Staggered backup battery charging system

• US 7,345,455 B2
• Filed: 11/18/2004
• Issued: 03/18/2008
• Est. Priority Date: 11/18/2004
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Jones, Carl E.
• Primary Examiner(s): Vu; Bao Q.
• Assistant Examiner(s): DIAO, M BAYE
• Application Number:
  US10/991,914
• Publication Number:
  US 20060103352A1
• Time in Patent Office: 1,216 Days
• Field of Search: 320/110, 320/112, 320/128, 320/148, 320/9, 320/157, 320/158, 320/132, 320/134, 320/135, 320/149, 320/118, 320/119, 320/120, 320/121, 320/122, 320/125
• US Class Current: 320/148
• CPC Class Codes: H02J 7/0013 acting upon several batteries simultaneously or sequentially H02J7/1423 takes precedence

Abstract

A battery backup system includes a control device including a power sensing device, a discharge circuit, a charging circuit, and a plurality of battery packs. A lower threshold is established representative of a minimum acceptable effective energy capacity. Each battery pack is recharged if its effective energy capacity falls below the lower threshold. Additionally, an upper threshold is established representative of the minimum acceptable effective energy capacity plus a performance margin. In a two battery-pack system, if both battery packs fall below the upper threshold, the battery with the least effective energy capacity is discharged to the minimum acceptable effective energy capacity and then recharged to the battery pack'"'"'s maximum energy capacity. In this way, both battery packs are prevented from approaching the minimum acceptable effective energy capacity at the same time. This reduces the size or number of battery packs and reduces their associated cost and volume.

Claims

1. A backup-battery system, comprising:

a first battery pack having a first effective energy capacity and a first maximum energy capacity;

a second battery pack having a second effective energy capacity and a second maximum energy capacity;

a charging circuit electrically connected to the first and second battery packs;

a control device including a power sensor and a lower threshold and an upper threshold;

wherein said power sensor is adapted to detect when the first energy capacity falls below the lower threshold and the control device is adapted to direct the charging circuit to charge the first battery pack to the first maximum energy capacity;

wherein the power sensor is further adapted to detect when the first energy capacity and the second energy capacity fall below the upper threshold and the control device is further adapted to direct the charging circuit to charge the first battery pack to the first maximum energy capacity;

a third battery pack having a third effective energy capacity and a third maximum energy capacity;

wherein the power sensor is further adapted to detect when any two of the energy capacities have fallen below the upper threshold and the control device is further adapted to direct the charging circuit to charge the first battery pack to the first maximum energy capacity; and

a discharge circuit electrically connected to the first, second, and third battery packs and the control device is further adapted to direct the discharge circuit to discharge the first battery pack to the lower threshold before directing the charging circuit to charge the first battery pack to the first maximum energy capacity.

2. A backup-battery system, comprising:

a first battery pack having a first effective energy capacity and a first maximum energy capacity;

a second battery pack having a second effective energy capacity and a second maximum energy capacity;

a charging circuit electrically connected to the first and second battery packs;

a control device including a power sensor and a lower threshold and an upper threshold;

wherein said power sensor is adapted to detect when the first energy capacity falls below the lower threshold and the control device is adapted to direct the charging circuit to charge the first battery pack to the first maximum energy capacity;

wherein the power sensor is further adapted to detect when the first energy capacity and the second energy capacity fall below the upper threshold and the control device is further adapted to direct the charging circuit to charge the first battery pack to the first maximum energy capacity;

a third battery pack having a third effective energy capacity and a third maximum energy capacity;

wherein the power sensor is further adapted to detect when the first, second, and third energy capacities have fallen below the upper threshold and the control device is further adapted to direct the charging circuit to charge the first battery pack to the first maximum energy capacity; and

a discharge circuit electrically connected to the first, second, and third battery packs and the control device is further adapted to direct the discharge circuit to discharge the first battery pack to the lower threshold before directing the charging circuit to charge the first battery pack to the first maximum energy capacity.

3. A method of charging a backup-battery system, comprising the steps of:

detecting when a first energy capacity of a first battery pack falls below a lower threshold;

comparing the first enemy capacity to a second enemy capacity of a second battery pack;

if the first enemy capacity is less than the second energy capacity, directing a charging circuit to charge the first battery pack to a first maximum energy capacity;

detecting when the first energy capacity and the second energy capacity fall below an upper threshold;

charging the first battery pack to the first maximum energy capacity;

detecting a third energy capacity of a third battery pack;

detecting when any two of the energy capacities have fallen below the upper threshold; and

charging the first battery pack to the first maximum energy capacity; and

discharging the first battery pack to the lower threshold before the step of charging the first battery pack to the first maximum energy capacity.

4. A method of charging a backup-battery system, comprising the steps of:

detecting when a first energy capacity of a first battery pack falls below a lower threshold;

comparing the first energy capacity to a second energy capacity of a second battery pack;

if the first energy capacity is less than the second energy capacity, directing a charging circuit to charge the first battery pack to a first maximum energy capacity;

detecting when the first energy capacity and the second energy capacity fall below an upper threshold;

charging the first battery pack to the first maximum energy capacity; and

discharging the first battery pack to the lower threshold before the step of charging the first battery pack to the first maximum energy capacity.