Part Number: BQ76930
Hello,
I am observing an odd voltage response from cell05 and cell06 relative to the other 8 cells while balancing. This is a 10 cell pack with external balancing. The test I performed was to evaluate the balancing function of the system. I discharged cell10 below the rest of the cells to enter the balancing conditions as set by the host processor.
What is interesting is that during this test cells 1-9 should all be balancing, which they are. But cell05 and cell06 have a odd voltage response to the balancing condition. Below is a picture of a data log that captured this event.
purple line = cell05 voltage
orange line = cell04 voltage
red line = cell05 balance state
yellow line = cell 04 balance state.
Cell04's response to balancing is like the rest of the cells, no voltage oscillation. Cell05, like cell06 seem to oscillate by about 10mV during the balancing routine.
Our host controller requests balancing for 2 seconds. During this time the balancing status bit in the graph is TRUE. When looking at the gate of the external balancing FET with an oscilloscope we can see this 2 second balancing active window, which is chopped up into pulses.
These pulses are the AFE executing the CELLBALLxx command where the total duty cycle devoted to balancing is 70% per 250ms, demonstrated below.
Should I expect the cell05 and cell06 cell voltage to look like choppy like this compared to the other cell voltages during balancing?
