Importing chargers and power supplies from China
The category where a 30-cent saving can burn your brand: verify real power, why safety certification is not negotiable and what to check in the cable.
A 65 W charger is quoted on 1688 at USD 4, and the version that saves thirty cents comes out of the same mould and the same box: what changes is the transformer, the Y capacitor and the opto-coupler — the three parts that separate the 5 V output from the 127 V mains. None of them can be seen in a photograph, so this category is bought against a specification and verified with sustained load, temperature and an insulation test. The usual minimum is between 500 and 2,000 units per reference.
Why this category is not bought like an accessory
On a phone case, a defect costs you a return; on a charger it costs you a fire or an electric shock, and that changes what “cheap” means. The product takes 127 or 220 V from the mains and puts it inside a box the user leaves plugged in all night: the only barrier is insulation a few millimetres thick and a handful of components. Nobody can tell a good one from a bad one, because both charge the same way: the failure appears at six or eighteen months, never when the lot arrives.
How real power is verified: sustained, not peak
The figure on the box is usually peak power — what the chip holds for a few seconds; what matters is the power the charger sustains at thirty minutes. It is tested with a programmable electronic load: declared power continuously for half an hour, logging voltage and current and measuring enclosure and winding temperature. The two typical failures appear there: the voltage collapses after a few minutes, when the transformer saturates or thermal cut-off engages, or the product holds and burns. The test is repeated at low mains voltage: a charger that declares 100–240 V and was tested at 230 V may sustain nothing at 100 V, which is the reality across much of Mexico and Brazil.
IEC 62368-1: the standard that replaced 60950
The safety standard for a power supply is today IEC 62368-1, fourth edition published in 2023, which replaced IEC 60950-1 — information technology — and IEC 60065 — audio and video — after the coexistence period that closed in December 2020 in Europe and the United States. In Brazil, Ato ANATEL nº 5155/2024 set the safety requirements for mobile phone chargers and replaced the reference to IEC 60950-1 with IEC 62368-1.
The standard dropped prescriptive rules and classifies power supplies by energy class, each with its own safeguard. Insulation between primary and secondary has to be reinforced, and the transformer, the Y capacitor and the opto-coupler must be of types that have already been evaluated. A factory can keep the enclosure and the look of the board and substitute the transformer for an unevaluated equivalent at half the price: the report stops covering the product even though the box is identical.
“CE” without a technical file is a sticker
CE marking is a self-declaration by the manufacturer: it rests on a signed declaration of conformity naming the manufacturer and the standards applied, and on a technical file containing the test reports. If the supplier cannot deliver both — with the laboratory identified and the reports citing EN IEC 62368-1 — what they are showing you is a sticker.
What a customs broker asks for is the certificate, not the self-declaration: the European one does not replace a Mexican NOM or a Brazilian homologation, which are numbered documents issued by a body accredited in the destination country and verifiable in the issuer’s public register. And the holder is the importer, not the factory: “I already have certification” is only worth anything if the answer states for which market and in whose name.
Protection: four circuits you cannot see in a photo
Overcurrent, overvoltage, overtemperature and short circuit are four different protections and none of them appears in a photograph: that is why a factory can remove them without it showing when the lot arrives.
- Current limiting. Voltage falls in a controlled way instead of the switching transistor failing short.
- Overvoltage. It cuts the output when the feedback loop loses control: the failure in which a 5 V charger delivers 12 V.
- Thermal cut-off. It acts when the transformer or the switch goes past its limit.
- Short circuit. It withstands a shorted output indefinitely — a cable trapped in a seat — and recovers on its own.
The fuse and the Y capacitor perform the same function on the mains side: a Y capacitor that fails short is the mechanism by which mains voltage reaches the USB output.
None of them is verified by looking, but by asking the charger for more than it declares: current is raised above the rating and the charger is checked to limit or cut, and the output is shorted for one minute.
The cable: the specification that is in no datasheet
Two cables that look identical on the outside can carry half the current, and the difference is in the conductor cross-section. A 28 AWG wire has 0.21 Ω per metre; a 20 AWG one, 0.033 Ω. Because current flows out and back, the resistance that counts is double: 0.42 Ω per metre with the thin one and 0.066 Ω with the thick one. At 3 A that is a 1.3 V drop against 0.2 V.
The consequence is not cosmetic. A phone receiving 3.7 V instead of 5 V does not only charge more slowly: it reads the charger as incapable and drops to the minimum regime. It is measured without destroying anything: the voltage difference between the charger output and the device input, divided by the current, is the loop resistance. And a USB-C cable rated above 3 A has to carry an e-marker chip: without it the device stays at 3 A no matter how much more the charger promises.
Fast charging: the protocol has a name
“Fast charging” is not a magnitude: it is the result of the charger and the phone speaking the same protocol, and a charger can be excellent and still not fast-charge your particular phone. One that supports only Quick Charge 3.0 will charge an iPhone at 5 V, because the iPhone negotiates USB PD; one with PD but without PPS will not fast-charge a Samsung. The terms that have to be put in writing:
- USB PD version (2.0, 3.0 or 3.1) and the fixed voltages it offers, and on which port.
- PPS, with its adjustable range — 3.3–11 V, 3.3–16 V or 3.3–21 V — and the step in millivolts.
- Quick Charge version and proprietary protocols: Huawei’s SCP and FCP, OPPO’s VOOC, vivo’s FlashCharge.
- Whether the power is per port or total: most multiport units share one controller, and 65 W becomes 45 plus 20 when a second device is plugged in.
A charger that advertises fast charging without naming the protocol is describing the connector, not the product.
Plug, voltage and certification: the three destinations
The three destinations do not share a plug, and two of the three do not share a voltage: getting it wrong turns the lot into unsellable stock, and it is not fixed with an adapter if the cable is moulded to the enclosure.
| Requirement | Mexico | Argentina | Brazil |
|---|---|---|---|
| Plug | A and B, flat | I, three flat pins (IRAM 2073) | N (NBR 14136) |
| Voltage | 127 V, 60 Hz | 220 V, 50 Hz | 127 or 220 V depending on the region, 60 Hz |
| Certification | NOM-003-SCFI-2014 or NOM-001-SCFI-2018 depending on classification, plus NOM-024-SCFI-2013 for labelling | Electrical safety by category, framework of Resolución 169/2018, body accredited by the OAA and a local holder | ANATEL for the mobile phone charger (Ato nº 5155/2024); Inmetro for the rest, with a Brazilian legal entity as holder |
| If it emits radio | CRT homologation | ENACOM | ANATEL; since 25 May 2026, importing for sale requires prior homologation |
In all three cases the certificate is obtained before shipping, because the test is carried out on the finished product, and the holder is the importer. A 100–240 V, 50/60 Hz input solves all three markets; a fixed 220 V unit does not work in Mexico or in much of Brazil. The detail is in the certification matrix.
Table: what to specify, what to measure and what disqualifies a lot
| Point | What is specified | What is measured | What disqualifies the lot |
|---|---|---|---|
| Power | Sustained per port, not peak; total and split | Electronic load at the declared power, 30–60 min | Falls away or cuts on thermal before 30 min |
| Temperature | Enclosure temperature declared at rated load | Thermocouple on enclosure and winding, at 25 °C | Exceeds the declared value or trips thermal cut-off |
| Protections | OCP, OVP, OTP and SCP with thresholds | Overcurrent above the rating and a sustained short circuit | Delivers more current than declared or does not recover |
| Insulation | Reinforced primary-secondary, evaluated components | Dielectric test on the finished unit | Arcing or leakage; transformer, Y-cap or opto-coupler without a reference |
| Cable | Minimum conductor cross-section | Voltage drop at rated current | Drop above 5% of the output voltage |
| Protocol | PD, PPS and QC with ranges, plus proprietary ones | Actual agreement with the target phones | Negotiates nothing above 5 V |
| Documents | Destination certificate and its holder | Verifiable number in the body’s register | Certificate for another model or in another importer’s name |
MeliPrep bills pre-shipment AQL inspection at USD 299 per inspector-day (ISO 2859-1, level II, AQL 2.5 / 4.0) and coordinates destination certifications at cost.
MOQ and tooling: why a custom enclosure dominates the first order
The usual minimum is between 500 and 2,000 units per reference, and what pushes it up is not assembly but the mould — the same tooling arithmetic that governs the rest of the Shenzhen electronics catalogue. A custom enclosure requires an injection mould that is paid for once and quoted by cavities, steel, sliders and finish; on a first order it usually costs more than the goods and only amortises above several thousand units.
And there is a consequence that is often forgotten: a new enclosure restarts the certification, because the certificate covers one model and a change of housing alters thermal behaviour and insulation distances. For a first order, the reasonable route is to start from a model already certified for the destination and limit customisation to the packaging and the label.