Short answer: eight specifications decide whether a DC converter works in your fleet — direction, continuous current, peak current and duration, working voltage, protocol board type, ingress protection, operating temperature, and certification. Get any one wrong and the unit either refuses to start a session or derates in the field. This checklist is the one our engineers run through with every OEM and fleet buyer.
1. Direction — vehicle side or station side?
Decide from the vehicle first. A Chinese GB/T car charging at a European CCS2 station needs GB/T → CCS2. The same station serving a European car in China needs CCS2 → GB/T. They are different products with different plug geometry. Write the sentence “the car is ___ and the station is ___” before opening a catalogue.
2. Continuous current, not marketing current
Ask for the continuous rating at 40 °C ambient, and the temperature-rise test result. A unit advertised as “300 A” that reaches 70 K rise at 250 A will derate or trip on a hot afternoon. Our reference points: 125 A for 50 kW CHAdeMO routes, 250 A for 100–150 kW, 300 A continuous for 350 kW-class stations, 400 A peak for short high-power bursts.
3. Working voltage and insulation
DC 1000 V covers 800 V architectures and most 500 V packs with margin. Check the withstand voltage (typically 1500 V test) and the pollution degree assumed for the housing.
4. Protocol board: integrated or external?
CCS1, CCS2 and NACS use PLC; CHAdeMO and GB/T use CAN. If the vehicle's BMS stack must be emulated, the board is doing real work and should be:
- field-updatable,
- rated for the ambient range of the site,
- isolated from the power path,
- documented with the supported protocol revisions (ISO 15118-2/-20, DIN 70121, GB/T 27930, CHAdeMO 1.0/1.2).
5. Environment: IP rating and temperature
| Site | Minimum IP | Temperature range |
|---|---|---|
| Indoor depot, covered canopy | IP54 | −10 to +45 °C |
| Outdoor station, temperate | IP65 | −20 to +50 °C |
| Outdoor, cold climate (RU/Nordics) | IP65–IP67 | −30 to +45 °C, cold-impact housing |
| Coastal / high humidity | IP67 | salt-mist tested contacts |
6. Mechanical life and cable option
Ask for mating cycles (10 000 is a reasonable baseline for a plug-type unit used daily) and whether a cable version exists. Cable versions (0.5–10 m) move the mechanical load off the station's own connector and are common for retrofit projects where the existing cable is short.
7. Certification for the destination market
- EU/UK: CE (LVD + EMC), RoHS; consider EN 61851-1 alignment.
- USA/Canada: FCC Part 15 for the board, UL recognition preferable for fleet procurement.
- Russia/Eurasia: EAC if the buyer's customs requires it.
- Middle East: CE is normally accepted; sand/dust ingress is the practical issue.
8. Commercial terms that reveal the supplier
- Sample lead time — 3–7 days for a real factory, weeks for a trading layer.
- MOQ flexibility — 1 pc samples and 50 pcs OEM is a normal factory answer.
- Test report per unit — hi-pot, insulation, temperature rise and IP seal, serialised. Ask to see one.
- Warranty and spares — 12 months is standard; ask what a replacement board costs, because that number tells you whether the product is serviceable.
Frequently asked questions
How many converters does a 20-station site need?
One per station that must serve a non-native vehicle, plus 10–20 % spares. Operators who serve mixed fleets normally standardise on two directions rather than buying all twenty.
What is the failure mode to worry about most?
Thermal, not electrical. Loose or oxidised contacts raise resistance, resistance raises temperature, and the session either derates or the housing deforms. Silver-plated contacts plus a temperature sensor in the plug head is the mitigation.
Can one converter cover both 400 V and 800 V cars?
Yes — voltage is set by the station. A 1000 V-rated converter works across both architectures; the limitation is current, not voltage.