Hi team,
Here's an issue from the customer may need your help:
Use the gauge to do a 4-string protection board. Shorted 4 and 5 strings. When power is applied, the alert pin reports an undervoltage error. But the voltage capture shows that all four strings of voltage are good.
The 4-string software logic is the same as the 5-string (just the fifth one is not captured). What else does the software need to do?
Could you help check this case? Thanks.
Best Regards,
Cherry
Hi Andria,
Thanks for your support.
Could you please send me the portion of your customer's schematic that shows how they connected their cells to the BQ76920?
Additionally--just to clarify--are you saying that an external voltage capture with a multimeter shows okay cell voltages, or that the BQ76920 itself is reporting back to the customer that the voltages are okay, then the alert pin is reporting the undervoltage?
Voltmeter measures all four cell voltages are normal, and BQ76920 reports the same voltage as the cell voltages measured by the multimeter.
In the above scenario, the alert pin reports an undervoltage whenever the battery is plugged into a custom board. The software will clear the undervoltage logic periodically. When cleared, the alert pin reports an undervoltage again.
The following is the register status information for the AFE detected by the PC: You can see that UV is now undervoltage, and the unit "undervoltage _ hard drive"(it's 单体欠压_硬 in red) is the AFE hardware undervoltage reported by alert:
In addition, the customer uses 920 for 4-string protection board, but the 920 is normally 5-string. Hardware shorting BC5 directly to BC4. Customers have the following questions about this:
a) What does the software need to do when changing from 5 to 4 strings? Is BC5 less collected for 4 strings than 5 strings?
b) This UV is the undervoltage reported by the AFE chip. Which string of undervoltage is there?
Thanks and regards,
Cherry
