Pet Tracking Device Design

flux

Yes — multiple cells in-line along the collar is a much better architecture.
Recommended battery topology:
  • Use parallel cells: 1S2P or 1S3P, not series.
  • That keeps the pack at the same safe single-cell Li-ion voltage range for the existing charger/SIM800L design.
  • It increases capacity while allowing cells to be placed end-to-end around the collar curve.
  • Each cell should have protection/fusing or a protected pack design, because parallel Li-ion cells need safe balancing and fault protection.
Runtime impact:
  • 1× 3500 mAh cell: ~20.8 mA average available for 7 days — borderline.
  • 2× 3500 mAh in parallel: ~41.7 mA average available — much safer.
  • 3× 3500 mAh in parallel: ~62.5 mA average available — strong margin.
  • With the earlier conservative estimate around 20.6 mA average, 2 cells should comfortably meet 7 days, assuming decent cellular/GPS signal and proper sleep firmware.
Design recommendation:
  • Use 1S2P 18650 cells as the baseline.
  • Keep 5-minute location updates as default.
  • Keep SIM800L/GPS sleep modes mandatory.
  • Mechanically, distribute the cells along the collar and connect them with flexible wiring or a rigid-flex harness; do not rely on the PCB itself to bend sharply around cylindrical cells.
I still can’t save this into the project because your access is comment-only, but the electrical direction is now clear: 1S2P 18650 pack + 5-minute reporting is the practical baseline.
Use 1S2P baseline
Explain pack wiring
Add protection details
Optimize power design
Check manufacturability
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VUSB
STM_RST
SWCLK
SIM_TX
SWDIO
P4
VBAT
3V3
P3
R4
Resistance
5KΩ
R5
Resistance
5KΩ
VBAT
J1
J3
J4
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Pet Tracker Device

Pet Tracker Device thumbnail
This is a Pet Tracker Reference Design based on STM32L4. Tracker connects with network by SIM800L module connected to the STM. Also MCU connected to the GPS by uart and send data to server #STM32 #GPS #G4 #G3 #LTE #IoT #Tracker #smartHomeDevices #referenceDesign #edge-computing #edgeComputing #stm #template #referenceDesign

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