BQ34Z100-G1: No Qmax update after full charge though FC set and OCVTAKEN set

user5014632

Part Number: BQ34Z100-G1
Other Parts Discussed in Thread: EV2400, BQSTUDIO

Hi,

I have run up to ten learning cycles without issues on LFP batteries with an EV2300 and Bqstudio V1.3.54, today I switched to an EV2400 with BQstudio V1.3.86 and a new chemID (still LFP).

I followed the same procedure and the charge and discharge phases went smootlhy, however at the end of the learning cycle the learned status remained 0x04.

Deeper analysis of bqstudio logs shows that FC, OCVTAKEN and VOK bits behaved correctly during the learning, i.e. full charge was correctly detected and OCVs were correclty taken during rest periods.

I have endured many failed learning in the passed and I understood through the forum the importance of these indicators. However this behavior is new to me and I can't find similar cases on the forum. Could you please have a look in the log and gg.csv files enclosed and share your insights? (The gg.csv file shows only the modified values at the beginning of the learning cycle before calibration, all other values are firmware default, I do not have the gg.csv file after failure)

12.8V_33.5Ah_LiFe_setup_failed_learning.gg.csv

12.8V_33.5Ah_LiFe_failed_learning.log

Here are the peculiar differences I found by comparing the log to a previous successful learning:

DoDatEOC took a positive value (412) when FC was set (while it stayed 0 on a successful learning);
Qstart took a negative value (-211) when FC was set (while it was set to 0 on a successful learning);
RemCap, FullChgCap, TrueRC and TrueFCC decreased slightly when FC was set (while they use to slightly increase during previous successful learnings);
StateTime was reset a few seconds after FC was set (while it continued to increase on a successful learning);
DOD0PassedQ, DOD0Time and DOD0 were set to 0 when FC was set (as in a successful learning), however QmaxDOD0 and QmaxPassedQ continued to increase (while they seem to be set to 0 when the learning is successful).

Another funny I had is the following information message when programming the chemID:

However a quick search on the forum reported that it would not jeopardize the learning procedure.

Hope you will be able to make sense of all these clues.

Best regards,

Jérémie

over 5 years ago

0 Wyatt Keller over 5 years ago

TI__Guru** 106170 points

Hello Jérémie,

We will look into this more and get back to you soon.

Sincerely,

Wyatt Keller

0 Andy Liu (BMS) over 5 years ago in reply to Wyatt Keller

TI__Guru 52115 points

You can ignore that warning. I can see the same warning. It should not the cause of your failure.

I see you have provided your log and gg files, which are very helpful. Let me take a look at them and I will provide my feedback tomorrow.

Andy

0 Andy Liu (BMS) over 5 years ago in reply to Andy Liu (BMS)

TI__Guru 52115 points

I took a quick look. The root cause is that the DOD0 captured by the gauge was not low enough when the batteries were charged to full. Which chemistry id do you use? Can you share your GPC report if you have it? Thanks.

Andy

0 user5014632 over 5 years ago in reply to Andy Liu (BMS)

Intellectual 515 points

Hi all,

Thank you for your quick answer and interest in this issue. I prefer sending our chemID privately since it can disclose the manufacturer of our cells, same thing for the GPC report. I'll be glad to send it as soon as possible so we can tackle this issue and move forward.

Can you elaborate a bit more about DOD0, I made a lot of golden images for several batteries and I have trouble making sense of this piece of data. For example, DOD0PassedQ and QmaxPassedQ are quite close to the design capacity and Qmax0 of the battery. If I test another battery with twice the capacity, those value are roughly twice also. However DOD0 and QmaxDOD0 are the same order of magnitude no matter the capacity of the battery. Can you explain how they are calculated and how they should behave in relation to the battery parameters in order to achieve a successful learning?

Hope you'll be able to explain the root cause of this issue.

One thing that could save time in the meantime: If I manage to have a successful learning with another chemID (LiFePO4 as well), does that mean that this other chemID is legit and can be used for this battery?

Best regards,

Jérémie

0 Andy Liu (BMS) over 5 years ago in reply to user5014632

TI__Guru 52115 points

You can add me as a friend and send the GPC report to me in a private message?

Andy

0 user5014632 over 5 years ago in reply to Andy Liu (BMS)

Intellectual 515 points

Hi Andy,

You do not appear in my friend list yet. Have you validated my request?

In the meantime, could you tell me more about DOD0 and if another chemID can be used if the learning is successful?

Best regards,

Jérémie

0 user5014632 over 5 years ago in reply to user5014632

Intellectual 515 points

Hi Andy,

If the friend request does not work, can you reach me on my e-mail address?

Could you please also confirm whether another chemID can be used if the learning is successful, so I can continue testing in the meantime?

To go further on this issue, you will find below two sets of data (gg.csv and log):

the 1st one is a successful learning done with an EV2300 and a chemID I have used successfully for two years;
the 2nd one is a failed learning with an EV2400 and only the chemID modified to match a new cell model.

Both were performed with the same battery with this new cell model. Which would mean that either the EV2400 or the new chemID are responsible for the failure.

EV2300 successful learning:

OLD_chemID_12.8V_16.75Ah_GI_learned.gg.csv

OLD_chemID_12.8V_16.75Ah_GI_learning.log

EV2400, new chemID failed learning:

5367.NEW_chemID_12.8V_16.75Ah_GI_FAILED.gg.csv

NEW_chemID_12.8V_16.75Ah_GI_FAILED_learning.log

Thank you for your help.

Best regards,

Jérémie

0 Andy Liu (BMS) over 5 years ago in reply to user5014632

TI__Guru 52115 points

A DOD0 is captured when the battery pack is discharged to empty and relaxed. Also, another DOD0 is measured when the battery pack is charged to full and relaxed. The difference between these two DOD0s must be bigger than 14746. However, I can see in your log file, the difference cannot meet that requirement. See the plot below.

Try to charge the battery pack until a lower tapper current is achieved. When I do a learning cycle, I usually wait until the tapper current is C/50 or even C/100.

0 user5014632 over 5 years ago in reply to Andy Liu (BMS)

Intellectual 515 points

Hi Andy,

Thank you for your answer. I managed to have a successful learning with my old chemID and I noticed that on successful learnings the QmaxDOD0 is set to 0 as soon as FC is set. You will find the log and gg.csv files of this successful learning below:

LiFe_12.8V_33.5Ah_GI_SUCCESS.gg.csv

LiFe_12.8V_33.5Ah_GI_SUCCESS.log

For reference here is again the log of the failed learning with the new chemID:

LiFe_12.8V_33.5Ah_GI_FAILED.log

However I cannot explain why with the new chemID QmaxDOD0 is set to a higher value and only after resting. Could you compare the two logs and tell if the problem comes from my learning process or from you chemID?

Could you also indicate how QmaxDOD0 is calculated? A high Depth of Discharge value when the battery is fully charged is quite counter intuitive to me.

And once again, is this successful learning usable even if the chemID is not exactly the one given by manufacturer?

Best regards,

Jérémie

0 Andy Liu (BMS) over 5 years ago in reply to user5014632

TI__Guru 52115 points

What are the old and new chem id? I would need to check their OCV tables.

Andy

0 user5014632 over 5 years ago in reply to Andy Liu (BMS)

Intellectual 515 points

Hi Andy,

Please see my pending friend request, I wrote the chemID in the message. I prefer not to disclose them publicly.

Best regards,

Jérémie

0 Andy Liu (BMS) over 5 years ago in reply to user5014632

TI__Guru 52115 points

I have just accepted your friend request. However, I didn't get any message. Coul you send your message to me again.

Andy

0 user5014632 over 5 years ago in reply to Andy Liu (BMS)

Intellectual 515 points

Hi Andy,

Did you receive my last message with the chemIDs? Did you had time to look at the OCV tables?

Best regards

0 Andy Liu (BMS) over 5 years ago in reply to user5014632

TI__Guru 52115 points

Yes. I have got your message. I will take a look and get back to you tomorrow.

Andy

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BQ34Z100-G1: No Qmax update after full charge though FC set and OCVTAKEN set