The 5-Step De-Energisation Procedure
DGUV 209-093 and manufacturer-specific work instructions define the exact steps. The following reflects the general sequence – always follow the vehicle-specific manual:
- Identify the vehicle and assess hazards – confirm the vehicle type, battery voltage level (typically 400 V or 800 V DC) and check the risk assessment is current
- Don PPE – put on Class 0 insulating gloves (EN 60903), safety glasses and insulated work boots before approaching the HV system
- Activate the service disconnect / manual service disconnect (MSD) – follow the manufacturer's procedure exactly; this disconnects the battery from the HV circuit
- Wait for capacitor discharge – high-voltage capacitors in the inverter can retain dangerous charge; wait the time specified by the manufacturer (typically 5–10 minutes)
- Verify voltage-free state with a CAT III multimeter – measure at the prescribed test points; voltage must be below 60 V DC; record the reading in the test record
Who May Perform HV De-Energisation?
De-energisation is a core competency of the FHV (Fachkundige Person Hochvolt) qualification. The minimum requirements are:
- Level 2S qualification for series/production vehicles (after SoP)
- Level 2E qualification for development vehicles, prototypes and pre-production vehicles
- Valid qualification certificate and up-to-date annual briefing
- Familiarity with the specific vehicle type's service documentation
An Fachkundig unterwiesene Person (FuP) (Level 1S) may not independently de-energise an HV vehicle and may not verify voltage-free state.
Required Equipment
- Class 0 insulating gloves (EN 60903, up to 1,000 V) – for de-energisation of standard production vehicles
- CAT III multimeter – for voltage-free verification; must be in calibration
- Insulated tools to EN 60900 – only use when accessing HV components
- Lock-out/tag-out devices – to prevent inadvertent re-energisation during work
- Vehicle-specific work instruction – manufacturer manuals specify exact disconnect locations and wait times
Does de-energisation need to be documented every time?
Yes. Every de-energisation must be documented in a
test record including the measured residual voltage, the instrument used, the FHV's name and signature, and the vehicle identification. This documentation is not merely best practice – it is an employer liability requirement under BetrSichV.
Can the vehicle be re-energised after de-energisation without a new procedure?
No. If an HV vehicle is reconnected (re-energised) after de-energisation, the full de-energisation procedure must be repeated before further work begins. The voltage-free state cannot be assumed to persist once the work area has been left or the vehicle has been accessed by another person.