bq20z75 v160 shows improper SOC

Hi Kevin,

Is this the reported SOC at the moment of connecting the device to bqEVSW? After running an additional learning cycle does it still have this kind of discrepancy?

Can you please attach a log of your learning cycle and also a GG file so I can review?

Best,
Justin

Hi Jason,

Yes, 60% is the reported SOC at the moment of connecting the device to bqEVSW.  I have run 2 learning cycles.  No additional learning cycles have been done.

Attached are the learning cycle log and GG files.

Thanks, Kevin

Learning Cycles & GG Files.zip

Hi Jason,

I discovered something peculiar this afternoon. On the battery pack that I cycled twice.....this pack was in a full discharged state showing 0% SOC. I then recharged to 30%SOC as was shown in the bqEVSW. After several hours I disconnected this pack from the bqEVSW for a few minutes. When I reconnected this pack, the SOC was now reading 62% SOC in the bqEVSW and no charge or discharge had taken place. Just wanted to share this with you in case it helps shed some light on this issue.

Thanks,
Kevin

Hi Kevin,

The learning cycle looks like it was completed successfully. One question I do have is how was the ChemID selected? Was a relax-discharge-relax test done in order to determine the ChemID? The reason that I ask is that your resistance tables have updated to a rather odd profile, which may be due to a bad ChemID.

Best,
Justin

Good morning Justin,

I used the TI Chemistry Selection Table from the bqEASY tab within the bqEVSW that showed Molicel ICR18650M is Chem ID 0208.  See attached screenshot.  Is it possible this is incorrect?  I will perform a Chem ID learning cycle and share to log with you to help Identify the proper Chem ID.

Thanks for your help, Kevin

0066.Doc1.docx

Justin,
I just looked through the Chemistry Selection Table again and found a listing for EMoliEnergyCorp ICR18650M (2800mAh) with Chem ID of 2075. Looks like there are 2 listings for the Moli ICR18650M and I managed to pick the wrong one :). I'll try ChemID 2075 and let you know how that work out.
Thanks,
Kevin

Hi Kevin,

It would be best to run a test called a rel-dis-rel (relax-discharge-relax), which is described in this document in section 2.2. (GPCCHEM chem selection tool)

Even if you find an "exact" match in the Chemistry Selection Table, it still may not be the best ChemID. The reason is that even with the same manufacturer and same model number, the batteries will have chemical variances due to the manufacturing process over time, which will lead to them having different resistance profiles. So to make certain, you can run the test as described in the document, and you can use the data to find out which ChemID should provide the most accurate gauging. Also remember that after finding a new ChemID, you will have to rerun your learning cycles for the gauge to update Qmax and its resistance tables. 

Best,

Justin

Hi Justin,

I performed the rel-dis-rel test and the tool gave me a Chem ID of 1278 for the Moli ICR18650M cell. I then ran the learning cycles to obtain the Golden File and programmed 3 prototypes to send to our customer. Our customer has performed some testing…..see attached graph showing SOC values. At approx. 660 minutes the load is removed and no current is flowing…..the SOC is about 5% at this point. From 660 minutes to 960 minutes, the SOC increases from 5% to about 10% with no current flow. Is this something that you would expect to see?.....or should the SOC have remained at around 5%?

 Thanks for your help,

KevinSKMBT_C30016032912540.pdf

Thanks Justin.....appreciate the help.......Kevin