BQ76920: 3 cell configuration

See schematic in original thread. I have shorted cells  at battery connector pins.

Hi,

Have you performed the other suggestions listed in the original thread? 

"You might also measure the voltage across R19 to see if it looks like a normal operating current or a short somewhere on the regulator, probably REGOUT.

In case the part may have been damaged in handling or assembly you might try a different board or part on this board.  If you remove the part check for load on REGOUT with the IC removed."

5s configuration is working fine. So I think this is not an issue of short or disconnect. My doubt is that, shorting connector pins 2,3 and 4 is fine or not?

Hi Shawn ,

I will try that but as per datasheet, we should short vc3-vc4 and vc2-vc3. Is there any problem if I short at battery connector end not at IC end mens shorting before filter resistor and cap from L-R in schematic.

Hi,

Apologies, you should follow the configuration described in Table 24 of the datasheet. Short VC4 to VC3 and VC3 to VC2.

But its not working man thats why I am asking you.

Please reply about position of short IC end or connector end.

Hi Sashi,

Either shorting at the IC or the connector should work fine in this case. I checked your schematic and I cannot find any reason why this should not work. Do you think it is possible the IC has been damaged somehow? Is it still working fine in a 5S configuration?

Can you also send a photo of your connections?

Thanks,

Matt

Hi Matt,

Yes, Its working fine with 5s config. Yeah I will send you the pic.

Thanks

Hi Matt, 

Please find the attached pics.

Thanks,

Sashidrive-download-20201017T072250Z-001.zip

In photo consider,

B- = vc0;

c1 = vc1;

c2,c3,c4 = vc2,vc3 and vc4 respectively

B+ = vc5.

Hi Sashi,

I notice the wires are long from the device before they are shorted at the connectors. Can you try shorting at the device pins or at least on the board connector? The observed voltage difference for the shorted cells needs to be close to zero, so the long wires might result in the device thinking there is a cell present.

Best regards,

Matt

I have tried that by shorting device pins on the board itself but it hasn't work. What I observed the voltage at device pins are vc1=3.556, vc2= vc3=vc4= 7.17, vc5= 10.17. One more observation what I have observed is that while giving 3.3v at ts1 pin for a moment I have tried to measure regout voltage and it goes around some milivolt(100 or something) and becomes zero immediately seems like device goes in ship mode immediately after triggering. Also I have checked all the device pins without battery pack and they are in high impedance state means no short also all the pins are required connections menas no disconnect. If you have any other suggestions or checks please reply.

Hi Sashi,

If the device is not able to boot from Shutdown, it may be damaged. Have you tried replacing the IC on the board?

Matt

Hi Matt,

How can be it possible that the same device is working fine for 5s configuration? One more thing I have to ask that can we configure the device in a way tha every other cell get balanced cmd simultaneously means if  suppose cell 2 has minimum voltage then can we send balance cmd to other cells (cell 1, cell3, cell4 and cell5) simultaneously?

Thanks

Hi Sashi,

It is strange. In your previous thread you said you were having trouble getting the device to boot. Could you still be seeing this issue? The 3 cell configuration should work.

You cannot balance adjacent cells at the same time - this will result in conditions beyond the abs max specs. You can balance every other cell at the same time (odd cells or even cells). See the BQ769x0 Family Top Ten Design Considerations document for more details: https://www.ti.com/lit/an/slua749a/slua749a.pdf

Best regards,

Matt