E-Scooter BMS Charger
The why
Someone stole the charger I initially bought for this project, so figured I would make my own which can be powered from USB Type-C and potentially solar.
The design
The charger is designed to provide CC-CV charging for a 6S lithium-ion pack (nominally 22.2 V, full charge ~25.2 V) from a USB-C PD source (up to 20 V / 5 A).
Key components include:
Key components include:
- USB-C PD sink controller to negotiate 20 V input
- High-efficiency buck converter (likely synchronous) to step down to battery voltage
- Current/voltage regulation loop for CC-CV behavior
- Protection features (OVP, OCP, thermal shutdown)
- Connection to the existing BQ40Z80 gas gauge for charge status monitoring
Overvoltage / undervoltage protection (ACUV / ACOV) section
Inductor selection and ripple current calculations for the buck stage
Implementation notes
The design focuses on high efficiency to minimize heat while delivering up to ~100 W charging power. USB-C PD negotiation ensures safe and flexible input power. Future revisions may include MPPT for direct solar panel input.
Conclusion
This custom charger replaces the stolen unit and adds flexibility with USB-C PD and potential solar compatibility. Testing and tuning of the regulation loop are ongoing.
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