Key HV Components – Overview
400–800 V DC
Traction Battery Pack
Lithium-ion cells in modules; the main energy store. Contains BMS (Battery Management System) for cell monitoring, temperature control and safety shutdowns.
Power Electronics
Inverter / Motor Controller
Converts DC battery voltage to AC for the electric motor and regenerates AC back to DC during braking. Contains large capacitors that retain dangerous charge after de-energisation.
Drivetrain
Electric Drive Motor
Typically a permanent magnet synchronous motor (PMSM) or induction motor. Even with the HV system de-energised, the motor can generate back-EMF when rotated – a residual HV hazard.
AC Charging
On-Board Charger (OBC)
Converts mains AC (Level 1/2 charging) to the vehicle's DC battery voltage. Contains isolation transformers and power electronics operating at mains voltage.
12 V Supply
DC-DC Converter
Steps down HV battery voltage to 12 V to power conventional vehicle systems. Replaced the alternator in ICE vehicles. Maintains galvanic isolation between HV and LV systems.
Safety
Manual Service Disconnect (MSD)
A plug or switch that physically interrupts the HV battery circuit. Removing the MSD is typically the first step of any HV de-energisation procedure.
Qualification Levels and Component Access
DGUV 209-093 defines which qualification level is required to work near or on each component type:
- Level S/E (Sensibilisierte Person): Awareness of HV hazards; may work on low-voltage systems but must recognise and avoid HV components
- Level 1S/1E – Fachkundig unterwiesene Person (FuP): May perform general maintenance near HV components under FHV supervision; cannot de-energise independently
- Level 2S/2E – Fachkundige Person Hochvolt (FHV): May independently de-energise, verify voltage-free state and work on all HV components in the voltage-free state
- Level 3S/3E (FHV – Live Working): Additionally authorised to perform diagnostics and measurements on energised HV systems
The Inverter Capacitor Hazard
One of the least understood HV hazards: inverters contain large electrolytic capacitors that can store several thousand joules of energy at full battery voltage. After removing the MSD, these capacitors take time to discharge – typically 5–15 minutes. Touching inverter HV terminals before they have discharged can be fatal even after the MSD is removed. This is why capacitor discharge wait time is a mandatory step in every de-energisation procedure.
Are orange cables always HV?
In modern vehicles, orange cable insulation is the standard indicator of HV wiring (above 60 V DC). However, this is a convention rather than a universal legal requirement. Some older vehicles and non-automotive HV equipment may use different colour coding. Always verify the system voltage before assuming any cable is safe to touch.