bq20z75 Problem Setting Cell Chemistry

Order is important here,  try loading the senc file, close and restart the EVSW, update the CHEM ID and then once the CHEM ID is programmed,  program your gg file.

I didn't do it in that order, I sent the 08 command to get it out of ROM mode, exited/restarted the software then loaded the gg file. Then I tried to change the chemistry.

Your post didn't mention when to give it the 08 command. When should that happen?

Also, I now have a VSHUT flag being set and I can't get it to clear. Have I trashed this pack?

you can send 08 command as you do before you restart EVSW, but must reverse order of loading gg file and changing Chem IID so that CHEM ID is changed once EVSW restarted and you program GG file last after choosing chem ID.

Can I reload the senc file when there's a PF flag set?

you have tripped a permanent fail which you can clear by sending 2673 1712 as a 2 word manufacturer access command . Until you clear this, the pack is shutdown

Search 'permanent fail clear (PFkey)'  in technical reference manual

No, send the two word command 2673 1712 to clear the PF.

Not working.

make sure to enter the 2673 1712 words simultaneously using the "write two word command"  button on the evsw sbs screen and not sequentially in the mac access field

That's something I DID know (I'm saying this in a good voice)

That is something I send to SMBus command 00, right?

check to make sure the condition causing the VSHUT flag and permanent fail have been removed or else it will just retrip

yes

I saw that in another post and this isn't making sense to me. (Not the part about making sure to eliminate what caused the error) There shouldn't be an error. I charged the pack to full at an acceptable charge rate. It rested for 2 hours. I discharged it at an acceptable rate down to just below Term Voltage then let it rest for more than 5 hours. The SBS screen looked perfect, everything I would have expected. The cells were both (Pack is 2S1P) a little over 3.3V. Both FETs were on.

I downloaded the gg file. Opened it up in Notepad, changed Update Status to 02, Cycle Count to 0. Programmed the pack with the senc file, did a 08 command. Restarted the EV software, programmed the gg file then went to check the chemistry. Tried to program it with the right chemistry and got the errors. Now I see CUV, OTD in Safety Status and VSHUT in PF Status.

There shouldn't be errors. The calibration information should have been in the gg file so I wouldn't have changed the calibration settings. In fact, they would have been lost when I loaded the senc file and should have been replaced with good values when I dropped the gg file back on it.

in your second paragraph you still seem to be programming the chemistry after the GG file. You need to program chemistry before the GG file.

I understand that but I can't even get back to that stage.

The point I was making is that I have a VSHUT error when I haven't done anything that should have created one.

Have I trashed the pack?

What are the current cell/pack voltage compare to the undervoltage thresholds?

You should be able to clear the fault but it is possible that the battery vaoltage has now just got so low compared to any settings you set in the electronics that it is somehow it is just immediately retripping when you program the senc. Can you try and independently charge the pack back up without the 20z part in the circuit, then reconnect the electronics and try to follow the remaning steps we discussed ? 

I can't get to the cells, the pack is sealed. I did find that the ConfigA register has CC0 and CC1 both set, for a 4S pack. I tried to change it to 0121, the value I want, but it wouldn't take the change.

One more thing I'm seeing, the temperature reported on the SBS screen is 128°C. I go to the Calibration screen, select the Internal temperature sensor and uncheck the Ext Sensor boxes. I enter 22 in the box and click on the Calibrate Part as indicated Below button. The Measured Temperature drops to 19.8 for 1 second then jumps back up to 128.

When you say the pack is sealed I assume you only mean physically but it does prompt the question what is the status of the FAS and SS bit in the operation status registers, these are bits 6 and 5 of the high byte and will be red on the SBS screen if set. If these are set then that may be what is stopping you load a senc file,  modify data flash, clear your PF fault . If these bits are set you must send codes to reset them.

See SLUA421 figure 26 and figure 28 which shows the codes to be sent . 

After these bits have been set once then every time after you restart the EVSW you will need to reset these bits again unless you reload a default original file to return the part to original state.

I shouldn't have used that word. The bq is NOT sealed. The cells are in a plastic enclosure that is glued.

Still a good idea to check the FAS and SS bits are off.

The bits are not set. They are green on the SBS page.

Did you manage to solve your issues?