Fuel cell/battery hybrid system having battery charge-level control

• US 4,931,947 A
• Filed: 02/16/1989
• Issued: 06/05/1990
• Est. Priority Date: 09/29/1983
• Status: Expired due to Fees

• Current Assignee: Anna M. Fekete, Engelhard Corporation (BASF SE)
• Original Assignee: Engelhard Corporation (BASF SE)
• Inventors: Fekete, deceased, Imre, Werth, John
• Primary Examiner(s): Teska, Kevin J.
• Application Number:
  US07/312,327
• Time in Patent Office: 474 Days
• Field of Search: 364/492, 364/493, 364/505, 364/431.01, 364/424.05, 324/415, 324/416, 307/65, 307/66, 307/80, 307/81, 180/65.3, 180/65.8, 429/7, 429/9, 320/3, 320/15, 320/61
• US Class Current: 700/297
• CPC Class Codes: B60L 58/30 for monitoring or controlling fuel cells
• CPC Class Codes: B60L 58/33 by cooling
• CPC Class Codes: H01M 16/006 of fuel cells with rechargeable batteries
• CPC Class Codes: H02J 7/34 Parallel operation in networks using both storage and other dc sources, e.g. providing buffering H02J7/14 takes precedence
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02E 60/50 Fuel cells
• CPC Class Codes: Y02T 90/40 Application of hydrogen technology to transportation, e.g. using fuel cells

Abstract

A fuel cell/battery hybrid power system is disclosed which as a microprocessor based control system. The control system enables the fuel cell to be taken out of the system by a switch when its predetermined maximum desired energy output is about to be exceeded by load requirements. The batteries are protected from overdischarge through a switch and the surge battery is selected by the battery having the highest level of charge at any given time.

Claims

1. A hybrid power source system for supplying electrical current to a load and for controlling the amount of current supplied in response to current demand from the load, the power source comprising:

a primary electrical energy source couplable to the load through a first switch means interposed therebetween and having a predetermined maximum desired power output;

first energy storage means couplable to the load in parallel with the primary electrical power source through a second switch means interposed between the first energy storage means and the load;

second energy storage means couplable to the load in parallel with both the primary electrical power source and the first energy storage means through a third switch means interposed between the second energy storage means and the load, either said primary electrical energy source, said first and second energy storage means or combinations thereof being connected in parallel to supply current to the load depending upon whether said first, said second or said third switch means or combinations thereof are appropriately energized;

load current sensing means for sensing the current flowing into the load;

charge sensor means for sensing the state of charge in said first and second energy storage means and operatively associated with said control means for enabling selection by said control means among said first and second energy storage means of the energy storage means with the highest level of charge, to serve as a surge energy storage means;

and

control means responsive to said load current sensing means for selectively energizing either said first, said second or said third switch means in a manner such that the current demand on said primary electrical energy source is maintained at or below approximately its predetermined maximum desired power output level.

2. The system of claim 1 wherein the selection of the surge energy storage means changes as the state of charge of the surge energy storage means previously selected drops below the state of charge of the other energy storage means.

3. The system of claim 1 wherein said primary electrical energy source recharges the energy storage means unselected as the surge energy storage means as needed during periods when the load is not drawing the full output of said primary electrical energy source.

4. The system of claim 1 wherein said energy storage means comprise storage batteries and said primary energy source comprises a fuel cell means.

5. The system of claim 4 wherein said storage batteries are of identical capacity.

6. The system of claim 4 wherein the number of batteries is greater than two and each said battery is connected to the load in parallel with each of the other batteries and with the fuel cell means by a switch means interposed between its associated battery and the load for connecting and disconnecting each said battery from the load.

7. A hybrid power source system for supplying electrical current to a load and for controlling the amount of current supplied in response to current demand from the load, the power source comprising:

a primary electrical energy source couplable to the load through a first switch means interposed therebetween and having a predetermined maximum desired power output;

first energy storage means couplable to the load in parallel with the primary electrical power source through a second switch means interposed between the first energy storage means and the load;

second energy storage means couplable to the load in parallel with both the primary electrical power source and the first energy storage means through a third switch means interposed between the second energy storage means and the load, either said primary electrical energy source, or said energy storage means or combinations thereof being connected in parallel to supply current to the load depending upon whether said first, said second or said third switch means or a combination thereof are appropriately energized;

load current sensing means for sensing the current flow to the load;

charge sensor means for sensing the state of charge of said first and second energy storage means; and

control means responsive to said load current sensing means and said charge sensor means (i) for selectively energizing either said first, said second or said third switch means in a manner such that the current demand on said primary electrical energy source is maintained at or below approximately its predetermined maximum desired power output level, and (ii) for connecting whichever one of said energy storage means has the highest state of charge to the load when a surge in load current demand occurs which can be satisfied by power from said primary electrical energy source and from only one of said energy storage means.