METHOD AND DEVICE FOR MEASURING INTERNAL RESISTANCE OF BATTERY

• US 20090009134A1
• Filed: 11/07/2007
• Published: 01/08/2009
• Est. Priority Date: 07/06/2007
• Status: Abandoned Application

• Current Assignee: Hong Fu Jin Precision Industry (Shenzhen) Co., Ltd. (Hon Hai Precision Industry Co., Ltd.), Hon Hai Precision Industry Co., Ltd.
• Original Assignee: Hong Fu Jin Precision Industry (Shenzhen) Co., Ltd. (Hon Hai Precision Industry Co., Ltd.), Hon Hai Precision Industry Co., Ltd.
• Inventors: CHUANG, TSUNG-JEN, WONG, SHIH-FANG, ZHANG, JUN-WEI
• Application Number:
  US11/936,762
• Publication Number:
  US 20090009134A1
• Time in Patent Office: Days
• US Class Current: 320/134
• CPC Class Codes: G01R 31/389 Measuring internal impedance, internal conductance or related variables

Abstract

A device for measuring an internal resistance of a battery includes a charging unit, a switch, a measuring unit, and a calculating unit. The charging unit is used for respectively charging the battery through a first resistor (R1) and a second resistor (R2). The switch is used for selectively connecting one of the first resistor and the second resistor to the battery. The measuring unit is used for measuring a first voltage (V1) across the first resistor and a second voltage (V2) across the second resistor. The calculating unit is used for calculating the internal resistance (Resr) via a following formula : Resr=(V2−V1)/(V1/R1-V2/R2). A related method for measuring the internal resistance of the battery is also provided.

Claims

1. A device for measuring an internal resistance of a battery comprising:

a charging unit configured for respectively charging the battery through a first resistor and a second resistor;

a measuring unit configured for measuring a first voltage across the first resistor and a second voltage across the second resistor;

a calculating unit configured for calculating the internal resistance of the battery via the formula;

Resr=(V2−

V1 )/(V1/R1−

V2/R2), wherein, Resr is the internal resistance of the battery, R1 is the resistance of the first resistor, R2 is the resistance of the second resistor, V1 is the first voltage across the first resistor, and V2 is the second voltage across the second resistor.

2. The device as claimed in claim 1, wherein the first resistor has two ends connected to the measuring unit, the second resistor has two ends connected to the measuring unit, and the calculating unit is electrically connected to the measuring unit.

3. The device as claimed in claim 2, further comprising a discharging unit configured for discharging the battery through one of the first resistor and the second resistor;

a second relay configured for selecting one of the charging unit and the discharging unit to be electrically connected to the first resistor and the second resistor;

a controlling unit configured for controlling the switching action of the second switch of the second relay.

4. The device as claimed in claim 3, wherein a common contact of the second relay is connected to the first resistor and the second resistor, a normally closed contact of the second relay is connected to the charging unit, a normally open contact of the second relay is connected to the discharging unit, and an electromagnetic coil of the second relay is connected to the controlling unit.

5. The device as claimed in claim 4, further comprising a comparing unit configured for comparing a terminal voltage of the battery with a predetermined voltage.

6. The device as claimed in claim 5, wherein the comparing unit connects the measuring unit to the controlling unit, the measuring unit measures the terminal voltage of the battery;

if the terminal voltage of the battery is smaller than the predetermined voltage, the second switch of the second relay electrically connects the charging unit to the first resistor and the second resistor.

7. The device as claimed in claim 6, further comprising a first relay configured for selecting one of the first resistor and the second resistor to be electrically connected to the battery.

8. The device as claimed in claim 7, wherein a common contact of the first relay is connected to the battery, a normally closed contact of the first relay is connected to the first resistor, a normally open contact of the first relay is connected to the second resistor, and an electromagnetic coil of the first relay is connected to the controlling unit.

9. The device as claimed in claim 8, wherein the first switch of the first relay electrically connects the first resistor to the battery.

10. The device as claimed in claim 9, wherein the measuring unit is connected to the controlling unit;

when the measuring unit has completed the measurement, the controlling unit controls the first switch of the first relay to electrically connect the second resistor to the battery.

11. The device as claimed in claim 5, wherein if the terminal voltage of the battery is larger than the predetermined voltage, the controlling unit controls the switch of the second relay to electrically connect the discharging unit to the first resistor and second resistor.

12. The device as claimed in claim 11, wherein the switch of the first relay electrically connects the first resistor to the battery.

13. The device as claimed in claim 12, wherein when the measuring unit has completed the measurement, the controlling unit controls the first switch of the first relay to electrically connect the second resistor to the battery.

14. The device as claimed in claim 1, further comprising a display unit configured for displaying the internal resistance of the battery.

15. A method for measuring an internal resistance of a battery, the method comprises the steps of:

measuring a terminal voltage of the battery;

comparing the terminal voltage of the battery with a predetermined voltage;

connecting a charging unit with a first resistor and the battery, charging the battery through the first resistor, and measuring a voltage across the first resistor when the terminal voltage of the battery is smaller than the predetermined voltage;

connecting the charging unit with a second resistor and the battery, charging the battery through the second resistor, and measuring the voltage across the second resistor;

calculating the internal resistance of the battery via a formula;

Resr=(V2−

V1)/(V1/R1−

V2/R2), wherein, Resr is the internal resistance of the battery, R1 is the resistance of the first resistor, R2 is the resistance of the second resistor, V1 is the voltage across the first resistor, and V2 is the voltage across the second resistor;

displaying the internal resistance of the battery.

16. The method as claimed in claim 15, wherein the predetermined voltage is adjustable.

17. A method for measuring an internal resistance of a battery, the method comprises the steps of:

measuring a terminal voltage of the battery;

comparing the terminal voltage of the battery with a predetermined voltage;

connecting the discharging unit with the first resistor and the battery, discharging the battery through the first resistor, and measuring the voltage across the first resistor when the terminal voltage of the battery is larger than the predetermined voltage;

connecting the discharging unit with the battery and the second resistor, discharging the battery through the second resistor, and measuring the voltage across the second resistor;

calculating the internal resistance of the battery via a formula;

Resr=(V2−

V1)/(V1/R1−

V2/R2), wherein, Resr is the internal resistance of the battery, R1 is the resistance of the first resistor, R2 is the resistance of the second resistor, V1 is the voltage across the first resistor, and V2 is the voltage across the second resistor;

displaying the internal resistance of the battery.

18. The method as claimed in claim 17, wherein the predetermined voltage is adjustable.