Controlling battery states of charge in systems having separate power sources

Abstract

A control system is designed or configured to control the state of charge of a battery or battery pack in a system containing a separate power source, which is separate from the battery or battery pack. In operation, the battery or battery pack is called upon to intermittently provide power for certain functions. The separate power source may be, for example, an AC electrical power source for a UPS or an engine of a vehicle such as a micro hybrid vehicle. The battery may be a nickel zinc aqueous battery. The control system may be designed or configured to implement one or more of the following functions: monitoring the state of charge of the battery or battery pack; directing rapid recharge of the battery or battery pack from the separate power source when the battery or battery pack is not performing its functions; and directing charge to fully charged level or a float charge level, which is different from the fully charged level, in response to operating conditions.

What is claimed is: 
     
         1 . A method of controlling the state of charge of one or more nickel-zinc batteries in a battery pack for a system having (i) a separate power source working in conjunction with the battery pack and (ii) a full charge mode and a float charge mode, the method comprising:
 (a) determining that the state of charge of the one or more nickel-zinc batteries in the battery pack is below a defined level associated with the full charge mode;   (b) while in the full charge mode, applying charge to the battery pack at a first voltage to charge the one or more nickel-zinc batteries of the battery pack to a fully charged state, wherein the charge to the fully charged state is provided from the separate power source; and   (c) subsequently, while operating the system in the float charge mode, applying charge to the battery pack at a second voltage to maintain the one or more nickel-zinc batteries of the battery pack at a float charged state, wherein the charge to the float charge state is provided from the separate power source, and wherein the magnitude of the second voltage is below the magnitude of the first voltage.   
     
     
         2 . The method of  claim 1 , further comprising: before (b), determining that the separate power source is operational. 
     
     
         3 . The method of  claim 1 , wherein the separate power source is an internal combustion engine. 
     
     
         4 . The method of  claim 1 , wherein the separate power source is an AC electric power source. 
     
     
         5 . The method of  claim 1 , wherein providing the charge from the separate power source to charge the one or more nickel-zinc batteries in the battery pack in (b) and/or (c) comprises providing power from the separate power source to an alternator electrically coupled to the battery pack. 
     
     
         6 . The method of  claim 1 , wherein the system is an electrical system of vehicle. 
     
     
         7 . The method of  claim 6 , further comprising, prior to (a), discharging the one or more nickel-zinc batteries in the battery pack below the defined level associated with the full charge mode, wherein the discharging is conducted to perform an electrical function for the vehicle. 
     
     
         8 . The method of  claim 7 , wherein the electrical function comprises cold cranking an internal combustion engine of the vehicle, powering cabin electronics of the vehicle, and/or powering power steering of the vehicle. 
     
     
         9 . The method of  claim 7 , further comprising, prior to (c) partially discharging the one or more nickel-zinc batteries in the battery pack to perform the electrical function for the vehicle. 
     
     
         10 . The method of  claim 1 , wherein the system is an uninterruptable power supply. 
     
     
         11 . The method of  claim 10 , further comprising, prior to (a), discharging the one or more nickel-zinc batteries in the battery pack below the defined level associated with the full charge mode, wherein the discharging is conducted to provide backup power for the separate power source. 
     
     
         12 . The method of  claim 1 , wherein the battery pack contains exactly 7 batteries. 
     
     
         13 . The method of  claim 1 , wherein the battery pack contains exactly 8 batteries. 
     
     
         14 . The method of  claim 1 , wherein, the first voltage is between about 1.82 and 1.95 volts. 
     
     
         15 . The method of  claim 1 , wherein, the second voltage is between about 1.75 and 1.87 volts. 
     
     
         16 . The method of  claim 1 , further comprising
 determining the temperature of battery pack and/or the one or more nickel-zinc batteries in the battery pack; and   calculating the fully charged state as a function of temperature.   
     
     
         17 . The method of  claim 16 , wherein calculating the fully charged state comprises evaluating the following expression: Voltage(fully charged)=1.9−0.002*(Temperature in Celsius−22). 
     
     
         18 . The method of  claim 1 , further comprising
 determining the temperature of battery pack and/or the one or more nickel-zinc batteries in the battery pack; and   calculating the float charge state as a function of temperature.   
     
     
         19 . The method of  claim 1 , wherein charging the one or more nickel-zinc batteries of the battery pack to the fully charged state in (b) is conducted at a rate of at least about 1 C. 
     
     
         20 . The method of  claim 1 , wherein charging the one or more nickel-zinc batteries of the battery pack to the float charge state in (c) is conducted at a rate of at least about 1 C.