AN2309
Cell-Balancing Parameters
All cell-balancing parameters are located in the header file globdefs.h in the project folder. The header file globdefs.h contains the following parameters:
Table 3. Cell-Balancing Parameters
Parameter | Unit | Description |
Vmeas_err | V | Resistor Matrix Error for Measuring Cell Voltage |
| | |
Vin_err | V | Internal Cell Impedance Error |
| | |
Vch_bal_min | V | Minimum Cell Balance for Charge Phase |
| | |
Vdisch_bal_min | V | Minimum Cell Balance for Discharge Phase |
| | |
Vdisch_mid | V | Voltage of 50 Percent Charging Cell During Discharge Phase |
| | |
Ibal_min | A | Minimum Charge Current Value When the Cell Balancing is Allowed (on |
| | CV Phase) |
| | |
T_BAL_INTERVAL | second | Cell-Balancing Interval |
| | |
Conclusion
A two-cell battery charger with cell-balancing technology has been described. Recommendations for cell-balancing circuit components are given. An effective cell-balancing algorithm for both charge and discharge phases is developed. The algorithm avoids problems that can arise in a battery pack with two cells in series. By altering several configuration parameters, the cell-balancing algorithm can easily be adapted for various applications and selected batteries. A method to perform cell balancing is proposed that uses charge/discharge phases that do not significantly lengthen charge times. This two-cell battery charger supports the pulse charge technique.
The two-cell battery charger algorithm and cell-balancing algorithm are implemented in the PSoC device firmware. The dedicated PC-based software is developed to perform real-time charging and cell-balancing process visualization and analysis through a graphical user interface. The proposed device can be used as a complete battery pack management system for laptop computers, and medical, industrial, and other applications. References have been made to AN2294 if users are interested in easily adding fuel gauge functionality to this project. The unique architecture of the PSoC device and the in-circuit and self-programming capabilities make these operations simple. The chosen CY8C24x23A PSoC device family further reduces total system cost.
Figure 12. Two-Cell Battery Charger Photograph, Actual Size
November 25, 2007 | Document No. 001-17394 Rev. *B | - 17 - |
