FRDM33771(2)BSPIEVB current measurement enablement in MC3377x EvalGUI with a BATT-14AAAPACK and load resistor in BATT-14AAAPACK

Document created by Jozef Kozon Employee on Dec 4, 2019Last modified by Tomas Vaverka on Dec 4, 2019
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The FRDM33772BSPIEVB serves as a 6-channel and FRDM33771BSPIVB as a 14 channel battery cell controller with a passive cell balancing. A FRDM-KL25Z evaluation board is used for communication with FRDM3377xBSPIEVB and a computer through SPI interface. The kit together with BATT-6EMULATOR 6-cell battery emulator  for the FRDM33772BSPIEVB and BATT-14EMULATOR 14-cell battery emulator for FRDM33771BSPIVB or a battery pack BATT-14AAAPACK for either of them is dedicated to support customer development and evaluation. For a status reading and settings an MC3377x EvalGUI is used.

Figure 1. FRDM33771SPI evaluation board

Figure 1. FRDM33771SPI evaluation board

Figure 2. BATT-14AAAPACK battery pack

Figure 3. BATT-14EMULATOR to supply MC33771 EVBs

 

MC3377x EvalGUI

The Graphic User Interface MC3377x EvalGUI is intended to use for evaluation of MC3377x cell controllers.

Figure 4. MC3377x Evaluation GUI version 4.02

Hardware setup

The GUI supports two types of BMS architectures. Central, only one cluster and distributed, up to 15 clusters. For the central BMS architecture an MC33771 EVB or MC33772 EVB must be stacked on top of an FRDM-KL25Z board. One of the battery emulators or the battery pack is connected through a 34-pin cells connector. For the distributed BMS architecture a MC33664 evaluation board stacked on top of a FRDM-KL25Z is used. The MC3377x evaluation boards are connected to the MC33664 EVB through a twisted pair TPL bus. Connection to a computer is made through OpenSDA port on FRDM-KL25Z and USB on the computer side.

Figure 5. FRDM-33771SPIEVB stacked on top of FRDM-KL25Z and BATT-14AAAPACK connected as central BMS architecture

 

After hardware setup is done start the MC3377x EvalGUI and follow instructions for Initial Configuration in MC33771/772 Evaluation GUI Documentation. For access click info->Open docu in MC33771/772 Evaluation GUI.

Figure 6. Access to MC33771/772 Evaluation GUI document

 

When the initial configuration is done, voltage reading of every battery cell and overall voltage of all connected batteries in series is enabled. However current measurement is disabled by default.

Figure 7. Battery cells measurement with current measurement disabled

 

Enablement of current measurement is done in Cluster view by setting a Bit9 (IMeasEn) in in SYS_CFG1 register to logic 1. The field changes from dark green to  light green and the current measurement is enabled.

Figure 8. Enablement of the current measurement

Figure 9. Current measurement enabled

 

Current in the GUI is displayed in mV and for the current consumption has to be calculated. Because shunt resistor is Rshunt=100mΩ and measured voltage 1.243mV, thus for this case the current consumption is I=Ushunt/Rshunt = 12.43mA. The shunt resistor has to be chosen so the voltage doesn’t exceed +/-150mV. The voltage is sensed on SENSE_P and SENSE_N pins of the MC3377x controller.

Figure 10. Shunt resistor R1 on the BATT-14AAAPACK

It’s also possible to use a resistor in the battery pack as a load. The resistor is not populated. Recommended value is 1kΩ, 3W , SMT 2512. The resistor can be connected and disconnected with SW3 switch.

Figure 11. Recommended load resistor R7 and toggle switch SW3

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