Backup power supply project for SMS GPS Alarm 4G module .

Backup power supply project for SMS Alarm 4G GPS Trackers module or other applications.... The system uses two 18650 batteries, installed on a support, in series (3.7V each) with full charge management and voltage regulation.

General Operation:

Main Power Supply (Vin):
- Input voltage: 12V/14V (vehicle battery) through a Schottky diode to prevent reverse current.
- Voltage regulation is handled by a LM2596 Adjustable, providing a stable output of approximately 8.6V.
- The output voltage is set using resistors R1 (1kΩ) and R2 (5.6kΩ).
- A Schottky diode on the output causes a voltage drop of ~0.4V, delivering a final voltage of 8.2V after the diode.

Battery Management System (BMS):
- The BMS is powered by the 8.2V line and manages two 18650 batteries connected in series.
- Components of the BMS:
  - 2 BB3A battery management ICs.
  - 2 A2SHB MOSFETs.
  - 1 HY2120 battery management controller.
  - 2 high-power 8N03 MOSFETs to control charging and discharging.

Secondary Regulation:

- The battery output is regulated to +5V using an L1117-50CY low- dropout regulator.
- Optionally, the 5V output can be converted to 3.3V via an L1117- 33CY regulator, depending on project requirements.

Available Connection Pads:

Power connection pads for tracker:
- V Charger/Car: A4 (vehicle input voltage).
- V Batt Accu: A5 (battery voltage).
- +5V: Regulated power output.
- Vss: Ground.