Hello,
in our application we have a 144s2p battery which is diveded in two seperate 72s2p stacks which are connected in series. Each stack is supervised by 12 bq76pl536A-Q1 (So one BQ76 supervises one 6s2p configuration). The two bottom BQ76´s are both connected to a single µC via one digital Isolator ISO7241C per BQ76 (as shown in the document "slua562 Improving Communications with the bq76PL536"). After the digital isolator we convert the four SPI-Host-Signals (SCLK, CS, SDO,SDI) via RS485-drivers (Adm485arz) in a differential signal. Both 72s2p stack use the same SCLK, SDI, SDO. Only the CS is separate for each stack. We have put a system overview of our configuration in the attachment.
When no current is drawn from the battery, we can perfectly read out all cell voltages and temperatures. Communication with the 24 BQ76 works fine. But as soon as we turn on our power electronics / motor controller which controls a permanent magnet synchronous motor nearly all communication fails and we have extremely heavy noise on the data lines (especially SDO) from both bottom-BQ76. The motor controller works with a switching frequency of 16kHz, and the noise on the SDO-Line is also periodic with this frequency, so there seems to be a coincidence. But we can´t figure out how the switching frequency of the motor controller can affect the BQ76. Have you ever had similar experience with such problems or any idea what the cause of these problems could be? If you need further information from us, we can send it to you via private message.
Thanks in advance
B.Spatafora
