Secondary battery system

• US 8,994,322 B2
• Filed: 06/28/2012
• Issued: 03/31/2015
• Est. Priority Date: 06/29/2011
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Yamamoto, Tsunenori, Sasaki, Hironori
• Primary Examiner(s): Kik, Phallaka
• Application Number:
  US13/535,410
• Publication Number:
  US 20130002194A1
• Time in Patent Office: 1,006 Days
• Field of Search: 320/107, 320/128, 320/132, 320/153, 323/353, 323/371
• US Class Current: 320/107
• CPC Class Codes: H01M 10/425 Structural combination with electronic components, e.g. electronic circuits integrated to the outside of the casing printed circuits H05K1/00
• CPC Class Codes: H01M 10/4257 Smart batteries, e.g. electronic circuits inside the housing of the cells or batteries
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: H01M 10/443 in response to temperature
• CPC Class Codes: H01M 10/48 Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte constructional details of current conducting connections for detecting conditions inside cells or batteries, e.g. details of voltage sensing terminals, H01M50/569
• CPC Class Codes: H01M 10/486 for measuring temperature
• CPC Class Codes: H02J 7/00 Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

Since in existent charge-discharge control the battery direct current resistance of a lithium ion battery increases at a low temperature or in a low SOC, the battery voltage may possibly exceed greatly the maximum allowable voltage instantaneously due to over-voltage during charging or may possibly decrease greatly to less than the minimum allowable voltage during discharging. If the lithium ion battery continuously lies in such a state the battery performance is degraded abruptly.

The battery resistance of a lithium ion battery module is estimated in accordance with SOC and temperature of the lithium ion battery module, and current to charge is set properly based on the estimated battery resistance.

Claims

1. A secondary battery system comprising:

a battery module having at least one lithium ion battery;

a measuring device for measuring a voltage and a temperature of the battery module;

a state of charge detection device for detecting a state of charge based on the voltage; and

a charge-discharge control device;

wherein an estimated battery resistance of the battery module, corresponding to the state of charge and the temperature of the battery module, is calculated by the charge-discharge control device based on a standard battery resistance, a standard initial battery resistance, and a measured initial battery resistance;

the standard battery resistance is calculated based on a standard operating condition of the battery module;

the standard initial battery resistance is calculated based on a standard initial condition of the battery module;

the measured initial battery resistance is calculated based on a measured initial condition of the battery module; and

the charge-discharge control device calculates the estimated battery resistance using a formula R=[(R′

×

R0)/R0′

];

wherein R is the estimated battery resistance, R′

is the standard battery resistance, R0′

is the standard initial battery resistance, and R0 is the measured initial battery resistance.

2. The secondary battery system of claim 1, wherein

the standard battery resistance is calculated based on a voltage and a current through the battery module during the standard operating condition.

3. The secondary battery system of claim 2, wherein

the standard initial battery resistance and the measured initial battery resistance are determined based on data stored in a storage device,

wherein the data include the voltage and the temperature.

4. The secondary battery system of claim 3, wherein

the charge-discharge control device sets a current to supply to the battery module based on the estimated battery resistance.

5. The secondary battery system of claim 4, wherein

the charge-discharge control device stops supplying the current to the battery module if the voltage exceeds a predetermined value.

6. The secondary battery system of claim 5, wherein

the charge-discharge control device reinitiates the current supplied to the battery module, when the state of charge is less than or equal to a threshold value.

7. The secondary battery system of claim 6, wherein

the estimated battery resistance is updated when the charge-discharge control device reinitiates the current supplied to the battery module.

8. The secondary battery system of claim 1, wherein

the standard operating condition is a condition in which the battery module does not degrade excessively.

9. An control method for a secondary battery system with a battery module having at least one lithium ion battery, comprising:

measuring a voltage and a temperature of the battery module;

detecting a state of charge based on the voltage;

calculating, by a control device, an estimated battery resistance of the battery module, corresponding to the state of charge and the temperature of the battery module, based on a standard battery resistance, a standard initial battery resistance, and a measured initial battery resistance; and

controlling, by the control device, a charge current for charging the battery module based on the estimated battery resistance;

wherein

the standard battery resistance is calculated based on a standard operating condition of the battery module;

the standard initial battery resistance is calculated based on a standard initial condition of the battery module;

the measured initial battery resistance is calculated based on a measured initial condition of the battery module; and

the charge-discharge control device calculates the estimated battery resistance using a formula R=[(R′

×

R0)/R0′

];

wherein R is the estimated battery resistance, R′

is the standard battery resistance, R0′

is the standard initial battery resistance, and R0 is the measured initial battery resistance.