System and method for connecting a first battery in parallel with a second battery by charging 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 . A charging 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 first charger connected to the first battery, the first charger activated by the controller;   a second charger connected to the second battery, the second charger activated by the controller;   a switch operable to connect the first battery and the second battery in parallel, the switch activated by the controller;   wherein in a first instance the controller activating the first charger to charge the first battery to a first voltage when the first terminal voltage is less than the second terminal voltage, and in a second instance the controller activating the second charger to charge the second battery to a second voltage when the second terminal voltage is less than the first terminal voltage, the controller activating the 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 charging system of  claim 1 , wherein the controller activates the switch when the first voltage and the second voltage are equal. 
     
     
         3 . The charging system of  claim 1 , wherein an initial current between the parallel connected first battery and the second battery is essentially zero. 
     
     
         4 . The charging system of  claim 1 , wherein the first charger and the second charger are both activated by the controller to charge the first battery and the second battery to about an equal third voltage. 
     
     
         5 . The charging system of  claim 1 , wherein the controller generates a first control signal to activate the first charger, generates a second control signal to activate the second charger, and a third control signal to activate the switch to connect the first battery and the second battery in parallel. 
     
     
         6 . The charging system of  claim 1 , wherein the controller indirectly directs the activation of at least one of, the first charger, the second charger, and/or the switch. 
     
     
         7 . The charging system of  claim 1 , wherein the second charger is the first charger. 
     
     
         8 . The charging system of  claim 1 , wherein the first charger and second charger are disconnected upon equalization. 
     
     
         9 . A charging 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 first charge adjuster activated by the controller to either charge or discharge the first battery to a first voltage when the first terminal voltage is different from the second terminal voltage, the charging or discharging equalizing the voltage;   a second charge adjuster activated by the controller to either charge or discharge the second battery to a second voltage when the second terminal voltage is different from the first terminal voltage, the charging or discharging equalizing the voltage;   a 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.   
     
     
         10 . The charging system of  claim 9 , wherein the first charge adjuster is selected from the group consisting of: a first charger, a first load, a first discharging resistor. 
     
     
         11 . The charging system of  claim 9 , wherein the second charge adjuster is selected from the group consisting of: a second charger, a second load, a second discharging resistor. 
     
     
         12 . The charging system of  claim 9 , wherein the controller activates the switch when the first voltage and the second voltage are essentially equal. 
     
     
         13 . The charging system of  claim 9 , wherein the controller indirectly directs the activation of at least one of, the first charge adjuster, the second charge adjuster, and/or the switch. 
     
     
         14 . The charging system of  claim 9 , wherein an initial current between the parallel connected first battery and the second battery is essentially zero. 
     
     
         15 . The charging system of  claim 9 , wherein the first charge adjuster and the second charge adjuster are both activated by the controller to change the first battery and the second battery to about an equal third voltage. 
     
     
         16 . The charging system of  claim 9 , wherein the controller generates a first control signal to activate the first charger, generates a second control signal to activate the second charger, and a third control signal to activate the switch to connect the first battery and the second battery in parallel. 
     
     
         17 . The charging system of  claim 9 , wherein the second charger is the first charger. 
     
     
         18 . The charging system of  claim 9 , wherein the first adjuster and second adjuster are disconnected upon equalization. 
     
     
         19 . A method of charging 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 first charger connected to the first battery, the first charger activated by the controller:   providing a second charger connected to the second battery, the second charger activated by the controller;   providing a switch operable to connect the first battery and the second battery in parallel, the switch activated by the controller;   detecting the first terminal voltage and the second terminal voltage, wherein in a first instance the controller activating the first charger to charge the first battery to a first voltage when the first terminal voltage is less than the second terminal voltage, and in a second instance the controller activating the second charger to charge the second battery to a second voltage when the second terminal voltage is less than the first terminal voltage, the controller activating the 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 switch when the first voltage and the second voltage are essentially 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 first charger and the second charger are both activated by the controller to charge the first battery and the second battery to about an equal third voltage. 
     
     
         23 . The method of  claim 19 , wherein the controller generates a first control signal to activate the first charger, generates a second control signal to activate the second charger, and a third control signal to activate the switch to connect the first battery and the second battery in parallel. 
     
     
         24 . The method of  claim 19 , wherein the second charger is the first charger. 
     
     
         25 . The method of  claim 19 , wherein the controller indirectly directs the activation of at least one of, the first charger, the second charger, and/or the switch. 
     
     
         26 . The method of  claim 19 , wherein the first charger and second charger are disconnected upon equalization.