Optimal management of batteries in electric systems

• US 6,353,304 B1
• Filed: 01/19/2001
• Issued: 03/05/2002
• Est. Priority Date: 01/19/2001
• Status: Active Grant

• Current Assignee: National Technology & Engineering Solutions Of Sandia LLC (Honeywell International Inc.)
• Original Assignee: Sandia Corporation (Martin Marietta Corporation)
• Inventors: Butler, Paul C., Symons, Philip C., Corey, Garth P., Atcitty, Stanley
• Primary Examiner(s): Tso, Edward H.
• Application Number:
  US09/766,219
• Time in Patent Office: 410 Days
• Field of Search: 320/103, 320/116, 320/117, 320/119, 320/120, 320/128
• US Class Current: 320/116
• CPC Class Codes: H01M 10/06 Lead-acid accumulators semi-lead accumulators H01M10/20
• CPC Class Codes: H01M 10/30 Nickel accumulators H01M10/34 takes precedence
• CPC Class Codes: H01M 10/36 Accumulators not provided for in groups H01M10/05-H01M10/34
• CPC Class Codes: H01M 10/441 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H01M 10/446 Initial charging measures
• CPC Class Codes: H01M 10/448 End of discharge regulating measures
• CPC Class Codes: H01M 10/465 with solar battery as charging system
• CPC Class Codes: H02J 7/0019 using switched or multiplexed charge circuits
• CPC Class Codes: H02J 7/35 with light sensitive cells
• CPC Class Codes: H02J 9/062 for AC powered loads
• CPC Class Codes: Y02B 10/70 Hybrid systems, e.g. uninterruptible or back-up power supplies integrating renewable energies
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

An electric system including at least a pair of battery strings and an AC source minimizes the use and maximizes the efficiency of the AC source by using the AC source only to charge all battery strings at the same time. Then one or more battery strings is used to power the load while management, such as application of a finish charge, is provided to one battery string. After another charge cycle, the roles of the battery strings are reversed so that each battery string receives regular management.

Claims

1. In an electric system for supplying uninterrupted electric power to a load, the system having at least two battery strings and a primary AC power source, a method of optimally managing the battery strings and using the primary source efficiently comprising:

powering the load and charging all battery strings with the primary AC source;

managing one battery string while the load is powered by at least one other charged battery string and without using the primary AC source;

powering the load with at least one battery string, without using the primary AC source;

powering the load and charging all battery strings using the primary AC source; and

managing one of the other battery strings while the load is powered by at least one remaining battery string and without using the primary AC source.

2. The electric system of claim 1 wherein during the managing steps, the at least one battery string which is providing power to the load is also providing power to the battery string being managed.

3. The electric system of claim 2 wherein the at least one battery string consists of all battery strings except the battery string being managed.

4. The electric system of claim 2 wherein the battery strings are formed from either lead-acid or nickel/cadmium batteries, and during the managing step, a battery string is finish charged.

5. The electric system of claim 4 wherein the battery strings are lead-acid, and during an infrequent managing step, at least one battery string that powers the load equalizes the other battery string.

6. The electric system of claim 5 wherein said infrequent managing step occurs on the order of semi-annually.

7. The electric system of claim 4 wherein the managing step comprises providing power from the at least one power producing battery string to the finish charge battery string through a DC to DC converter.

8. The electric system of claim 7 wherein the at least one power producing battery string consists of all battery strings except the battery string being finish charged.

9. The electric system of claim 4 wherein the managing step comprises providing power from the at least one power producing battery string to the finish charge battery string through a DC to AC converter and an AC-powered finish charger.

10. The electric system of claim 9 wherein the at least one power producing battery string consists of all battery strings except the battery string being finish charged.

11. The electric system of claim 1 wherein the battery strings are nickel/cadmium or zinc/bromine, and during infrequent managing steps, the battery string being managed is completely discharged.

12. The electric system of claim 1 wherein the primary source is an AC generator, the system further comprising a photovoltaic array for generating solar-powered electricity, the invention further comprising supplementing both the generator and the power-producing battery strings with solar-powered electricity.

13. An electric system comprising:

an AC source;

a load selectively coupled through a switch to said AC source;

at least a pair of battery strings connected in parallel, each battery string having a first terminal and a second terminal, the second terminals being each connected to common negative;

a bi-directional AC-DC converter having an AC port selectively connected to receive electricity from said AC source or to provide an AC output to said load; and

a DC port selectively connected to receive a DC input from either of the first terminals of said battery strings or to provide a DC output to either of said first terminals;

a DC converter having an input connected to selectively receive power from either one of said battery strings and an output selectively connected to the first terminal of said other battery string to provide a finish charge said battery string; and

wherein said system can selectively charge all battery strings with the AC source;

power the load from at least one battery string; and

finish charge one battery string while at least one other battery string provides the finish charge and powers the load.

14. The electric system of claim 13 wherein said DC converter is a DC-DC converter and the input of said converter is selectively connected through switches directly to either of the first terminals of said battery strings.

15. The electric system of claim 13 wherein said DC converter is an AC powered finish charger having a DC output, the input of said finish charger being connected to the AC output of said bi-directional converter, either battery string being selectively connected to the DC input of said bi-directional converter, the other battery string being selectively connected to the DC output of said finish charger.