Device for managing battery packs by selectively monitoring and assessing the operative capacity of the battery modules in the pack

• US 6,239,579 B1
• Filed: 07/03/1997
• Issued: 05/29/2001
• Est. Priority Date: 07/05/1996
• Status: Expired due to Term

• Current Assignee: Estco Battery Management Incorporated
• Original Assignee: Estco Battery Management Incorporated
• Inventors: Dunn, James H., de Oliveira, Julio C., Gerwing, David H.
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): Toatley, Gregory J.
• Application Number:
  US08/887,844
• Time in Patent Office: 1,426 Days
• Field of Search: 320/121, 320/119, 320/126, 320/128, 324/426
• US Class Current: 320/121
• CPC Class Codes: G01R 31/392 Determining battery ageing or deterioration, e.g. state of health
• CPC Class Codes: G01R 31/396 Acquisition or processing of data for testing or for monitoring individual cells or groups of cells within a battery
• CPC Class Codes: H02J 7/0013 acting upon several batteries simultaneously or sequentially H02J7/1423 takes precedence
• CPC Class Codes: H02J 7/0019 using switched or multiplexed charge circuits
• CPC Class Codes: H02J 7/0047 with monitoring or indicating devices or circuits
• CPC Class Codes: H02J 7/005 Detection of state of health [SOH]
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries

Abstract

The invention relates to a device for managing battery packs by measuring and monitoring the operating capacity of individual battery modules in a battery pack. A programmable logic controller directs the selective closing of relays to allow individual battery modules to be load-tested using a variable discharge load unit, without compromising useful battery pack capacity. A battery module whose useful capacity falls below a predefined threshold may be connected to a battery charger for replenishment and then electrically realigned with the remaining modules in the pack for continued operation. Alternatively, an alarm may be triggered which alerts the user that the module is due for replacement. This sequence of events is performed on all cells in the pack at a predetermined interval.

Claims

1. A system for directly assessing and controlling the useful capacity of an online battery pack, comprising:

a programmable logic controller operatively connected to a monitor circuit and to one or more battery modules comprising said battery pack, said monitor circuit comprising battery module variable charging means, and variable discharge load means;

wherein said programmable logic controller selectively and sequentially opens and closes a plurality of relays which connect with said variable charging means and said variable discharge load means to alternatively define a discharge circuit which enables one of said modules to be variably discharged by said variable discharge load means under a predefined variable load wherein the useful capacity is calculated from a time and current required to discharge said module under said predefined variable load by said programmable logic controller.

2. A system as claimed in claim 1, further comprising means for recording of said data calculated by said programmable logic controller.

3. The system as claimed in claim 1 or 2 wherein said relays are selected from the group consisting of multi-pole relays, contactors or solid state switching devices.

5. The device of claim 3 wherein said relays are selected from the group consisting of multi-pole relays, contactors or solid state switching devices.

4. A device for directly assessing the useful capacity of at least one battery module within a battery pack, comprising:

a programmable logic controller operatively connected to a plurality of battery modules comprising a battery pack, variable battery module charging means, and variable battery load means;

wherein each of said modules may be selectively isolated from the other said modules defining said battery pack, by the opening and closing of relays which connect said modules with said variable discharge load means and said battery module variable charging means, enabling a sequential and selective discharging of said modules to a selectable cut-off voltage level by said variable discharge load means along with a measurement of a time required to discharge said modules to a selectable cut-off voltage level and further enabling a subsequent recharging of said modules to a selectable recharge voltage level by said variable battery module charging means.

6. The device as claimed in claim 4 wherein said device is integral with said battery pack.

7. A method of sequentially assessing the useful capacity of a plurality of battery modules which define a battery pack, which comprises the steps of:

selecting one of said modules for assessment;

connecting said selected module to a variable discharge load means by closing relays which connect said module to said variable discharge load means;

measuring a time to discharge said module to a predetermined cut-off voltage level under the specific load which defines the useful capacity of said module, while said module is under the specific load;

determining whether said useful capacity meets a predefined threshold for useful capacity;

disconnecting said selecting module from said variable discharge load by means of opening said relays and either;

recharging said selected module by connecting said selected module to a variable battery charger where said useful capacity meets said predefined threshold;

or generating a signal where said useful capacity does not meet said predefined threshold;

wherein the above steps are coordinated by a programmable logic controller operatively comprising;

in combination,

at least one voltage reader;

at least one battery current reader;

at least one module current reader; and

a switch controller to control the opening and closing of said relays.

8. A method as claimed in claim 7 wherein said selected module is reinserted into the circuit which defines said battery pack by reconnecting said selected module to said plurality of modules by the selective opening and closing of relays which connect said modules with said battery charger, and said variable discharge load, following said recharging.

9. A method as claimed in claim 7 wherein an extra module is added to said battery pack to power said battery pack charger when said battery pack charger fails while selected module is discharged.

10. A method as claimed in claim 7 further including the step of using an optimal recharge method on said selected module, said optimal recharge method being determined by a state of charge of other modules.

11. A device for cycling batteries while the battery remains in service, comprising:

a programmable logic controller operatively connected to a management and control circuit and to a battery module within a battery pack, said monitor circuit comprising variable battery module charging means, and variable discharge load means;

wherein said programmable logic controller selectively and sequentially opens and closes a plurality of relays which connect with said variable charging means and said variable discharge load means to alternately define a discharge circuit enabling said module to be discharged by said discharge load means under a predefined load and enabling a measurement and calculation by the controller of discharge time and current required to discharge said module.