System and method for connecting a first battery in parallel with a second battery by exchanging energy for equalization

Abstract

Disclosed is a battery and load equalization circuit that prevents the in-rush of current when batteries and/or loads are initially connected in parallel. Various techniques are used including charging, discharging and use of DC to DC converters to equalize charges between batteries and between batteries and capacitive loads.

What is claimed is: 
     
         1 . An energy exchange system for safely connecting a first battery in parallel with a second battery comprising:
 a controller in communication with a first battery to detect a first terminal voltage, the controller in communication with a second battery to detect a second terminal voltage;   a step-down DC to DC converter having a first input and a second output;   a switching system structured and arranged to, in a first instance, connect the first input to the first battery and the second output to the second battery, and in a second instance connect the first input to the second battery and the second output to the first battery, the switching system activated by the controller; and   a battery connector switch operable to connect the first battery and the second battery in parallel, the battery connector activated by the controller;   wherein for the first instance the controller activating the switching system to connect the step-down DC to DC converter between the first battery and the second battery when the first terminal voltage is greater then the second terminal voltage to permit a controlled transfer of charge from the first battery to the second battery in a first direction, and in the second instance the controller activating the switching system to connect the step-down DC to DC converter between the first battery and the second battery when the second terminal voltage is greater then the first terminal voltage to permit a controlled transfer of charge from the second battery to the first battery in a second direction, the controller activating the battery connector switch when the first voltage and the second voltage are sufficiently close to permit parallel connection of the first battery to the second battery without a damaging current flowing there between.   
     
     
         2 . The energy exchange system of  claim 1 , wherein the controller activates the battery connector switch when the first voltage and the second voltage are essentially equal. 
     
     
         3 . The energy exchange system of  claim 1 , wherein an initial current between the parallel connected first battery and the second battery is essentially zero. 
     
     
         4 . The energy exchange system of  claim 1 , wherein the controller indirectly directs the activation of at least one of, the step-down DC to DC, the switching system, and/or the battery connection switch. 
     
     
         5 . An energy exchange system for safely connecting a first battery in parallel with a second battery comprising:
 a controller in communication with a first battery to detect a first terminal voltage, the controller in communication with a second battery to detect a second terminal voltage;   a bi-directional DC to DC converter having a first port connected to the first battery and a second port connected to the second battery, the bi-directional DC to DC converter controlled by the controller to transfer charge and equalize the voltage between the first battery and the second battery; and   a battery connector switch operable to connect the first battery and the second battery in parallel, the battery connector activated by the controller when the first voltage and the second voltage are sufficiently close to permit parallel connection of the first battery to the second battery without a damaging current flowing there between.   
     
     
         6 . The energy exchange system of  claim 5 , wherein the controller activates the battery connector switch when the first voltage and the second voltage are essentially equal. 
     
     
         7 . The energy exchange system of  claim 5 , wherein an initial current between the parallel connected first battery and the second battery is essentially zero. 
     
     
         8 . The energy exchange system of  claim 5 , wherein the controller indirectly directs the activation of at least one of, the bi-directional DC to DC and/or the battery connection switch. 
     
     
         9 . The energy exchange system of  claim 5 , wherein the bi-directional DC to DC converter comprises:
 an inductor,   a first pair of switches disposed on opposite ends of the inductor and operable to connect the first battery to the inductor in a first polarity direction during a first phase of operation;   a second pair of switches disposed on opposite ends of the inductor and operable to connect the second battery to the inductor in a second polarity direction during a second phase of operation;   wherein the first pair of switches and the second pair of switches provide isolation between the first battery and the second battery by alternating connection to the inductor between the first phase and the second phase.   
     
     
         10 . An energy exchange system for safely connecting a first battery in parallel with a second battery comprising:
 a controller that detects a first terminal voltage of terminals of a first battery, and a second terminal voltage of terminals of a second battery;   a step-down DC to DC converter having a first input and a second output;   a switching system structured and arranged to, in a first instance, connect the first input to the first battery and the second output to the second battery, and in a second instance connect the first input to the second battery and the second output to the first battery, the orientation of connection permitting the step-down DC to DC converter to equalize charge between the first battery and the second battery, the switching system activated by the controller;   a battery connector switch activated by the controller when the first voltage and the second voltage are sufficiently close to permit parallel connection of the first battery to the second battery without a damaging current flowing there between.   
     
     
         11 . The energy exchange system of  claim 10 , wherein the controller activates the battery connector switch when the first voltage and the second voltage are essentially equal. 
     
     
         12 . The energy exchange system of  claim 10 , wherein an initial current between the parallel connected first battery and the second battery is essentially zero. 
     
     
         13 . The energy exchange system of  claim 10 , wherein the controller indirectly directs the activation of at least one of, the step-down DC to DC, the switching system, and/or the battery connection switch. 
     
     
         14 . An energy exchange system for safely connecting a first battery in parallel with a second battery comprising:
 a controller that detects a first terminal voltage of terminals of a first battery, and a second terminal voltage of terminals of a second battery;   a bi-directional DC to DC converter having a first port connected to the first battery and a second port connected to the second battery, bi-directional DC to DC converter activated by the controller to transfer charge and equalize the voltage between the first battery and the second battery; and   a battery connector switch controlled by the controller when the first voltage and the second voltage are sufficiently close to permit parallel connection of the first battery to the second battery without a damaging current flowing there between.   
     
     
         15 . The energy exchange system of  claim 14 , wherein the controller activates the battery connector switch when the first voltage and the second voltage are essentially equal. 
     
     
         16 . The energy exchange system of  claim 14 , wherein an initial current between the parallel connected first battery and the second battery is essentially zero. 
     
     
         17 . The energy exchange system of  claim 14 , wherein the controller indirectly directs the activation of at least one of, the step-down DC to DC and/or the battery connection switch. 
     
     
         18 . The energy exchange system of  claim 14 , wherein the bi-directional DC to DC converter comprises:
 an inductor;   a first pair of switches disposed on opposite ends of the inductor and operable to connect the first battery to the inductor in a first polarity direction during a first phase of operation;   a second pair of switches disposed on opposite ends of the inductor and operable to connect the second battery to the inductor in a second polarity direction during a second phase of operation;   wherein the first pair of switches and the second pair of switches provide isolation between the first battery and the second battery by alternating connection to the inductor between the first phase and the second phase.   
     
     
         19 . A method for energy exchange for safely connecting a first battery in parallel with a second battery comprising:
 providing a controller in communication with a first battery to detect a first terminal voltage, the controller in communication with a second battery to detect a second terminal voltage;   providing a step-down DC to DC converter having a first input and a second output;   providing a switching system structured and arranged to, in a first instance, connect the first input to the first battery and the second output to the second battery, and in a second instance connect the first input to the second battery and the second output to the first battery, the switching system activated by the controller; and   providing a battery connector switch operable to connect the first battery and the second battery in parallel the battery connector activated by the controller;   detecting the first terminal voltage and the second terminal voltage, wherein for the first instance the controller activating the switching system to connect the step-down DC to DC converter between the first battery and the second battery in a first direction when the first terminal voltage is greater then the second terminal voltage to permit a controlled transfer of charge from the first battery to the second battery, and in the second instance the controller activating the switching system to connect the step-down DC to DC converter between the first battery and the second battery in a second direction the second terminal voltage is greater then the first terminal voltage to permit a controlled transfer of charge from the second battery to the first battery, the controller activating the battery connector switch when the first voltage and the second voltage are sufficiently close to permit parallel connection of the first battery to the second battery without a damaging current flowing there between.   
     
     
         20 . The method of  claim 19 , wherein the controller activates the battery connector switch when the first voltage and the second voltage are equal. 
     
     
         21 . The method of  claim 19 , wherein an initial current between the parallel connected first battery and the second battery is essentially zero. 
     
     
         22 . The method of  claim 19 , wherein the controller indirectly directs the activation of at least one of, the step-down DC to DC, the switching system, and/or the battery connection switch. 
     
     
         23 . A method for energy exchange for safely connecting a first battery in parallel with a second battery comprising:
 providing a controller that detects a first terminal voltage of terminals of a first battery, and a second terminal voltage of terminals of a second battery;   providing a bi-directional DC to DC converter having a first port connected to the first battery and a second port connected to the second battery;   providing a battery connector switch operable to connect the first battery and the second battery in parallel, the battery connector activated by the controller; and   detecting the first terminal voltage and the second terminal voltage and activating the bi-directional DC to DC converter to transfer charge and equalize the voltage between the first battery and the second battery, the controller controlling the battery connector switch when the first voltage and the second voltage are sufficiently close to permit parallel connection of the first battery to the second battery without a damaging current flowing there between.   
     
     
         24 . The energy exchange system of  claim 23 , wherein the controller activates the battery connector switch when the first voltage and the second voltage are essentially equal. 
     
     
         25 . The energy exchange system of  claim 23 , wherein an initial current between the parallel connected first battery and the second battery is essentially zero. 
     
     
         26 . The energy exchange system of  claim 23 , wherein the controller indirectly directs the activation of at least one of, the bi-directional DC to DC converter, and/or the battery connection switch. 
     
     
         27 . The energy exchange system of  claim 23 , wherein the bi-directional DC to DC converter comprises:
 an inductor;   a first pair of switches disposed on opposite ends of the inductor and operable to connect the first battery to the inductor in a first polarity direction during a first phase of operation;   a second pair of switches disposed on opposite ends of the inductor and operable to connect the second battery to the inductor in a second polarity direction during a second phase of operation;   wherein the first pair of switches and the second pair of switches provide isolation between the first battery and the second battery by alternating connection to the inductor between the first phase and the second phase.