xEV Battery, Drive Motor, and Power Electronics Service
Traction battery
A pack contains modules, busbars, contactors, a service disconnect, a battery management system (BMS), and often liquid thermal management. The BMS monitors cell voltage, temperature, state of charge, and isolation resistance. When servicing, use insulated tools, keep the work area clean and dry, torque terminals to spec, and never lay tools on the pack. Modules must be balanced and matched; mixing states of charge or capacity causes faults.
Drive motor
Most xEVs use permanent-magnet synchronous motors. Spinning the rotor generates voltage, so lock the rotor or disconnect the three-phase cables before service. Handle resolvers and rotor position sensors carefully, and keep magnets away from metal debris and sensitive electronics.
Power electronics
Inverters, DC-DC converters, and onboard chargers contain large capacitors and IGBT/SiC devices. After disabling, confirm the DC bus has decayed. If capacitor voltage lingers, suspect the active or passive discharge circuit rather than assuming the meter is wrong. Observe ESD precautions and never open a pack or inverter housing unless trained and authorized.
Traps
Spinning a motor to "check it" with HV connected; reusing single-use HV connectors or seals; over- or under-torquing busbars; assuming a low 12 V battery is the cause of every no-start; and ignoring coolant leaks into the pack.
Worked example
Inverter replacement: disable HV, wait 10 minutes, verify 0 V at the inverter DC bus, then confirm capacitor decay with the meter before removing the cover. If voltage remains above spec, stop and diagnose the discharge circuit.