Charging 18650 with USB-C

flux

Based on Flux’s knowledge-base guidance, you can absolutely and efficiently charge a single-cell 18650 over USB-C—here’s how:
  1. USB-C Port Implementation
    • Use a CC-controller or dedicated USB-C port logic to set the correct Rp resistor on the CC line so that the upstream charger will source the desired current (e.g. 1.5 A or 3 A per USB-C spec). 〈Based on “implementing USB-C source port”〉
    • Include the usual USB-C front-end protections:
      • A small decoupling capacitor on VBUS (≥1 µF close to the connector)
      • Pull-down resistors on both CC pins (to advertise Rd if you’re sinking, or Rp if sourcing)
      • A bidirectional USB-C-rated TVS diode for ESD protection (capacitance < 1 pF per line) 〈Based on “USB Type-C projects” and “designing USB circuits”〉
  2. Single-Cell Li-Ion Charger IC
    • Select a switch-mode Li-Ion charger (not a linear LDO-style charger) that implements the CC/CV algorithm for a 3.7 V nominal (4.2 V full) cell. 〈Based on “designing single-cell li-ion battery charger”〉
    • Look for charger ICs that:
      • Accept a 5 V USB input up to 1.5 A (or higher if you negotiate PD)
      • Provide high efficiency (≥ 90%) through synchronous buck regulation
      • Integrate battery-protection and status outputs (CHG/STAT pins) for safety and user feedback 〈Based on “designing battery charger”〉
  3. Safety & User Features
    • Add polarity-protection (e.g. reverse-connected MOSFET or diode)
    • Include a PTC resettable fuse on the battery line for over-current/short-circuit safety 〈Based on “designing USB and power circuits”〉
    • Provide LED or logic-level charge-status indicators for “charging”, “full” and “fault”
In practice, chips like TI’s BQ2407x or Microchip’s MCP73871 families combine USB-C port negotiation, CC-logic, and a switch-mode CC/CV charger in one device. Using such an IC plus the recommended passives will give you a compact, highly efficient USB-C → 18650 charging solution.
Choose charger IC
Select USB-C Rp
Pick PTC fuse
Decoupling capacitor
Add placement rule
Sign up to send

Files

Pins

Symbol

Layout

3D View

No files yet