ISO 15118

Standards evolve, vehicles change, and sites can’t stand still. The good news: many DC fast chargers can add newer connectors without starting from zero—if you line up electrical headroom, signal integrity, software, and compliance in the right order.     Industry snapshot (dated milestones that shape upgrades) SAE moved the North American connector from an idea to a documented target: a technical information report in December 2023, a Recommended Practice in 2024, and a dimensional spec for the connector and inlet in May 2025.   Major networks have publicly said they’ll offer the new connector at existing and future stations by 2025, while equipment makers shipped conversion kits for existing DC fast chargers as early as November 2023. Separately, one network reported its first pilot site with native J3400/NACS connectors in February 2025, adding a second in June 2025. Some Superchargers are open to non-Tesla EVs when the car has a J3400/NACS port or a compatible DC adapter.   What this means for you: plan for dual-connector coverage where traffic is mixed, and treat cable-and-handle swaps as the first option when your cabinet’s electrical, thermal, and protocol limits already fit the new duty.   Upgrade paths (pick the lightest that works) Cable-and-handle swap: replace the lead set with the new connector while keeping cabinet/power modules. Lead + sensor harness refresh: Add temperature sensing at the pins, tidy the HVIL circuit, and reinforce shielding/ground continuity so the data channel stays stable and thermal derating unfolds smoothly. Dual-connector add: keep CCS for incumbents and add J3400 for new traffic. Cabinet refresh: step up only if voltage/current class or cooling is the real blocker.     Retrofit flow (from idea to live energy) Map vehicles to support (voltage window, target current, cable reach). Check cabinet headroom (DC bus & contactor ratings, isolation-monitor margin, pre-charge behavior). Thermals (air vs liquid; sensor placement at the hottest elements). Signal integrity (shield continuity, clean grounds, HVIL routing). Protocols (ISO 15118 plus legacy stacks; plan contract certificates if offering Plug & Charge). CSMS & UI (connector IDs, price mapping, receipts, on-screen prompts). Compliance (labels, program rules; keep a per-stall change record). Field plan (spare kits, minutes-level swap procedures, acceptance tests, rollback).     Engineering noteHandshake stability lives inside the handle and lead as much as in firmware. Stable contact resistance, verified shield continuity, and clean grounds protect the data channel that rides on the power lines. As practical reference points, assemblies such as Workersbee high-current DC handle embed temperature sensing at hot spots and maintain continuous shield paths so current steps are smooth rather than abrupt.   Can I just swap the cable and handle? Often yes—when the cabinet’s bus window, contactors, pre-charge, cooling, shield/ground continuity, and protocol stacks already meet the new duty. Where you must keep CCS available or the cabinet wasn’t built for retrofits, use dual leads or stage conversions by bay.     Five bench checks before field work Bus & contactors: ratings meet or exceed the new connector’s voltage/current duty. Pre-charge: resistor value and timing handle the vehicle inlet capacitance without nuisance trips. Thermals: cooling path has margin; pin-temperature sensing is in the right place (near the hottest elements). Signal integrity: shield continuity and low-impedance drains end-to-end; clean grounds. Protocol stacks: ISO 15118/Plug & Charge where needed; certificate handling planned.     Retrofit readiness scorecard Dimension Why it matters Pass looks like What to check Bus & contactors Safe close/open at target duty Ratings ≥ new duty; thermal margin intact Nameplate + type tests Isolation & pre-charge Avoid nuisance trips on inrush Stable pre-charge across models Log plug-in → pre-charge separately Thermal path Predictable current steps, not hard cuts Sensors at hot spots; proven cooling path Thermal logs during soak Signal integrity Clean handshake beside high current Continuous shield & ground; low noise Continuity tests; weather-band trials Serviceability Short incidents, fast recovery Labeled spares; no special tools Swap order: handle → cable → terminal UI & CSMS Fewer support calls Clear prompts; consistent IDs & receipts Price and contract mapping tests Compliance Avoid re-inspection surprises Labels and paperwork aligned Per-stall change record   Field-proven acceptance tests Cold start: first session after overnight; log plug-in → pre-charge and pre-charge → first amp as two metrics. Wet handle: light exterior spray (no flooding); confirm clean handshake. Hot soak: After sustained operation, confirm the charger reduces current in controlled steps rather than with abrupt cutoffs. Longest lead bay: confirm voltage drop and on-screen messaging. Reseat: single unplug/replug; recovery should be quick and clean.     FAQs Can existing DC fast chargers be upgraded to new connectors?Yes in many cases—starting with a cable-and-handle swap when electrical, thermal, and protocol checks pass. Some vendors provide retrofit options; others recommend new builds for units not designed for retrofits.   Will we alienate CCS drivers if we add J3400?Keep dual connectors during the transition. Several networks have committed to adding J3400/NACS while retaining CCS.   Do we need software changes?Yes. Update connector IDs, price logic, certificate handling, and UI messages so receipts and reports stay consistent.   Is ISO 15118 required for new connectors?Not universally, but it enables contract-at-the-cable and structured power negotiation, and pairs well with J3400 rollouts.   Upgrades succeed when mechanics, firmware, and operations move together. Do the lightest change that delivers a clean start and a predictable ramp—then make that swap repeatable across bays.

You plug in, the screen wakes, and energy starts to move. In those first seconds the vehicle and the charger agree on identity, limits, and safety. ISO 15118 provides the shared protocol that lets the car and charger agree on the terms of a session. It sits above the metal and seals inside the connector, turning a mechanical mate into a predictable digital exchange.     What ISO 15118 actually doesISO 15118 defines the messages and timings an EV and a charging system use during a session. It covers capability discovery, contract-based authentication, pricing and schedule updates, and how both sides should respond to faults. With a shared protocol, a car can authenticate at the cable, a site can shape power in real time, and logs can be tied to vehicles rather than swipe cards.   How data rides through a physical connectorThe same assembly that carries hundreds of amps also carries a narrowband data signal. In most public DC systems outside China, that signal rides on the power conductors while dedicated pins confirm presence and allow high-voltage contactors to close. Stable contact resistance, shield continuity, and clean ground paths keep the channel intact. When any of those slip, the station shows a “communication” fault even though the root cause is mechanical or environmental.   Plug & Charge—what changes at the startPlug & Charge uses certificates so the vehicle can present its contract at the moment of insertion. The charger checks that contract and starts the session without cards or apps. Sites see shorter queues and fewer support calls. Fleet operators get charging records mapped to vehicle asset IDs, making cost allocation and audits straightforward.   Smart power, scheduling, and bidirectional readinessBeyond a basic current cap, ISO 15118 supports negotiated power ceilings, scheduling windows, and contingency rules when conditions change. Depots can smooth peaks and schedule topping sessions across a shift. Highway sites can share limited capacity across many bays with predictable ramps instead of abrupt cuts. The same building blocks prepare hardware and software for wider vehicle-to-grid use as markets mature.     From plug-in to power-on: how a charging session unfolds Handle seats and locks; proximity and presence circuits confirm a safe mate. A communication link forms; roles are set and capabilities exchanged. Identity is presented; if enabled, a contract is verified at the cable. Limits are agreed: voltage window, current ceiling, ramp profile, thermal plan. The charger aligns bus voltage and closes contactors under supervision. Current ramps to the profile while both sides monitor and adjust. The session stops; current ramps down, contactors open, and a receipt is recorded.     Buyer and operator scorecard Dimension What it looks like on site Why it matters What to ask vendors for Handshake reliability First-try starts during peak hours Fewer queues and retries Success rates by temperature and humidity bands Time to first kWh Seconds from plug-in to energy Real throughput, not just nameplate power Distribution data and acceptance targets Plug & Charge readiness Contract at the cable, no cards or apps Shorter lines, cleaner logs Certificate lifecycle tooling and renewal process Thermal derating clarity Predictable current steps as heat rises Driver trust and reliable ETAs Pin-temperature sensing and on-screen messaging behavior EMC discipline Stable comms next to high current Fewer “phantom” protocol faults Shielding/ground design and continuity test results Serviceability Minutes-level swaps for handles and cables Lower downtime and callout costs MTTR targets, labeled parts, video procedures Lifecycle documentation Limits, inspection cadence, failure modes in simple terms Safer, repeatable operations across shifts Maintenance schedule and acceptance tests     Engineering notesTreat shielding and ground as first-class design elements. Verify shield continuity across the full assembly and route drains with low-impedance terminations. Place temperature sensors close to the hottest elements so current steps are smooth rather than abrupt. As a practical reference point, some high-current DC handles—such as Workersbee high-current DC handle—embed sensing near hot spots and maintain continuous shield paths from handle to cabinet. These choices reduce “mystery” faults in busy windows.     Field observationsMost handshake retries show up on chilly mornings, with damp connectors, and during hot, sun-soaked afternoons. Condensation inside cavities and loose ground lugs inject noise into the data channel. Balancing sealing and venting, adding a quick torque check to the inspection routine, and routing cables to avoid sharp bends cut retries sharply. Assemblies with verified shield continuity and grounding—e.g., Workersbee ISO 15118-ready connector assemblies—help keep the data path quiet when current and heat are high.     Implementation details you can verify• Every build lot should include checks for shield continuity and ground resistance, plus a temperature-rise spot test at representative currents. • On site, measure two timing metrics separately: plug-in to pre-charge, and pre-charge to first amp. If either drifts, inspect mechanics before software. • Track aborted starts per hundred plugs by bay and by cable age; patterns often reveal a specific run or routing issue.     Service playbook excerptWhen a “communication error” appears, work the order: visual inspection → ground continuity → shield continuity → temperature-sensor sanity check → trial session. Replace parts in the sequence handle → cable → terminal assembly to minimize downtime. Aim for minutes-level recovery. Keep a labeled spare kit and a short video procedure at each site.     Why connector and cable choices decide protocol stabilityA connector that stays dry internally, holds its torque, and keeps low contact resistance protects the data channel that rides on the power lines. Good ergonomics reduce twisting and side loads that loosen lugs over time. Clear labeling and minutes-level swaps turn a site incident into a short pause instead of a lane closure. This is where specification sheets meet operations: signal integrity and thermal behavior live or die inside the handle and along the cable, not just in the cabinet.     Driver tips that reduce errors• Insert with the handle aligned; avoid twisting under load.• If a fault appears, reseat once, then try a neighboring bay.• After rain or washing, wipe the inlet face to clear moisture films that can couple noise into the channel.• Watch for on-screen notes about planned current steps; a gentle ramp usually signals thermal management, not a failure.     Key takeaways for fleets and site ownersMake ISO 15118 a requirement in RFQs and acceptance tests. Measure more than uptime by tracking handshake success, time to first kWh, and recovery after a reseat. Standardize spares and labels so field teams replace the right part on the first visit. Keep certificate updates on a schedule and hold grounding continuity to the same standard you apply to thermal limits. Do these well and sessions start clean, climb predictably, and stay stable during rush hours.