Power supply for a pulsed load

• US 6,998,822 B2
• Filed: 10/21/2004
• Issued: 02/14/2006
• Est. Priority Date: 05/15/2001
• Status: Expired due to Term

• Current Assignee: Cap-Xx Ltd.
• Original Assignee: Energy Storage Systems, Inc. (ESS Tech, Inc.)
• Inventors: Keshishian, Sarkis, Paul, George Lange, Turner, Geoffrey Alan, Mahon, Peter John
• Primary Examiner(s): Tso, Edward H.
• Application Number:
  US10/968,967
• Publication Number:
  US 20050077880A1
• Time in Patent Office: 481 Days
• Field of Search: 320/103, 320/123, 320/127, 320/135, 320/139, 320/166, 320/167
• US Class Current: 320/166
• CPC Class Codes: H02J 7/345 using capacitors as storage or buffering devices

Abstract

A power supply (1) for a pulsed load (2) includes a first energy storage device in the form of a battery (3) which is in parallel with a second energy storage device in the form of a supercapacitor (4). Battery (3) and supercapacitor (4) are respectively modelled as: an ideal battery (7) in series with an internal resistance (8); and an ideal capacitor (9) in series with an equivalent series resistance (ESR) (10). Through use of a supercapacitor (4) having a low ESR with respect to the resistance (8), the power supply (1) facilitates continuity of supply to load (2). That is, during peak demand more of the load current will be supplied by supercapacitor (4) due to the lower ESR. Moreover, during times of lower load current demands the battery recharges the supercapacitor. This reduces the peak current needed to be provided by the battery and thereby improves battery longevity.

Claims

1. A power supply for supplying a portable electronic device with a pulsed load profile, the power supply including an energy storage device, the energy storage device including:

a battery having a predetermined internal resistance R;

two terminals for allowing electrical connection to the battery; and

a supercapacitor connected in parallel with the terminals and having a predetermined equivalent series resistance ESR, wherein ESR<

0.25R and a capacitance provided by the supercapacitor is sufficient to limit the battery current to a predetermined maximum, the power supply having supply rails for engaging the terminals of the energy storage device.

2. A power supply according to claim 1, wherein the terminals are moved out of engagement with the supply rails to allow the like terminals of a like energy storage device to be moved into engagement with the supply rails.

3. A power supply including:

a battery for providing a battery current and having two terminals for electrically connecting with a load that demands a pulsed current; and

a supercapacitor connected in parallel with the terminals for maintaining the ratio of the RMS value of the battery current and the average value of the battery current at less than about 1.5.

4. A power supply according to claim 3, wherein the supercapacitor maintains the ratio of the RMS value of the battery current and the average value of the battery current at less than about 1.3.

5. A power supply according to claim 3, wherein the supercapacitor maintains the ratio of the RMS value of the battery current and the average value of the battery current at less than 1.1.

6. An energy storage device including:

a battery for providing a battery current and having two terminals for electrically connecting with a load that demands a pulsed current; and

a supercapacitor connected in parallel with the terminals for maintaining the ratio of the RMS value of the battery current and the average value of the battery current at less than about 1.5.

7. An energy storage device according to claim 6, wherein the supercapacitor maintains the ratio of the RMS value of the battery current and the average value of the battery current at less than about 1.3.

8. An energy storage device according to claim 6, wherein the supercapacitor maintains the ratio of the RMS value of the battery current and the average value of the battery current at less than 1.1.

9. A power supply including:

a battery having a predetermined internal resistance R and two terminals for allowing electrical connection to the battery;

a supercapacitor connected in parallel with the terminals and having a predetermined equivalent series resistance ESR, where ESR<

0.5R;

a housing for containing both the battery and the supercapacitor, the terminals being accessible from outside the housing for connecting to a load.

10. An energy storage device including:

a battery having a predetermined internal resistance R and two terminals for allowing electrical connection to the battery;

a supercapacitor connected in parallel with the terminals and having a predetermined equivalent series resistance ESR, where ESR<

0.5R;

a housing for containing both the battery and the supercapacitor, the terminals being accessible from outside the housing for connecting to a load.

11. An energy storage device including:

a battery for providing a battery current and having two terminals for electrically connecting with a load that demands a pulsed current; and

a supercapacitor connected in parallel with the terminals for maintaining the ratio of the RMS value of the battery current and the average value of the battery current at less than about 1.5.

12. An energy storage device according to claim 11 wherein the supercapacitor maintains the ratio of the RMS value of the battery current and the average value of the battery current at less than about 1.3.

13. An energy storage device according to claim 11 wherein the supercapacitor maintains the ratio of the RMS value of the battery current and the average value of the battery current at less than 1.1.

14. An energy storage device according to claim 11 wherein the supercapacitor has a predetermined equivalent series resistance ESR and the battery has a predetermined internal resistance R wherein ESR<

0.5R.

15. An energy storage device according to claim 11 including a housing for containing both the battery and the supercapacitor, the terminals being accessible from outside the housing for connecting to the load.

16. A power supply including:

a battery for providing a battery current and having two terminals for electrically connecting with a load that demands a pulsed current; and

a supercapacitor connected in parallel with the terminals for maintaining the ratio of the RMS value of the battery current and the average value of the battery current at less than about 1.5.

17. An energy storage device for supplying a load that requires a predetermined minimum load voltage, the energy storage device including;

a battery having a predetermined internal resistance R and a predetermined level of energy;

a supercapacitor connected in parallel with the battery and having a predetermined equivalent series resistance ESR, where ESR<

R, thereby reducing a voltage drop of the battery under load.

18. An energy storage device according to claim 17 wherein the reduction of the voltage drop of the battery under load allows the load to operate until the battery energy is substantially depleted.

19. An energy storage device according to claim 18 wherein the battery is a lithium ion battery.

20. An energy storage device according to claim 17 where the load is connected in parallel with the battery and the supercapacitor.

21. An energy storage device according to claim 17 wherein the reduced voltage drop extends a run time of the load.

22. An energy storage device according to claim 17 wherein ESR<

0.5R.

23. An energy storage device according to claim 17 wherein the battery has two terminals for allowing electrical connection to the load.

24. An energy storage device according to claim 23 including a housing for containing both the battery and the supercapacitor, the terminals being accessible from outside the housing for connecting to the load.

25. An energy storage device according to claim 17 wherein ESR<

R at temperatures down to about −

20C.

26. An energy storage device according to claim 17 wherein ESR<

0.5R at temperatures down to about −

20C.

27. An energy storage device according to claim 17 wherein the load is a pulsed load and the supercapacitor has a time constant RC that is greater than or about equal to the load period.

28. An energy storage device according to claim 17 wherein the supercapacitor has a leakage current of about 2 μ

Amps.

29. A power supply for supplying a load that requires a predetermined minimum load voltage, the power supply including;

a battery having a predetermined internal resistance R and a predetermined level of energy;

a supercapacitor connected in parallel with the battery and having a predetermined equivalent series resistance ESR, where ESR<

R, thereby reducing a voltage drop of the battery under load.