Charging current split
The purpose of this test is to evaluate the charging split between the vehicle's Low Voltage (LV) auxiliary (12 V) and High Voltage (HV) battery systems when being charged by single-phase Mode 2 Electric Vehicle Supply Equipment (EVSE).
High Voltage (HV) electrical systems have high voltage cabling, stored electrical energy, retained hazardous voltages, and the potential to affect medical devices.
Risk of damage to equipment and property, risk of electric shock, personal injury, or death, and risk of explosion and fire.
- Read carefully and understand the hazards and risks described above.
- Only work on HV systems if you are a qualified technician, have received appropriate type-specific training from a qualified electrician, and hold valid accreditation.
- Do not work with HV systems if you have been fitted with a pacemaker or other electronic medical devices.
- Always refer to the vehicle manufacturer’s information sources to identify the actions you must take to prevent danger.
- Use equipment and accessories in accordance with their safety guides.
- Always wear appropriate Personal Protective Equipment.
How to perform the test
- Use the manufacturer's data to identify the On Board Charger (OBC), vehicle charging port HV inlet cables, the LV battery earth cable and the OBC to HV battery cable.
- Make sure the vehicle's HV battery is not fully charged (to ensure the EVSE will provide a charge when connected to the vehicle).
- Connect a high amps clamp to Channel A and the HV L1 or HV neutral cable from the vehicle charging port inlet to the OBC.
- Connect a high amps clamp to Channel B and the HV cable from the OBC to the HV battery.
- Connect a high amps clamp to Channel C and the LV battery earth cable.
- Connect the Mode 2 charger to a domestic socket outlet and switch it on.
- Minimize the help page. You will see that PicoScope has displayed an example waveform and is preset to capture your waveform.
- Start the scope.
- Connect the Mode 2 charger connector cable to the vehicle charging port.
- With your waveforms on screen stop the scope.
- Use the Waveform Buffer, Zoom and Measurements tools to examine your waveform.
Further guidance
Both the LV auxiliary (12 V) and HV batteries and their charging systems are critical to the correct operation of an EV. It is not hard to imagine how an improperly charged HV battery might cause vehicle range issues or how a depleted auxiliary battery might cause the vehicle to become powerless (or dead").
However, there is an additional side effect that an auxiliary battery fault can also cause HV battery charging problems. As such, it is critical that the auxiliary battery is of the correct type and specification for the vehicle and remains in good states of charge and health (see here for an example of what can happen in the opposite case).
A poor or failing auxiliary battery might be detected after the EVSE is connected to the vehicle, as it first delivers charge: An auxiliary battery with a high internal resistance will draw more charge, reducing the charge available to the HV battery. In this way, it is possible that a faulty auxiliary battery could cause a HV battery to never be fully or properly charged. The test described here shows how the charge from the EVSE is distributed between the LV and HV battery systems. As such, it is a good test to help identify whether one of these systems is causing a charging fault.
This test assumes that a single phase Mode 2 type charger is being used. However, it is possible to perform the test with 3 phase chargers: consult the vehicle manufacturer's data to identify a suitable input charging phase instead of the L1 or Neutral cable described above. Note that the test is also suitable for both Type 1 and Type 2 charging connectors.
Not all auxiliary batteries are charged directly from the vehicle's OBC unit. Some vehicles use a separate DC-DC converter to charge the auxiliary battery. However, in the majority of cases, the LV ground/chassis cable will be connected to the auxiliary battery negative terminal.
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.
