Specialist EV and Hybrid High-Voltage Diagnostics and Repair UK
High-Voltage Testing, Inverter Diagnostics, BMS Analysis, and Component Repair
Has your electric or hybrid vehicle shut down due to an insulation resistance fault, drivetrain error, battery management lockup, or power inverter failure? Main dealerships routinely decline component-level repairs on high-voltage (HV) systems, opting instead to replace complete battery packs or entire motor-generator drive units at costs that often exceed the vehicle value.
AXION Automotive provides safe, certified high-voltage diagnostics, bench testing, inverter circuit repair, and battery control module analysis for garages and vehicle owners across the UK.
We diagnose and repair complex electrical faults across pure EV and hybrid powertrains, prioritizing component-level fixes over complete unit replacements.
High-Voltage Diagnostics and Repair Capabilities
High-Voltage Isolation and Insulation Resistance Testing
When high-voltage contactors open and disable the vehicle due to detected electrical leakage:
Megohmmeter Insulation Testing: Precision bench and vehicle insulation testing up to 1000V to locate breakdown points across wiring harnesses, drive motors, and AC compressors.
Contactor and Pre-Charge Circuit Diagnostics: Identifying welded main contactors, blown pyrofuses (pyroswitches), and damaged pre-charge resistors.
Inverter and Power Electronics Repair
Inverter Gate Driver Board Testing: Diagnosing burnt IGBT / MOSFET power switching transistors and gate drive controllers within drive units.
DC-DC Converter Diagnostics: Repairing step-down converters responsible for keeping the 12V auxiliary system charged from the main traction battery.
On-Board Charger (OBC) Bench Repairs: Fixing AC charging faults, internal filter capacitor burnouts, and charge port communication lockouts.
Battery Management System (BMS) Diagnostics
Cell Supervision Circuit (CSC) Repairs: Resolving individual module monitoring faults, internal thermistor errors, and cell voltage measurement dropouts.
BMS Crash Data and Interlock Resets: Resetting high-voltage interlock loop (HVIL) fault codes and safety shutdown flags following an incident or deep discharge.
State-of-Charge (SoC) and Health (SoH) Diagnostics: Pinpointing weak cell groups, balance issues, and degraded modules before entire packs fail.
Common EV and Hybrid Faults We Resolve
Vehicle Will Not Enter Ready Mode: Caused by HV isolation loss, interlock circuit open loops, or stuck high-voltage relays. Resolved via component-level isolation tracking and relay replacement.
Drivetrain Malfunction or Inverter Error: Caused by thermal failure in inverter drive circuits or phase sensor dropouts. Resolved through gate driver rebuilds and sensor renewal.
On-Board AC Charging Failure: Vehicle fails to initiate or complete charging from home wallboxes or public AC chargers due to internal charger circuit degradation.
Battery Isolation Faults (High Resistance to Ground): Triggered by coolant seepage, humidity ingress, or failing AC compressor insulation.
Auxiliary 12V Battery Flattening: DC-DC converter failing to step down high voltage, leaving the low-voltage electronics unpowered.
Supported EV and Hybrid Platforms
We handle high-voltage and power electronic systems across major hybrid and battery-electric platforms:
Toyota and Lexus Hybrid Synergy Drive: Inverter assemblies, DC-DC modules, and hybrid battery control units.
Volkswagen Group (VAG): ID.3, ID.4, Audi e-tron, and GTE plug-in hybrid drive electronics and BMS modules.
BMW and Mini: i3, i8, i4, and PHEV high-voltage batteries, electrical machine electronics (EME), and range-extender systems.
Mercedes-Benz: EQ series and hybrid high-voltage power electronics and battery management controllers.
Hyundai and Kia: Ioniq, EV6, Kona, and Niro power control units (EPCU) and on-board chargers.
Tesla: Model S, 3, X, and Y high-voltage component testing, contactor boxes, and drive unit electronics.
How Our Service Works
Submit Vehicle Fault Details: Provide your vehicle registration, fault codes, diagnostic scan logs, and symptoms.
Safe Assessment and Intake: For localized electronic sub-modules (such as inverters, on-board chargers, or BMS controllers), modules can be securely packaged and posted to our Didcot technical facility.
Certified High-Voltage Testing: Technicians inspect circuits using high-voltage safety gear, insulation testers, and bench simulation equipment.
Component Repair and Verification: We execute micro-soldering, component renewal, or software resets.
Insured Return Delivery: Serviced modules are bench verified and returned via tracked courier.
Frequently Asked Questions
Do you repair high-voltage components or just replace complete assemblies?
We focus on component-level diagnostics and repair. Rather than replacing an entire motor or battery pack, we identify and fix specific failed sub-components, such as gate drivers, sensors, contactors, or control boards.
What should I do if my hybrid or EV is in safety shutdown mode after a flat 12V battery?
Many EV/hybrid vehicles lock their high-voltage contactors if the auxiliary 12V system dies or suffers erratic voltage spikes. We can test and clear hard safety lockouts from your battery control module on the bench to restore normal contactor operation.
Can I send an on-board charger or inverter module by post?
Yes. As long as high-voltage components are fully disconnected, discharged, and safely removed by a qualified technician, modular electronics such as DC-DC converters, BMS control units, and on-board chargers can be sent to our workshop via courier.
Request Your EV or Hybrid Diagnostic Quote Today
Get an assessment from our automotive electronics bench team:
Workshop Address: Unit 2, Long Wittenham Rd, Didcot, Oxfordshire, OX11 9BH
Technical Inquiries: support@axionautomotive.co.uk
Direct Line: 07440 134303