Arcbound FieldThe EVSE DirectorySubscribe
← Learn

Primer 03 · ~10 minFree

CCS session stages in the field

SLAC → SDP → CableCheck → PreCharge → CurrentDemand mapped to what you see on the gun and HMI.

CCS sessions fail at predictable stages. Name the stage before you name the part. This primer maps stages to what you see; the deep procedure lives in the free CCS handshake basics guide.

Stage map (field language)

  1. Plug / proximity / latch — Handle seats; lock engages. Failures: latch motor, debris, PP.
  2. SLAC — PLC modem finds the EV. Failures: noisy PLC, damaged handle electronics, wrong standard path.
  3. SDP — SECC discovery. Failures: SECC not responding, network-ish on the PLC path.
  4. CableCheck / isolation — IMD measures isolation. Failures: wet cable, bad gun, true ISO hardware.
  5. PreCharge — Voltage match. Failures: precharge mismatch, contactor/path.
  6. CurrentDemand — Useful power. Failures: thermal, cooling, module, vehicle abort, site power sag.

If the HMI dies at “Initializing / Communicating,” you are usually still in SLAC/SDP—not “swap a power brick.”

One gun vs whole cabinet

Isolation or latch on one connector after a cable swap is cable until a known-good gun says otherwise. Both guns or the whole stall Faulted after rain may still be seals—but also cabinet ISO, GF, or site PE. Classify before LOTO theater.

NACS and adapters

Native NACS and adapter paths fail differently. Say which one in the first ticket sentence. See free NACS field notes and samples such as NACS-H01.

Evidence pack for OEM

  • HMI photo + connector ID
  • Stage of failure (SLAC vs CableCheck vs CurrentDemand)
  • Known-good cable result
  • OCPP StatusNotification snippet
  • Weather / recent cable or coolant work

Without the stage, OEM support will ask you to gather it anyway.

Field action

Read CCS handshake basics, then open free CCS samples (CCS-H01, CCS-H03). For cooled guns, pair with liquid cooling loops.

Physical cues by stage

  • Latch buzzes then releases in seconds → often SLAC/SDP fail
  • Lock holds, display stuck on communicating → still early handshake
  • Error at isolation / insulation → CableCheck
  • Starts then collapses as kW ramps → thermal, cooling, contact resistance, or site sag

IR on the handle after a failed high-power attempt is useful when safe. Hot adapter paths are a different ticket than cold SLAC fails.

CHAdeMO on dual-standard cabinets

CCS Available + CHAdeMO Faulted is not “cabinet dead.” Use Solo CHAdeMO legacy when that is your life; otherwise do not let the CHAdeMO side distract a CCS CableCheck job.

Cooling interaction

Liquid-cooled guns fail CableCheck or derate when airlocked after service. If the stall is cooled, read liquid cooling loops before you order an ISO board.

Practice drill

Name the stage on three past tickets from memory. If you cannot, your notes were incomplete—fix the evidence pack template above on the next job.

Worked example: SLAC timeout one gun

Peer gun charges. Known-good cable moves the fault → cable/handle electronics. Fault stays → SECC/cabinet path for that connector. CCS-H01.

Worked example: PreCharge mismatch

Isolation passed; session dies as voltage should match. Now you are past CableCheck—do not replace the cable first unless evidence says so. See CCS-H04 if free/sample in corpus.

Adapter honesty

“NACS car on CCS dispenser with adapter” is a different evidence pack than native NACS overtemp. Say it early. NACS field notes.

What “stuck in Preparing” usually means

Preparing covers a wide window: plug detect, auth wait, SLAC start, early handshake. Ask which sub-stage the OEM tool shows. If the OEM UI only says Preparing, pull SECC logs or OCPP errorCode. Free CCS guide walks the ordered stages so you stop treating Preparing as a single fault class.

Isolation fail vs insulation monitoring nuisance

True CableCheck isolation fail is protective. Nuisance IM trips after rain or cable swaps need dry-down and known-good cable before SECC boards. Document ambient and last wash-down time. Link the free isolation sample when the ticket matches.

Session abort after CurrentDemand

If handshake completed and power flowed, then aborted, you are past early CCS stages—look thermal, LMS cut, payment settle, or contactor path. Do not restart at SLAC cable RMA.

Field action checklist (CCS)

  1. Confirm connector standard and adapter in use.
  2. Name the last successful stage from SECC/OEM tool.
  3. Decide cable vs cabinet with known-good swap only after stage is named.
  4. Open the matching free CCS guide section and sample entry.
  5. Only then escalate OEM RMA with stage evidence attached.

Why stage naming beats symptom naming

“Won’t charge” and “Faulted CCS” are not stages. SLAC timeout, CableCheck isolation fail, and PreCharge mismatch are. Stage names pick the sample entry and the free guide section. Symptom names send apprentices into modem trays. Make stage naming a habit on every CCS ticket before parts move.