Charge control circuit for a battery

• US 6,759,829 B2
• Filed: 09/13/2002
• Issued: 07/06/2004
• Est. Priority Date: 09/13/2002
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Becker-Irvin, Craig H.
• Primary Examiner(s): Tibbits, Pia
• Application Number:
  US10/242,982
• Publication Number:
  US 20040051505A1
• Time in Patent Office: 662 Days
• Field of Search: 320/26, 320/21, 320/101, 320/128, 320/143, 320/134, 320/137, 320/165, 702/63, 702/130, 324/427, 324/431, 340/636.12, 340/636.15
• US Class Current: 320/128
• CPC Class Codes: H02J 7/00714 in response to battery charging or discharging current
• CPC Class Codes: H02J 7/007182 in response to battery voltage

Abstract

A charging circuit (28) particularly suited for use in a satellite (20) has a battery cell (32). A voltage sensor (36) is coupled to the battery for generating a cell voltage signal. A current sensor (34) is coupled to the battery cell (32) and generates a cell charge current signal. A controller (38) is coupled to the voltage sensor (36) and the current sensor (34). The controller (38) determines a compensated voltage in response to the cell voltage signal and the charge current signal and controls the charging of the battery cell (32) in response to the compensated voltage.

Claims

1. A charging circuit for a battery comprising:

a voltage sensor coupled to the battery for generating a cell voltage signal;

a current sensor coupled to the battery for generating a cell charge current signal; and

a controller coupled to said voltage sensor and said current sensor, said controller determining a compensated battery cell voltage in response to the cell voltage signals direct current resistance of the cell, and the charge current signal, said controller charging the battery when the compensated voltage signal is below a voltage threshold.

2. A charging circuit as recited in claim 1 wherein the compensated battery cell voltage is determined in response to harness resistance.

3. A charging circuit as recited in claim 1 wherein the threshold is reprogrammable.

4. A charging circuit as recited in claim 1 wherein the battery comprises a lithium ion battery.

5. A charging circuit as recited in claim 1 wherein the compensated battery cell voltage is determined by V_measured−

I_cell×

R_cell+V_o where V_measured is the cell voltage signal, R_cell, is the direct current resistance, I_cell is the cell charge current signal and V_o is an offset voltage.

6. A satellite comprising:

a battery;

a charging circuit coupled to the battery;

a voltage sensor coupled to the battery for generating a cell voltage signal;

a current sensor coupled to the battery for generating a cell charge current signal; and

a controller coupled to said voltage sensor and said current sensor, said controller determining a compensated battery cell voltage in response to the cell voltage signal, direct current resistance of the cell, and the charge current signal, said controller charging the battery when the compensated voltage signal is below a voltage threshold.

7. A satellite as recited in claim 6 wherein said battery comprises a lithium ion battery.

8. A satellite as recited in claim 6 wherein the compensated battery cell voltage is determined by the formula $\mathrm{Vcompensated}=\frac{\mathrm{Vmeasured}-\mathrm{Ibatt}}{}$

 

×

RtotalNcells+Vo

where V_measured is the measured cell voltage signal,

Ibatt is the measured battery charge current in amperes,

Rtotal is a characterized DC resistance of the total battery and a harness,

Ncells is a number of series connected battery cells, and

Vo is an arbitrary offset voltage.

9. A satellite as recited in claim 8 wherein the arbitrary offset voltage is zero.

10. A satellite as recited in claim 6 wherein said battery comprises a plurality of cells.

11. A satellite as recited in claim 6, wherein the compensated battery cell voltage is determined in response to harness resistance.

12. A satellite as recited in claim 6 wherein the threshold is reprogrammable.

13. A satellite as recited in claim 7 wherein said controller comprises a voltage processor and a battery charge unit.

14. A method for charging a battery comprises:

measuring a cell voltage;

measuring a cell charge current;

determining a compensated voltage in response to the cell voltage, the direct current cell resistance, and the cell charge current;

comparing the compensated voltage to a threshold; and

discontinuing the cell charge current when the compensated voltage exceeds the threshold.

15. A method as recited in claim 14 wherein said battery comprises a lithium ion battery.

16. A method as recited in claim 14 wherein said threshold is reprogrammable.