Power supply unit

1. A method for controlling the supply of power to a parking meter comprising:

a) monitoring, by a control unit, the status of a main battery which is rechargeable and a back-up battery which is replaceable and non-rechargeable;

b) charging at least partially, by the control unit, the main battery via one or more charging sources;

c) supplying power, by the control unit, to the parking meter primarily from the main battery;

d) switching the supply of power, by the control unit, to come from the back-up battery when the voltage across the main battery falls below a predetermined level; and

e) signaling, by the control unit, a wireless communication device to communicate a status message to a control system external to the parking meter regarding the state of the main battery, the back-up battery, or the one or more charging sources;

wherein the main battery, the back-up battery, the wireless communication device, and the control unit are received within the parking meter.

2. The method of claim 1 , wherein the status message comprises one or more of: battery charge rate, remaining battery charge, remaining battery life, real-time current supplied by a charging source, average current supplied by a charging source, error messages indicating battery failure, error messages indicating charging source failure, real-time power consumption, and average power consumption.

3. The method of claim 1 , wherein the wireless communication device communicates the status message over a telecommunications network.

4. The method of claim 1 , further comprising switching the supply of power, by the control unit, back to the main battery when the main battery is sufficiently recharged.

5. The method of claim 4 , further comprising minimizing the supply of power from the back-up battery after switching the supply of power to come from the main battery.

6. The method of claim 1 , wherein the main battery consists of one to five cells.

7. The method of claim 1 , wherein the back-up battery consists of one to five cells.

8. The method of claim 1 , wherein the one or more charging sources comprises one or more solar panels.

9. The method of claim 8 , wherein the parking meter comprises a diode coupled to the one or more solar panels to prevent reverse current from flowing into the one or more solar panels.

10. The method of claim 1 , wherein the predetermined level is 5.5V.

11. The method of claim 1 , wherein the back-up battery has a nominal supply voltage greater than that of the main battery.

12. The method of claim 1 , wherein the parking meter is a single space parking meter or a dual space parking meter.

13. The method of claim 1 , wherein the parking meter is a multi-space parking meter.

14. A power supply for supplying power to a parking meter comprising:

a) a main battery which is rechargeable;

b) a charging arrangement for connecting the main battery to one or more charging sources;

c) a back-up battery which is replaceable and non-rechargeable;

d) a connection to a wireless communication device for communicating a status message regarding the state of the power supply, the main battery, the back-up battery, or the one or more charging sources to a control system external to the parking meter; and

e) a connection to a control unit for controlling supply of power to the parking meter primarily from the main battery and secondarily from the back-up battery;

wherein the main battery, the back-up battery, the wireless communication device, and the control unit are received within the parking meter.

15. The power supply of claim 14 , wherein the status message comprises one or more of: battery charge rate, remaining battery charge, remaining battery life, real-time current supplied by a charging source, average current supplied by a charging source, resistance at various sections within the power supply, error messages indicating battery failure, error messages indicating charging source failure, real-time power consumption of the parking meter, and average power consumption of the parking meter.

16. The power supply of claim 14 , wherein the wireless communication device communicates the status message over a telecommunications network.

17. The power supply of claim 14 , the control unit is configured to switch the supply of power back to the main battery when the main battery is sufficiently recharged.

18. The power supply of claim 17 , wherein the control unit is configured to minimize the supply of power from the back-up battery after switching the supply of power to come from the main battery.

19. The power supply of claim 14 , wherein the main battery consists of one to five cells.

20. The power supply of claim 14 , wherein the back-up battery consists of one to five cells.

21. The power supply of claim 14 , wherein the one or more charging sources comprises one or more solar panels.

22. The power supply of claim 21 , wherein the power supply comprises a diode coupled to the one or more solar panels to prevent reverse current from flowing into the one or more solar panels.

23. The power supply of claim 14 , wherein the back-up battery has a nominal supply voltage greater than that of the main battery.

24. The power supply of claim 14 , wherein the parking meter is a single space parking meter or a dual space parking meter.

25. The power supply of claim 14 , wherein the parking meter is a multi-space parking meter.