A pre-shipment inspection (PSI) is the last point where you can find a problem while the goods are still at the factory and the balance is usually still unpaid. For EV chargers, which carry mains voltage and spend years in garages and driveways, it is also a safety check. This guide covers how AQL sampling works, what an inspector should test on a charger, and how to write it into your order. For the wider project view, see our OEM and private-label EV charger guide.
A PSI does not replace sample testing or certification. Its job is to confirm that the mass-produced lot matches the approved sample and the agreed specification.
How AQL sampling works
Inspectors rarely check every unit. They draw a random sample from the finished lot and accept or reject the whole lot based on the defects they find. The rules most contracts point to are in ISO 2859-1. ISO published a new edition, ISO 2859-1:2026, in January 2026, replacing the 1999 edition that inspection agencies have used for many years. Many purchase orders still say only ‘ISO 2859-1’, so state the edition you mean and confirm your inspection agency works to it.
The logic is the same in principle under either edition:
- Lot size: the number of units in the batch being inspected.
- Inspection level: general level II is the usual default; special levels use smaller samples for tests that are slow or destructive.
- Sample size: read from the standard’s tables using the lot size and inspection level.
- AQL: the acceptance quality limit set for each defect class, which gives the accept and reject numbers for that sample.
AQL is not a promise that the lot contains a given percentage of defects. It is a sampling rule that controls how often a lot of a certain quality will be accepted, so the values you choose should reflect how serious each type of defect is.
Defect classes for EV chargers
Agree the defect classes in writing before production starts, with examples and photos. Many importers use zero tolerance for critical defects, 2.5 for major and 4.0 for minor, but the right values depend on your product, market and risk appetite.
| Class | Meaning | EV charger examples |
|---|---|---|
| Critical | Could cause injury or breaks a legal requirement | Failed hi-pot or earth continuity, protection does not trip, exposed live parts, missing or wrong rating label |
| Major | Likely to cause failure or a return | Will not start a charging session, wrong connector or plug, wrong cable length, cracked housing, app will not pair |
| Minor | Cosmetic, unlikely to affect use | Small scratches, slight colour variation on the logo, crooked carton label |
What to check on a charger
Function and safety
- Charging session: connect each sampled unit to an EVSE tester or a vehicle and confirm it moves through the control pilot states, closes its relay and delivers current at each selectable setting.
- Protection: use the test function or a test load to trigger the residual current or ground-fault protection and confirm the unit trips and shows the correct fault.
- Hi-pot and earth: review the factory’s production records for dielectric withstand (hi-pot) and earth continuity tests, and ask for a witnessed test on a few samples using calibrated equipment.
- Display and app: on LCD and smart models, check the boot logo, charging graphics, Wi-Fi or Bluetooth pairing and firmware version.
Labels, cable and packaging
- Rating label: model, ratings, serial number and the marks for the target market, legible and in the agreed place. In the EU the CE marking must be visible, legible and indelible.
- Other markings: the WEEE bin symbol and importer details for EU and UK shipments, and the FCC statement where required in the US. Our article on rating labels and required markings lists them by market.
- Cable and plug: measure the cable length, confirm the grid plug and vehicle connector match the order, and check the strain relief at both ends.
- Branding: logo position and colour against the golden sample, plus a tape test on printed logos.
- Packaging: carton marks, barcodes, manual language, the storage case if ordered, and a carton drop test.
Timing and the golden sample
Inspections are usually booked when production is complete and most of the order is packed, so the inspector can pull cartons at random. Keep a signed golden sample at the factory and one in your office; it is the reference for colour, logo, labels and packaging. Before booking, make sure your own sample checks are done. Our guide on testing an EV charger sample before a bulk order covers what to approve first.
Tests that take a long time or damage the unit, such as a temperature-rise run or a drop test, use a much smaller special sample. Agree those numbers in advance so there is no argument on the day.
Writing inspection into the order
- Name the standard and edition, the inspection level and the AQL for each defect class.
- Attach the checklist and the defect list with photos.
- State who books and pays for the inspection, and who pays for re-inspection after a failed lot.
- Link the balance payment to a passed inspection report, as explained in our guide to payment terms for OEM orders.
- Agree what happens to a failed lot, for example rework and 100% sorting followed by re-inspection.
Inspecting an EVDANCE order
EVDANCE handles engineering, injection molding, assembly and testing in-house in Shenzhen, so an inspector can see the production line and test stations in one place. Your dedicated account engineer can prepare the approved sample references and test records ahead of the visit. To see the site before you order, take the factory tour, or talk to our team about your inspection plan.
Key Takeaways
- A pre-shipment inspection checks that the mass-produced lot matches the approved golden sample and the agreed specification.
- ISO 2859-1:2026 replaced the 1999 edition in January 2026, so name the edition in your purchase order.
- Set separate AQL values for critical, major and minor defects, with zero tolerance for safety-critical faults on chargers.
- Check function, protection, hi-pot records, labels, cable, plug and packaging, and tie the balance payment to a passed report.
Sources & Standards
- International Organization for Standardization (ISO) — ISO 2859-1:2026 Sampling procedures for inspection by attributes, Part 1
- International Organization for Standardization (ISO) — ISO 2859-1:1999 Sampling procedures for inspection by attributes, Part 1
- Your Europe (European Union) — CE marking
- Your Europe (European Union) — WEEE label: what does it mean, EU requirements
