BQ78350-R1: cell voltage fluctuation on cell 6 and cell 10

Hi Steve,

This is not normal. Can you share your schematic and we can help review for any issues. Additionally, you can view this video that walks through the schematic creation process to help avoid common issues: https://www.youtube.com/watch?v=B5dsIc2C_xA 

Best regards,

Matt

Where should I upload / send my schematics?

Hi Steve,

I sent you an E2E friend request. You should be able to send me your schematic through a private message.

Thanks,

Matt

Thank you Matt. I'll add those resistors to my design. Any particular reason the resistors on VCX5 and VCX10 should match the one on BAT to cell 15? It looks like the reference design uses 100 ohms on the BAT, and 1K on the other 2.

Matt, Another question. Can we power REGSRC from a 5V supply which is powered by either the battery, or the charger if the charger is plugged in? The problem is that if the batteries deep discharge due to leakage current and long term shelf storage, the shunt regulator in the reference design can't function. If the pack voltage drops below 14V the system gets into an unrecoverable state. The BMS has no power so it  can  not enable the charge FET's. By powering REGSRC with a 5V power supply that can be powered by either the charger or the batteries, we should be able to recover from accidental deep discharge because the BMS will get power when the charger is plugged in. Do you see any problem with this approach?

Thanks,

Steve  

Hi Steve,

I think this should be okay. Although, 5V may be low during normal operation (when powered by the battery). There are two figures (Figure 12 and Figure 15) in the Top Design Considerations app note that show the FET voltage vs REGSRC voltage: http://www.ti.com/lit/an/slua749a/slua749a.pdf

Matt

Matt, I'm using the BQ76200 high side driver to control the FET's. It only requires 1.2V for a logic high so 5V into REGSRC should fine. Do you agree?

Thanks,

Steve