Power Bank Capacity Rating: What the Box Number Really Means
TITLE: Power Bank Capacity Rating: What the Box Number Really Means DESC: A milliamp-hour figure without a named test condition is not a specification. Here is what to demand from a supplier before you sign a PO. KEYWORDS: power bank capacity rating, rated capacity test condition, power bank mAh explained, discharge condition power bank, battery capacity specification TAGS: power banks, battery compliance, procurement, UN38.3 Q: Why does my supplier's mAh figure differ from what customers report? A: Cell capacity and rated output capacity are measured at different points in the circuit, at different discharge currents and different cut-off voltages. Unless the datasheet names those conditions, the box figure describes a laboratory cell, not the energy a buyer actually receives. Q: Is a higher mAh claim always better for my listing? A: No. A high claim that cannot be traced to a named test condition is a compliance and returns risk, and market surveillance authorities in the EU and UK can ask you to substantiate it. Ask for the test condition before you ask for a bigger number.A power bank is sold on one number, and that number is usually the least defensible figure on the packaging. Capacity claims are quoted at cell level, at output level or at some unstated midpoint, and each gives a different result. For a purchasing manager, the question is not which figure is largest but whether the figure can be traced to a test condition that survives scrutiny. Without that traceability, you are not buying a specification; you are buying a sentence.
Cell capacity, rated capacity and what sits between them
The cell inside the enclosure has a nominal capacity determined by its chemistry and format. Between that cell and the USB port sit a conversion circuit, protection, and often a boost stage, each of which consumes energy. The number a customer experiences is the energy delivered at the port under a defined load, down to a defined cut-off voltage, at a defined ambient temperature. Change any one of those and the delivered figure moves. This is why two products with identical cells can publish different numbers and both be honest, and why a supplier who quotes only one figure without conditions is telling you nothing you can defend.
When you request a quotation from our power banks and portable chargers range, you receive a datasheet tied to the hardware revision being quoted. No capacity, wattage or cycle figure is published before that datasheet exists, because a figure that floats free of a revision is a figure nobody can test against.
The conditions a rated capacity claim must name
Ask your supplier to state the discharge current, the cut-off voltage, the ambient temperature and whether the figure is measured at the cell or at the output port. Ask which laboratory performed the measurement and on which sample. If the answer arrives as a marketing deck rather than a test report, treat the claim as unverified. The table below is the checklist we use when a buyer asks us to justify a number.
| Item to confirm | Why it matters to the importer |
|---|---|
| Measurement point | Cell-level and port-level figures differ; the packaging claim must say which one it is |
| Discharge current | A figure taken at a low current will not be reproduced by a phone drawing fast charge |
| Cut-off voltage | Where the test stops determines how much energy is counted |
| Ambient temperature | Capacity behaviour changes with temperature; state the test condition |
| Hardware revision | A datasheet applies to one revision; a change of cell or circuit invalidates it |
| Watt-hour rating on the unit | Required for transport documentation and used by your forwarder |
| Test summary and SDS | Every battery order ships with the UN38.3 test summary and safety data sheet |
Compliance runs alongside the number, not behind it
A capacity claim sits inside a document set. For EU placement you will work through CE RED, covering EN 300 328, EN 301 489 and EN 62368-1, plus RoHS 3 and REACH SVHC screening; UKCA is available on request. Certification is a test scope booked per hardware revision with an accredited laboratory, not a status a factory holds in perpetuity, so a certificate issued for an earlier build does not cover the unit in your next container. Our charger certification by country checklist sets out how the scopes differ across your markets.
Transport is the second gate. Lithium cells travel under UN38.3, and your forwarder will ask for the test summary, the safety data sheet and the watt-hour rating printed on each unit. The UN38.3 shipping file walkthrough lists what that conversation requires before a booking is accepted. Note also that WEEE, BattG, DEEE/Triman and EORI/VAT obligations sit with the importer in the EU and UK, not with us.
Where an importer should say no
Walk away from a quotation that offers a capacity figure with no test condition attached, that cannot name the revision the datasheet describes, or that promises a certification the supplier has not yet booked. Walk away if the sample you receive carries no watt-hour marking, or if the supplier treats UN38.3 paperwork as something to produce after the order. These are not negotiating positions; they are the points where a cheap unit becomes an expensive recall.
- Ask for the datasheet revision number and match it to the sample serial.
- Confirm the measurement point, current, cut-off voltage and temperature in writing.
- Request the UN38.3 test summary and SDS with the quotation, not after deposit.
- Confirm which certification scope is booked, for which revision, at which laboratory.
- Check the watt-hour rating is printed on the unit itself, not only the carton.
- Agree who holds WEEE and battery registration in each destination market.
Commercial terms worth settling early
Standard MOQ is 500 units, with logo at 500, custom packaging at 1,000 and firmware or app white-label at 2,000. Stock samples ship in 3-5 days and configured samples in 7-15, with sample cost credited against mass production; production runs 25-35 days, or 12-20 weeks where ODM tooling is involved. Terms are EXW, FOB Shenzhen or DDP by air or sea, with a 12-month warranty and 2 % free replacement parts shipped with the order. QC runs through IQC, IPQC, FQC and OQC at AQL 2.5 major and 4.0 minor. The MOQ, sampling and lead times page sets out the detail, and customisation tiers explains what changes at each volume.
If you want to see how these gates are applied on the line, the factory section describes our build and test flow, and the document checklist for importers is a useful template even for non-watch categories. Send us the capacity claim you are being asked to accept, together with the datasheet revision it refers to, and we will tell you which test conditions are missing before you take it to your compliance team via talk to the factory.
Questions buyers ask
Why does my supplier's mAh figure differ from what customers report?
Cell capacity and rated output capacity are measured at different points in the circuit, at different discharge currents and different cut-off voltages. Unless the datasheet names those conditions, the box figure describes a laboratory cell, not the energy a buyer actually receives.
Is a higher mAh claim always better for my listing?
No. A high claim that cannot be traced to a named test condition is a compliance and returns risk, and market surveillance authorities in the EU and UK can ask you to substantiate it. Ask for the test condition before you ask for a bigger number.
Related: more on power banks & charging · buyer guides · customisation tiers