Field reference for EV charging technicians. 10 entries, taken from the PlugWatt app.
Reference notes from PlugWatt, the offline field toolkit for electric vehicle charging installation and service technicians. It works with no cell signal, because the sites do not have any.
Get PlugWatt on the App StoreTakes the 480 V three phase feed through input protection, contactors, and filtering into the power stack.
Phase loss or rotation faults
Loose lugs heating under load
Input contactor wear
Surge device end of life
Rectify AC to DC and convert to the commanded output voltage. Stacked in parallel slices, typically 25 to 75 kW each, so capacity degrades gracefully.
Single module failure capping output
Module fan failure and thermal derate
Module comm bus dropouts
Firmware mismatch after partial replacement
Connect the DC bus to the cable only after the handshake and cable check pass. The last switch between the bus and the driver's hands.
Welded contacts leaving the output live
Feedback or mirror contact faults
Coil supply chatter
Contact wear from cycling under load
Brings the cable and vehicle side up to bus voltage through a resistor before the main contactors close, preventing a destructive inrush across the contacts.
Open or drifted resistor
Failed precharge relay
Timeouts from added downstream capacitance
Continuously measures resistance from DC positive and DC negative to protective earth on the isolated output. Trips below roughly 100 ohms per volt, about 100 kilohms at 1000 V.
Genuine trips from moisture or damage
Capacitive leakage on long shielded runs hugging the threshold
Device failure reading permanently low
Air paths with filters and fans for the cabinet and modules; liquid loops with pump, exchanger, and coolant for high power cables and some electronics.
Blocked filters
Failed fans
Low coolant or air in the loop
Pump wear
Exchanger blockage
The user facing unit: display, payment, RFID, connector management, and the controller orchestrating the session state machine.
Controller board faults presenting as handshake failures
Display and reader failures
Dispenser to power cabinet comm faults on split architectures
Generates the J1772 pilot, runs the PLC modem for CCS and NACS digital communication, and holds the ISO 15118 certificate machinery.
Dead pilot
SLAC failures from PLC modem faults
Certificate store corruption or expiry
The wear item: power contacts, pilot and proximity pins, latch, and on high power units a liquid cooling jacket, delivered into the public's hands hundreds of times a week.
Contact wear and heating
Latch and proximity damage
Crushed or abraded cable
Coolant weep on liquid cooled assemblies
Revenue grade energy metering plus card readers and payment terminals feeding the billing chain through OCPP.
Meter faults breaking billing while power flows fine
Reader failures
Payment terminal connectivity separate from OCPP
Reference notes from PlugWatt, the offline field toolkit for electric vehicle charging installation and service technicians. It works with no cell signal, because the sites do not have any.
Get PlugWatt on the App StoreThese notes are a field aid, not a substitute for the governing codes, the stamped drawings, the authority having jurisdiction, or manufacturer manuals. Verify against the current documentation for your installed equipment.