How to check the hybrid battery on a Mercedes-Benz

One of the components that can fail and lead to no start condition on a Mercedes-Benz hybrid vehicle is the high voltage (HV) battery. 

In this short guide, we show how to check the resistance of the high voltage battery. This post is for information purposes only and these steps should only be performed by trained technicians. When performing this procedure make sure to wear appropriate gloves. 

  1. Disable the high voltage system using a professional bi-directional scanner such as Star Diagsnotic or Autel MaxiCOM
  2. Disconnect the 12-volt battery in the trunk.mercedes small 12 volt battery 
  3. Open the hood and locate the hybrid high voltage battery on the passenger side. hybrid battery locationOn some Mercedes-Benz models, the hybrid battery may be in the trunk.
  4. Unplug the electrical connector from high voltage battery. 
  5. Loosen the 10mm bolt and disconnect the orange cable that connects to the A/C and power electronic module. mercedes hybrid battery cable
  6. Pull the black ring up on the orange cable that comes from the DC/DC converter then pull out the cable. mercedes hybrid battery cable removed read to test
  7. Set a digital multimeter to measure current. The reading should be under 2 ohms. test mercedes hybrid battery 
  8. Measure the resistance between the two terminals shown in the picture. mercedes how to test hybrid battery s400

If the resistance is below 2 ohms the battery is ok. 

If the resistance is above 2 ohms the battery is not good and need to be replaced. 

Keep in mind that even if the battery shows under 2 ohms, it may still not charge and be faulty due to internal failure.  

This test was performed on a 2010 Mercedes-Benz S400 hybrid. 


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