Solar and battery powered long lasting tracker
A solar-powered position tracker includes a load including one or more of a GPS module, a GPS antenna, a GSM module, or a GSM antenna. The load is powered by a rechargeable battery, which may be charged by one or more of a non-rechargeable primary battery and a solar cell. The solar-powered position tracker includes a battery management system for powering the position tracker by controlling the solar cell, rechargeable battery and the non-rechargeable primary battery. The two-stage battery management system charges the rechargeable battery in two stages and includes a solar management and protection circuit interconnecting the solar cell, and the rechargeable battery. The battery management system is configured to execute a charging process for recharging the rechargeable battery from solar cell and protect the rechargeable battery under a high pulse current discharge process to meet a high current or high pulse current discharge demand by the load.
1. A solar-powered position tracker comprising:
a load including one or more of a GPS module, a GPS antenna, a GSM module, or a GSM antenna;
a rechargeable battery;
a non-rechargeable primary battery;
a solar cell;
a battery management system for powering the position tracker by controlling the solar cell, the rechargeable battery and the non-rechargeable primary battery, the battery management system charging the rechargeable battery in two stages and including a solar management and protection circuit interconnecting the solar cell and the rechargeable battery;
wherein the battery management system is configured to execute a charging process for recharging the rechargeable battery from solar cell and protect the rechargeable battery under a high pulse current discharge process to meet a high current or high pulse current discharge demand by the load,
wherein the two-stage charging process comprises:
detecting, by the battery management system, whether an output voltage of the rechargeable battery falls below a low voltage threshold;
when the output voltage of the rechargeable battery falls below the low voltage threshold:
directing, by the battery management system, a flow of electrical current to charge the rechargeable battery cells from the non-rechargeable primary battery until the output voltage of the rechargeable battery reaches a partially-charged voltage threshold indicating that the rechargeable battery is not yet fully charged; and
switching, by the battery management system, to direct a flow of electrical current from the solar cell to charge the rechargeable battery for its remaining capacity until the rechargeable battery is fully charged.
2. The solar-powered position tracker of claim 1 , wherein the solar management and protection circuit is configured to:
monitor an open circuit voltage of the solar cell periodically by disconnecting for a short period time the solar cell and a DC-DC boost converter and measuring the solar cell voltage, wherein the DC-DC boost converter being in an electrical connection path between the solar cell and the rechargeable battery;
during the solar cell being in connection with the rechargeable battery via the DC-DC boost converter, continuously monitors and controls the solar cell voltage at approximately 80% of the open-circuit voltage using a maximum power point tracking (MPPT) controller to achieve a maximum power output of the solar cell.
3. The solar-powered position tracker of claim 1 , wherein the solar management and protection circuit is configured to:
disconnect the rechargeable battery from the load when an under-voltage condition is detected; and
disable a charging of the rechargeable battery by the solar cell when an over-voltage condition is detected.
4. The solar-powered position tracker of claim 1 , wherein the high pulse current discharge process comprises:
directing the rechargeable battery to provide a majority of power to the load and the solar cell to provide a limited power to the load;
when the output voltage of the rechargeable battery falls below the low voltage threshold:
directing the non-rechargeable primary battery to provide power to the load.
5. The solar-powered position tracker of claim 1 , wherein the rechargeable battery is a lithium-ion battery.
6. The solar-powered position tracker of claim 1 , wherein the non-rechargeable primary battery is a lithium-thionyl chloride battery.
7. The solar-powered position tracker of claim 1 , wherein the a battery management system includes a step-up regulator circuit.
8. The solar-powered position tracker of claim 1 , wherein the solar management and protection circuit includes a DC-DC boost converter, a programmable dynamic maximum power point tracking controller, an under-voltage protection circuit, and an overvoltage protection circuit.
9. The solar-powered position tracker of claim 8 , wherein the programmable dynamic maximum power point tracking controller periodically disengages an electrical pathway between the solar cells and the DC-DC boost converter to measure an open-circuit voltage of the solar cell.