Secondary electrical power supply

A power supply system, comprising:

• (a) a primary DC power supply powered by a utility power source;
• (b) an auxiliary power supply alternatingly operable in a charge or discharge mode and connected to and energized solely by said primary DC power supply, said auxiliary power supply comprising:
• (i) a controllable DC to DC converter having high voltage and low voltage terminals, said high voltage terminals being connected to the primary DC power supply and said low voltage terminals establishing a DC voltage level which is substantially less than the voltage level of the primary DC power supply;
• (ii) rechargeable battery means having a terminal voltage whose level equals, is greater or is lower than the voltage level of the primary DC power supply in some predetermined amount, said battery means having a first terminal connected to a first side of said primary DC power supply;
• (iii) circuit means connecting the low voltage terminals of said converter between a second terminal of said battery means and a second side of said primary DC power supply;
• and
• (iv) said converter being operative for controlling the voltage of said low voltage terminals in correspondence with the load imposed on the primary DC power supply and the terminal voltage of said battery means, thereby controlling the charge and discharge of the battery means;
• and
• (c) whereby, energy is transferred from said primary DC power supply to said auxiliary power supply battery means when said auxiliary power supply is in a charge mode, and energy is transferred from said battery means and added to the energy provided by said primary DC power supply when said auxiliary power supply to said load is in a discharge mode.