Start a power bank OEM project with a use-case specification: rated Wh, required USB-C input/output profiles, simultaneous-port behavior, size and weight limits, recharge target, operating conditions and market-specific compliance. Capacity alone cannot prove portability, sustained output, temperature, battery life or safety.
Build the OEM Brief Around User Tasks
| Decision | Required field | Approval evidence |
|---|---|---|
| Energy reserve | Rated mAh, nominal voltage and Wh | Cell/battery specification and finished label |
| Device support | Exact USB-C fixed/PPS profiles and other ports | Protocol capture and load result |
| Multi-port use | Allocation for each port combination | Measured matrix with all active-port cases |
| Portability | Maximum dimensions and finished weight | Production sample measurement |
| Recharge | Input profiles and target recharge condition | Adapter, cable, temperature and time record |
| Market access | Target countries and required records | Exact product/model reports and label review |
Avoid requirements such as “fast charging,” “airline approved” or “safe” without the exact condition and evidence. The brief should say what the product must do and how the sample will be judged.
Rated Capacity and Delivered Energy Are Different
Convert the rated cell capacity with Wh = mAh × nominal voltage ÷ 1000. This arithmetic describes rated energy before conversion losses. It does not establish delivered output Wh, charge count or runtime. Use the mAh-to-Wh calculator to keep units and labels consistent.
Higher capacity usually needs more cell volume and weight, but the final tradeoff also depends on cell format, enclosure, protection, thermal path, PCB and connector layout. Do not publish an energy-density or “lightest” claim without a defined comparison set and measured finished samples.
Define USB Power Delivery at Profile Level
Specify the required fixed-voltage PDOs, any PPS range, maximum current and whether an EPR mode is needed. Then define behavior when multiple ports are active. A headline “100W” does not say whether the pack sustains that output, which port provides it, or what happens after another device is connected.
USB-IF documents USB Power Delivery as a negotiated power system. Product safety and battery compliance are separate from a USB data or power logo. The GaN power bank guide explains why topology labels also do not replace profile and thermal evidence.
Treat Thermal and Safety Evidence as Design Inputs
Set ambient conditions, load, duration, enclosure state and temperature measurement points before prototype testing. Record any power reduction or shutdown instead of reporting only a peak wattage. Cell and battery standards such as IEC 62133-2 address defined safety requirements; the applicable finished-product, transport and market records depend on the exact design and destination.
Never transfer a cell supplier’s report to the finished power bank as proof of every system-level claim. Keep exact cell, battery pack, BMS, enclosure and firmware revisions in the approval record.
Freeze a Reproducible Approval Sample
- Record sample ID, BOM revision, firmware and label artwork.
- Capture every advertised input/output profile.
- Run single-port and simultaneous-port load cases for a defined duration.
- Measure delivered output Wh with stated voltage, load and cutoff conditions.
- Record surface temperature locations and ambient temperature.
- Repeat connector, button, display and recharge checks after agreed conditioning.
- Define critical, major and minor incoming defects before mass production.