SLUUBT5C November 2018 – June 2021 BQ40Z80
The device can natively support pack capacities up to 29 000 mAh and battery currents up to 32 767 mA. Current scaling is required to support higher capacities and currents. To support large battery configurations where current can exceed 32767 mA, the current data can be scaled to ensure accurate reporting through the SMBus. The data reported is scaled based on the setting of the Scale Factor. The value of Scale Factor can be set between 0–100. Setting 0 (default) disables the scaling. Scale Factor should be selected based on the battery size and current magnitudes expected. The Scale Factor should be calculated for both parameters and the largest scale factor should be used to meet both requirements.
First, the data flash configuration must scale the capacity to ensure that the maximum capacity does not exceed 29 000 mAh. As an example, if the maximum pack capacity is 100 Ah, then the Scale Factor is set to 100 000 mAh / 29 000 mAh = 3.45x or rounded up to 4x. The DesignCapacity mAh and Design Capacity cWh must be scaled in data flash, and all current and capacity parameters in the data flash are divided by 4x.
Second, the data flash configuration must consider scaling the current to ensure that the maximum current does not exceed 32 767 mA. As an example, if the maximum discharge current is 64 A, then the Scale Factor is set to 64 000 mA / 32 767 mA = 1.95x or is rounded up to 2x. To ensure accurate current measurement, the input voltage generated across the current-sense resistor should not exceed ±100 mV. The value of the sense resistor must be set to ensure that this voltage is not exceeded at the maximum charge and discharge current. The current calibration is automatically adjusted based on the Scale Factor during the calibration phase. For example, if a 4 A discharge current is used to calibrate the pack, then –4000 mA is entered as the actual current, so this value does not need to be scaled.
Finally, the larger of the two calculated Scale Factors should be used. When considering both examples, where the capacity resulted in a Scale Factor of 4, and the current resulted in a Scale Factor of 2, the Scale Factor of 4 should be used. All current and capacity parameters entered into data flash should be divided by 4 if Scale Factor is set to 4, and the host must multiply these parameters by the Scale Factor to calculate the true value.
The MAC command CurrentLong() (0x0082) is provided to report current greater than 32767 mA in mA resolution. All other currents and capacities are reported as scaled values, and the host must multiply the value by the Scale Factor. All protections must also be divided by the Scale Factor