to stop the capture.

  9.  

Lowpass filtering

Lowpass filtering is incorporated into the PicoScope software and can be applied to any channel to remove high frequency noise and reveal the true signal level beneath.

A 1 Hz lowpass filter applied to any signal will reject all frequency signals above 1 Hz. Only signal values of 1 Hz and below will pass through and be displayed.

To activate/deactivate the lowpass filtering feature:

  1. Click on the channel options button.
  2. Check the Activate filtering checkbox.
  3. Select the level of lowpass filtering required (in this case 1 Hz).

Click anywhere on the scope grid to exit the channel options menu.

Modification notes


Alternatively, the TA018 20/60 A current clamp (small jaw) can be used on channel B. However, before you make any measurements with PicoScope, you need to make sure that the opening of the TA018 current clamp jaw is wide enough to connect around the battery negative cable. Where the diameter of the battery lead exceeds 8 mm, you will need to insert a 10 A fused jumper wire between the battery's negative terminal and the battery lead (see image).

In order to simulate the shutdown scenario of the vehicle it is essential that the battery negative terminal remains connected to the chassis via the fused jumper lead. If the battery lead is disconnected, the battery will reboot on-board computers preventing accurate and realistic parasitic drain results.

To avoid momentary disconnection of the battery (and excessive current draw), insert the fused jumper wire by following the procedure listed below:

  1. Slacken the negative battery lead clamp around the negative battery terminal and slowly raise the lead to expose the lower section of the negative battery terminal.
  2. Connect the fused jumper wire to the exposed section of the negative battery terminal and the negative battery lead clamp.
  3. With the fused jumper wire in place, the connection between the negative battery terminal and battery lead can be broken as the fused jumper wire will maintain the continuity of the vehicle ground to the battery negative terminal.
  4. Zero the TA018 current clamp with the push button on the clamp, and connect it around the fused jumper wire (note the orientation of the current clamp in relation to the current flow).

Note: Once the test is complete, re-establish a partial connection between the negative battery terminal and battery lead (as in Fig 2 above). Once partial connection is complete, remove the fused jumper wire, press the battery clamp down to seat it correctly, and tighten securely.

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.

Diagnosis

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.

Additional information

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

AT783-2

Disclaimer
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

  • 20 A / 60 A DC (low amps) current clamp

    £159.00

  • 30 A (low amps) current clamp

    £259.00

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Guided test: Parasitic drain test – battery