Most DC converter specification mistakes are made in the first five minutes of a project, when someone reads the cabinet nameplate and orders an adapter with the same number on it. A 180 kW cabinet does not deliver 180 kW to every vehicle, and the adapter is not sized by the cabinet at all — it is sized by the current the vehicle actually requests during a session.
Start from the session, not the nameplate
Three numbers decide the electrical rating:
- Maximum current the vehicle requests. A 400 V pack charging at 150 kW draws roughly 375 A. An 800 V pack at the same power draws roughly 187 A. Higher voltage architectures reduce current for the same power, which is why 800 V vehicles are easier on connectors.
- Maximum current the cabinet can output per connector. Often lower than the cabinet total when outputs are shared.
- Continuous current the converter can hold. This is the number that matters, and it is frequently lower than the headline rating.
The converter must be rated above the lower of the first two values, with margin for ambient temperature.
Continuous versus peak: read the derating curve
A converter sold as "300 A" may hold 300 A for a few minutes and settle at 240 A in a 45 °C equipment room. Ask for two documents: the temperature rise test at rated current, and the derating curve from 20 °C to 55 °C. If the supplier cannot provide either, the rating is a marketing figure.
| Ambient | Typical usable current (300 A product) | Note |
|---|---|---|
| 20 °C | 300 A | Bench condition, rarely seen in the field |
| 40 °C | 270–300 A | Common design point for outdoor cabinets |
| 50 °C | 220–260 A | Summer in southern Europe, Middle East, US Sun Belt |
Cable length changes the answer
If the converter is a cabled version rather than a plug-in body, length matters twice. Voltage drop grows with length, and heat has more surface to dissipate but also more copper mass to warm. For runs beyond about 5 m, specify the cross-section explicitly and ask for the measured resistance per conductor rather than a nominal figure. On cable versions, 0.5 m to 10 m is a normal request range; longer than that usually means the layout should be redesigned instead.
Ingress protection should follow the site, not the catalogue
- IP54 — covered parking, indoor depot, cabinet interior.
- IP65 — outdoor pedestal with a roof or shelter.
- IP67 — exposed forecourt, coastal sites, pressure washing, temporary deployment.
Coastal and winter-salt sites also need the housing material and plating specified: silver plated contacts and a UV-stable, flame-retardant housing (PC class) age far better than bare brass in those conditions.
Mechanical life and locking
Public DC connectors see high cycle counts. 10,000 mating cycles is a reasonable floor for a well-built adapter; ask how the figure was verified. Equally important is the latch: the vehicle side and station side must both lock, and the release must not be reachable while a session is active.
Procurement checklist
| Item | What to write in the RFQ |
|---|---|
| Current | Continuous rating at 40 °C ambient, with derating curve attached |
| Voltage | DC 1000 V rated, suitable for 800 V architectures |
| Protocol | State whether a passive or active converter is required (CCS family passive; GB/T or CHAdeMO active) |
| Thermal | Temperature rise test report at rated current |
| Ingress | IP rating with test report, not a catalogue claim |
| Contacts | Plating material, contact resistance, mating cycle verification |
| Compliance | CE and FCC documentation; test reports on request |
| Traceability | Serial number per unit, batch and date code |
Frequently asked questions
Is it safe to use a 400 A adapter on a 200 A charger?
Yes. Current is drawn by the vehicle and limited by the charger; a higher-rated adapter simply runs cooler. The reverse — a 200 A adapter on a 400 A capable vehicle — is the case that overheats.
Do I need a different converter for 800 V vehicles?
The adapter must be rated for DC 1000 V to cover 800 V packs with headroom. A 500 V rated unit is not suitable, regardless of current rating.
Why do cabled versions cost more than plug-in bodies?
Copper mass, strain relief, sealing at both ends and longer assembly time. For permanent installations the cable version usually wins on thermal performance because the connector pair sits further from the cabinet heat source.
Related hardware: the GB/T to CCS2 DC adapter 300 A / 400 A, the CCS1 to CCS2 DC adapter, and the CCS2 to GB/T DC adapter 300 A. Browse the full DC converter range or send your session data for a sizing check.