BQ40Z60: Qmax not updated on Fast Qmax update procedure

Hello Widji,

Can you also share your .gg file? The Update Status must also be 0x0E in order for fast Qmax updates to work, have you completed the learning cycle for the battery and programmed the correct chem ID?

Sincerely,

Wyatt Keller

Hi Wyatt,

Attached the gg file. As far as we know, we already finished the learning cycle using Sony VTC6 cell 214148a-092421.gg.csv

Hi Wyatt,

Do you have any other clue I have to consider regarding this issue? is there any fault in our procedures or BMS configurations?

Thanks,

Widji

Hello Widji,

During your test did you get at least a 85% DOD change? The Qmax may not complete if you don't cycle by atleast 85% DOD.

Sincerely,

Wyatt Keller

Hi Wyatt,

If we talk about Delta SOC, I could say it's more than 90% because I charged to VCT (100% RSOC), and discharge to almost 5%.

Do you have idea where I can find the DOD change percentage?

Hello Widji,

That should be enough change in DOD, I will need to take a closer look at the data tomorrow.

You were able to get Qmax updates during the learning cycle, it's just the fast Qmax updates that are not being completed?

Sincerely,

Wyatt Keller

Hi Wyatt,

I already do Fast QMax update procedure for several cycle and seems like the update isn't always occurred every cycle I did.

Just for your reference, I attached cycle by cycle Qmax value in the chart below

Hello Widji,

The Qmax does not need to update every cycle, that is normal. As long is it updates regularly gauging should not be affected. If you were not able to get any fast Qmax updates at all, this would be an issue for gauging accuracy over the lifetime of the pack.

Sincerely,

Wyatt Keller

Hi Wyatt,

Sure. I can understand if fast QMAX isn't update in every cycle. But what I don't understand is how often should QMAX update is needed, because this is related with my previous question about how often QMAX should be updated and He said QMAX need to be updated in every cycle.

Besides, did you find what is causing the QMAX isn't updated from the log, so maybe in the future I can predict how and when to update the QMAX on demand and make sure the update is successfully occurred?

Very appreciate for your help.

Hello Widji,

Ideally we would like to see a Qmax update every cycle, but it's okay if you have multiple cycles without one. You can see in the TRM that MaxError will increment by 0.05% per cycle. So you can cycle 10 times without an update and still only have 0.5% max error.

I'm not able to see which condition exactly is preventing a Qmax update, but one of the conditions is not being met. I think it is strange that your design capacity is set to 3000mAh but the Qmax is updating to over 3500mAh, the design capacity is used in limiting some factors for Qmax so it may be part of the issue.

Sincerely,

Wyatt Keller

Hi Wyatt,

I think so. If I read SLUA997, Fast QMax update occurred in every cycle and it tend to decrease cycle by cycle until it close to initial QMax from the optimized cycle. But, in our experiment environment, the QMax update tend to increase cycle by cycle and it's going farther from our initial QMax. 

In your experience, what do you think caused the QMax calculation error?

Hi Wyatt,

Thanks for the enlightenment, let me take a look closer to design capacity.

Hello Widji,

Let me know if you have more questions.

Sincerely,

Wyatt Keller