Single-cell LiFePO4 protection circuit (overcharge, overdischarge, charge/discharge overcurrent, overtemperature, undertemperature) used in the Ambient project.

For more details, please refer to the Git repository and the Ambient project README.

Main features

• LiFePO4 charge/discharge protector (HYCON HY2112-CB)
• Overcharge protection (i.e., overvoltage from charging circuit): >= 3.75 V (0.15 V hysteresis) up to 12 V.
• Overdischarge protection (i.e., cell undervoltage): <= 2.10 V (0.20 V hysteresis).
• Charge overcurrent (i.e., shorted or high-leakage cell): >= 2 A.
• Discharge overcurrent (i.e., shorted or high-consumption load): >= 2 A.
• Temperature cutoffs (Texas Instruments TMP390):
• Charge overtemperature: >= 54 °C (5 °C hysteresis).
• Discharge overtempeture: >= +60 °C (5 °C hysteresis).
• Charge undertemperature: <= 0 °C (5 °C hysteresis).
• Discharge undertemperature: <= 20 °C (5 °C hysteresis).
• Thermal fuse (SETFuse X18):
• Thermal failsafe: >= 86 °C
• Overcurrent failsafe: 3 A

Fabrication notes

PCB

Standard 2-layer 0.8mmmm stackup:

• 2 layers (front/back),
• 0.8mm thickness (enclosure clearance constraint),
• 1oz copper,
• FR-4 dielectric,
• HASL finish.

No special requirements, any solder mask and silkscreen color.

Gerbers, BOM and position files are provided but can be re-generated from the KiCad project

Assembly

Recommended automated assembly for top-side. No bottom-side assembly.

Manual assembly for top side:

• BT1 18650 cell holder (through-hole),
• F1 thermal fuse (through-hole, observe manufacturer's soldering recommendations).

Acknowledgment

This project has received funding from Université Côte d'Azur and CERN.