Charger spec sheets are close to useless for distinguishing good hardware from bad. Every unit claims OCPP compliance, every unit claims IP54 or better, and every unit claims a rated power it will rarely sustain. The differences that matter show up in the second year, in your field-operations budget.
The protocol questions
Ask these before anything about price. A vendor who cannot answer them clearly has not implemented OCPP properly, whatever the brochure says.
- 01Which OCPP version, and are you certified or self-declared? Ask to see the certificate.
- 02Which MeterValues measurands do you report, at what interval, and is that configurable over the protocol? You need Energy.Active.Import.Register at minimum.
- 03Do you support UpdateFirmware and GetDiagnostics? Without both, every software fault is a site visit.
- 04Do you support SetChargingProfile, and do you accept TxDefaultProfile specifically? Many units accept the message and ignore the profile.
- 05Do you maintain a local authorisation list and buffer transactions when offline? This determines whether a connectivity outage is an inconvenience or a stoppage.
- 06What is the reconnect behaviour after network loss — is there a backoff, or does it reconnect in a tight loop?
- 07Are configuration keys readable and writable over the protocol, and is there documentation of the vendor-specific ones?
What actually fails
| Component | Typical failure | Mitigation at purchase |
|---|---|---|
| Cable and gun | Wear, latch failure, vandalism, water ingress | Check the cable is separately replaceable and stock spares |
| Contactor | Sticking, especially in humidity | Ask for the rated switching cycles and the ambient specification |
| Payment terminal | Reader failure, connectivity, certification lapse | Consider whether you need one at all — QR works on every unit |
| Comms module | SIM lapse, module lock-up | Confirm remote reset of the module, and dual-SIM if available |
| Display | Sunlight readability, touch failure | Inspect a unit outdoors at noon before ordering |
| Cooling | Fan failure causing power derating | Ask what the unit does when cooling fails — derate or stop |
Rated power is not delivered power
A 60kW DC charger will rarely average 60kW across a session. Vehicle taper, state of charge on arrival and thermal derating mean 35–45kW average is a more honest planning figure. Ask the vendor for the derating curve against ambient temperature — in an Indian summer this is not a theoretical concern.
Also ask what happens on a dual-gun DC unit when both guns are in use. Many share a single power stack, so two vehicles each get half. That is fine, provided your throughput model knows it.
The environmental specification that matters
- IP rating for water and dust — IP54 is a minimum for outdoor Indian conditions, IP65 is better.
- IK rating for impact. Kerbside units get hit.
- Operating temperature range at full power, not at any power. A unit rated to 50°C that derates from 40°C is a 40°C unit.
- Humidity tolerance, which is what actually kills contactors in coastal and monsoon conditions.
Warranty clauses to read carefully
- 01Is the cable and gun covered, or excluded as a consumable? This is the most common exclusion and the most common failure.
- 02Is the warranty on-site or return-to-base? Return-to-base on a 500kg DC unit is not a warranty.
- 03What is the committed response time, and what is the remedy if it is missed?
- 04Does opening the enclosure for a routine reset void it?
- 05Is firmware support included for the warranty term, and what happens after?
Test before you commit
Buy one unit before buying twenty. Connect it to your platform and run this sequence:
- 01Complete a real session with a real vehicle and confirm the reported energy matches the unit’s own meter display.
- 02Pull the network cable or SIM mid-session and confirm the session continues and reconciles on reconnect.
- 03Issue a remote stop and confirm it lands and the session closes cleanly.
- 04Push a charging profile and read back the composite schedule to confirm the unit is enforcing it rather than merely acknowledging it.
- 05Trigger a firmware update and watch the full status trail.
- 06Leave it running for two weeks and check for heartbeat gaps and reconnect storms.