Figure 1.
The proposed fast charging balancing circuit for LiFePO4 battery.
Figure 1.
The proposed fast charging balancing circuit for LiFePO4 battery.
Figure 2.
The theoretical waveforms in balancing process from VBat1 to VBat8.
Figure 2.
The theoretical waveforms in balancing process from VBat1 to VBat8.
Figure 3.
Mode I, the battery balancing process from higher VBat1 to lower VBat8.
Figure 3.
Mode I, the battery balancing process from higher VBat1 to lower VBat8.
Figure 4.
Mode II, the battery balancing process from higher VBat1 to lower VBat8.
Figure 4.
Mode II, the battery balancing process from higher VBat1 to lower VBat8.
Figure 5.
The theoretical waveforms in balancing process from VBat8 to VBat1.
Figure 5.
The theoretical waveforms in balancing process from VBat8 to VBat1.
Figure 6.
Mode III, the battery balancing process from higher VBat8 to lower VBat1.
Figure 6.
Mode III, the battery balancing process from higher VBat8 to lower VBat1.
Figure 7.
Mode II, the battery balancing process from higher VBat8 to lower VBat1.
Figure 7.
Mode II, the battery balancing process from higher VBat8 to lower VBat1.
Figure 8.
Determine turns ratio by voltage of charging behavior.
Figure 8.
Determine turns ratio by voltage of charging behavior.
Figure 9.
The structure of fast charging balancing circuit.
Figure 9.
The structure of fast charging balancing circuit.
Figure 10.
Flow chart of dynamic battery charging balancing strategy.
Figure 10.
Flow chart of dynamic battery charging balancing strategy.
Figure 11.
The detection of battery voltage circuit.
Figure 11.
The detection of battery voltage circuit.
Figure 12.
Experiment of VGS triggering waveforms for turning on the switch network (VGSodd_0, VGSodd_1, VGSeven_7, VGSeven_8), VGSodd_0, VGSodd_1, VGSeven_7, VGSeven_8: 10 V/div, Time: 20 µs/div.
Figure 12.
Experiment of VGS triggering waveforms for turning on the switch network (VGSodd_0, VGSodd_1, VGSeven_7, VGSeven_8), VGSodd_0, VGSodd_1, VGSeven_7, VGSeven_8: 10 V/div, Time: 20 µs/div.
Figure 13.
Experiment of voltage waveforms of Sa (VGSa, VDSa), VGSa, VDSa: 10 V/div, Time: 20 µs/div.
Figure 13.
Experiment of voltage waveforms of Sa (VGSa, VDSa), VGSa, VDSa: 10 V/div, Time: 20 µs/div.
Figure 14.
Simulation of voltage waveforms of Sa (VGSa, VDSa), VGSa, VDSa: 10 V/div, Time: 20 µs/div.
Figure 14.
Simulation of voltage waveforms of Sa (VGSa, VDSa), VGSa, VDSa: 10 V/div, Time: 20 µs/div.
Figure 15.
Experiment of current waveforms (iNsb, iNpa), iNsb, iNpa: 500 mA/div, Time: 20 µs/div.
Figure 15.
Experiment of current waveforms (iNsb, iNpa), iNsb, iNpa: 500 mA/div, Time: 20 µs/div.
Figure 16.
Simulation of current waveforms (iNsb, iNpa), iNsb, iNpa: 500 mA/div, Time: 20 µs/div.
Figure 16.
Simulation of current waveforms (iNsb, iNpa), iNsb, iNpa: 500 mA/div, Time: 20 µs/div.
Figure 17.
Experiment of VGS triggering waveforms for the switch network (VGSodd_0, VGSodd_1, VGSeven_7, VGSeven_8), VGSodd_0, VGSodd_1, VGSeven_7, VGSeven_8: 10 V/div, Time: 20 µs/div.
Figure 17.
Experiment of VGS triggering waveforms for the switch network (VGSodd_0, VGSodd_1, VGSeven_7, VGSeven_8), VGSodd_0, VGSodd_1, VGSeven_7, VGSeven_8: 10 V/div, Time: 20 µs/div.
Figure 18.
Experiment of voltage waveforms of Sb (VGSb, VDSb), VGSb, VDSb: 10 V/div, Time: 20 µs/div.
Figure 18.
Experiment of voltage waveforms of Sb (VGSb, VDSb), VGSb, VDSb: 10 V/div, Time: 20 µs/div.
Figure 19.
Simulation of voltage waveforms of Sb (VGSb, VDSb), VGSb, VDSb: 10 V/div, Time: 20 µs/div.
Figure 19.
Simulation of voltage waveforms of Sb (VGSb, VDSb), VGSb, VDSb: 10 V/div, Time: 20 µs/div.
Figure 20.
Experiment of current waveforms (iNsa, iNpb), iNsa, iNpb: 500 mA/div, Time: 20 µs/div.
Figure 20.
Experiment of current waveforms (iNsa, iNpb), iNsa, iNpb: 500 mA/div, Time: 20 µs/div.
Figure 21.
Simulation of current waveforms (iNsa, iNpb), iNsa, iNpb: 500 mA/div, Time: 20 µs/div.
Figure 21.
Simulation of current waveforms (iNsa, iNpb), iNsa, iNpb: 500 mA/div, Time: 20 µs/div.
Figure 22.
Battery’s voltage curve during fast charging balancing process.
Figure 22.
Battery’s voltage curve during fast charging balancing process.
Table 1.
Experimental design parameters.
Table 1.
Experimental design parameters.
Design Parameters | Value |
---|
Switching Frequency fs | 20 kHz |
Duty Cycle D | 45% |
Turns Ratio Npa: Npb: Nsa: Nsb | 1: 1: 1.2: 1.2 |
Filtering Capacitance Cπ1, Cπ2, Cπ3, Cπ4 | 100 µF |
Filtering Inductance Lπ1, Lπ2 | 33 µH |
Table 2.
Specification of cell, (Company: A123 System LiFePO4 ).
Table 2.
Specification of cell, (Company: A123 System LiFePO4 ).
Model Number | ANR26650M1B |
---|
Charging Voltage | 3.6 V |
Nominal Voltage | 3.3 V |
Nominal Capacity | 2.5 Ah |
Operating Temperature | −30 °C~55 °C |
Storage Temperature | −40 °C ~60 °C |
Table 3.
Open loop voltage for discharged cells in the test battery string.
Table 3.
Open loop voltage for discharged cells in the test battery string.
Cell Number | Open Loop Voltage (V) |
---|
VBat1,(Cell1) | 2.623 |
VBat2,(Cell2) | 2.616 |
VBat3,(Cell3) | 2.592 |
VBat4,(Cell4) | 2.602 |
VBat5,(Cell5) | 2.611 |
VBat6,(Cell6) | 2.625 |
VBat7,(Cell7) | 2.634 |
VBat8,(Cell8) | 2.639 |
Table 4.
Balancing time and energy loss in each interval.
Table 4.
Balancing time and energy loss in each interval.
Balancing Interval | Balancing Time (sec.) | Energy Losses (J) |
---|
I | 124 | 27.42 |
II | 179 | 42.94 |
III | 178 | 42.697 |
IV | 90 | 22.012 |
V | 31 | 6.989 |
VI | 88 | 11.391 |
VII | 40 | 9.395 |
Table 5.
Measurement of battery balancing process.
Table 5.
Measurement of battery balancing process.
△V1 = 0.03 V (from I–V), △V2 = 0.02 V(from V–II) | Value |
---|
Total balancing time (sec.) | 730 |
Charging time (sec.) | 4250 |
Total energy loss (J) | 162.844 |
Average efficiency of the converter (%) | 79.8 |
Maximum differential voltage (V) | 0.018 |
Table 6.
Comparison of different single △V for a complete balancing process.
Table 6.
Comparison of different single △V for a complete balancing process.
△V (V) | Total Balancing Time (sec.) | Maximum Differential Voltage (V) |
---|
0.02 | 2695 | 0.014 |
0.03 | 411 | 0.023 |
0.04 | 365 | 0.038 |
0.05 | 315 | 0.061 |