Need help generating a golden image with a BQ20z75

Hi Marc

• we always recommend turning on logging every few seconds  and auto export gg files at regular intervals ( say 10 minutes) during the learning cycles as it helps debugging when things don't happen as planned
• a good app note to follow is  6507.slua334b preparing optimised default flash constants for specific battery types.pdf , top of page 2 the procedure for when no close QMAX is known.This procedure always starts the learning ( effectively when  0x21 to turn on IT is sent) with a charge cycle. It is not completely clear to me if you started with a discharge after sending 21 or a charge
• What is you design capacity, you need a min C/10 discharge rateto update Ra Tables during discharge, and I would recommend a similar min C/10 during charging
• Did you see update status change at all , ie did you see 05 ?
• I have been recommended not to use the learning cycle facility on bqEasy with a FET to turn on off charging and discharging and to control the phases manually which is what I do during my learning cycles. It is fine to use bqEasy to do the FLASH configuration but do the actual learning cycle control yourself manually.
• Assuming that the CHEM ID 0232 is correct for your cell,  and looking at the selection table it does appear to be, then with that all said, in your particular case what I think might be causing your problem is the fact you lowered the charge voltage to 8.2V ( = 4.1V/cell).  On the first charge cycle to get a QMAX update the gauge wants to see 90% passed charge. Based on the CHEM ID data on that very first cycle to learn QMAX the gauge needs to see the cells taken to 4.2v in order to realise that 90% passed charge. Once you have done the first charge and discharge cycle and seen update status go to 06 you can then reduce your charging voltage and charge termination voltage to 8.2V ( 4.1V) and the gauge will re-optimise FCC ( full charge capacity) for that setting. On that very first charge cycle if you cannot change the charger output to 8.4V I would recommend doing the charging with a power supply which has a current limit, setting the voltage to 8.4V and using the power supply current limit to control the charging current. Check the battery datasheet to check what taper current to terminate charge at as well in order to get the specified capacity.

Hi Mike,

Thanks for your prompt answer,

I have made a charge using a lab source at 8.4V last Friday and this morning The QMAX parameters seem to have been updated, Cell0 R_a flag and Cell1 R_a flag are nom 0x0055 and update status have changed from 4 to E. What does the E value for Update Status mean? I expected it to change to 6.

Bests regards,

Marc

Hi Marc,

0E is okay and  the valid final state that was added to latest firmware release which just reflects that part recieved another QMAX update with FC set , see descriptions below that I cut from the 20z65 TRM where it was better documented.  You got this as you did another optimize/check  cycle which is fine. When you export your golden file you should still set update status to 02 and then when you create more packs using your golden image the   02 will become 06 when you send the enable IT command to those packs and then after they cycled getting a so called 'Field QMAX Update' then update status will again set to 0E on those packs

Mike

Hi Mike,

I was able to generate a .dfi file.

Now I want to test it in a fresh battery.

I used bqeasy setup screen to program the previously generated .dfi file and it work!

After, documentation say : 'Go to the SBS screen. enter a 41 in the Manufacturer Access field and press Enter on the computer to initialize the RAM. Enter a 21 into the Manufacturer Access field and press Enter on the computer to start Impedance tracking.Check to see if the VOK and QEN flags turn red under the Operation Status section.'

When I want to enter the value 41 in the Manufacturer Access field I have the following message : 'Automatic Scanning must be stopped before attempting to enter manufacturer access commands that consist of 2 consecutive words'.

I didn't see what I must stop, 'Keep Scanning' check box is not selected and it was marked 'Scan Off' in the bottom of the screen.

Have any idea?

Marc

Hi Marc,

No panic, I think you are still okay,  the message you saw to stop automatic scanning only applies if you want to send a 2 word command but you are not doing this when you send the 41  and/or 21 individually with a return between. These are not 2 word commands. The message is just a warning and appears whenever you type into MAC access window. See section 3 of 5633.slua421a quick start guide for bq20zxx family gas guages.pdf.  2 word commands are like the unseal command shown in fig 26 and permanent fail clear command  shown in fig 21. You should use the 'write 2 word command' button to enter those. You can have 'Continue scanning' selected and the 'write 2 word button'  automatically disables this scanning when it writes the 2 word command.

When you exported you golden file did you first change update status to 02?  After you load the golden files into new battery you can double check update status is 02 and then after you send the 21 command if you read the FLASH again it should show update status  is 06

Mike

Hi Mike,

Yes, I changed the update status to 2 before generating the golden file.

For the warning your right. After I send the 21 command update status changed to 6.

Thanks for your help.

Marc