BQ40Z50-R2: Pulse charging on LifePo battery Packs

Hello Jonathan,

I will need to look into this. We will get back to you next week.

Regards,

Nick Richards

Hi Nick,

Thanks on taking action on this 

will be waiting on your response!

as much details and informations on the pulse charging will be appreciated

Regards

Jonathan Kabangu

Hi Jonathan,

Don't have a further update as of right now. I am waiting to hear back from the battery expert in our team.

Regards,

Nick Richards

Hi Nick,

i'll be patiently waiting for the update!!

Regards

Jonathan Kabangu

Hi Nick,

Is there any update on this item

Regards

Jonathan Kabangu

Hello Jonathan,

The battery expert on our team has been on vacation and is still currently out. I will get back to you when he is back in the office.

Regards,

Nick Richards

Hi Nick,

as we wait for the battery expert to return for the answer

i have also began experimenting on my side

i bought this tool which is capable of doing pulse charging based on it's timing function:

https://www.rigol-uk.co.uk/product/rigol-dp832-linear-dc-power-supply-30v-3a-30v-3a-5v-3a/

Once i get enough data i'll send you the logs 

Regards

Jonathan Kabangu

Hello Jonathan,

That sounds good! I can help debug on the gauging side for certain parameters to make sure that valid charge termination is reached.

Regards,

Nick Richards

Hi Nick,

Last week i left my pack to charge using the pulse charge methods,here's the logs:

009F-01 (1).log

• VCT was not set due to the condition not being seen for 80s
• can't see any other issue ,let me know if you do 

After leaving it to rest during the weekend

Here's the logs 

009F-01.log

• RSOC jumped from 79% to 100% ,is the pulse charging destroying the cells or gauge?

Regards

Jonathan Kabangu

Hello Jonathan,

Can you send the gg file for the gauge?

Regards,

Nick Richards

Hi Nick,

here is the gg file:

009F.gg.csv

Regards

Jonathan Kabangu

Hello Jonathan,

Thank you for sending me the gg file. Please allow me some time to review all the files.

Regards,

Nick Richards

Hi Nick,

Thank you!!

Looking forward to the results/insights from this logs

Regards

Jonathan Kabangu

Hello Jonathan,

Quick update I am still reviewing the files, I should get back to you early next week.

Regards,

Nick

Hi Nick,

Any update on this?

Regards

Jonathan Kabangu

Hello Jonathan,

Sorry for taking a while to get back to you. After looking at the data, the first concern I have in regards to the charging is that the charge does not have a true constant voltage charge. The voltage is not constant when the current starts to taper down.

Regards,

Nick Richards

Hi Nick,

Is this non constant voltage the reason why our RSOC jumped from 79% to 100% ??,

do we know the effect of this non constant voltage on the cells chemistry or the gauge calculation ??

Regards

Jonathan Kabangu

Hello Jonathan, 

I will need to talk to firmware team regarding this, however, my first suspicion is because of the irregular charging behavior.

Regards,

Nick

Hi Nick,

Yes this will be interesting to know how the chemistry is affected by this charging method or if the gauge itself is exhibiting errors due to this charging method!!

Regards

Jonathan Kabangu

Hi Jonathan,

It looks like the one of the cells is out of balanced. Cell-3
Quickest way to balance all cells is to charge each cell individually one by one to full. Then put them together. With the small internal cell balancing current of this device, it might take days to balance. 

Looking at the possible reason of the jump, it looks like the first value of the Ra table updated to a very high value. See below. R_a_0

Is this a new pack? Did you complete a learn cycle and it updated to this? It looks abnormal update. I need more info to determine what could have caused this. 

Hi Jose,

I charged this Pack using a pulsating DC power source,where i charged the pack for 60s(@12V) and a rest of 5s(@0V) every interval,this is contrary to the normal constant current constant voltage method of charging Batteries,is this a possible culprit?

• JK:This is an assembled Pack ,i'm not sure how i can charge each cell individually to achieve the balancing required ,

can you walk me on the steps to charge each cell separately please?

• JK:What does the Ra table mean or show ?,is this the internal resistance of each cell/pack?
• JK:this is a pack manufactured by our supplier!!
• JK: can you guide me on how to perform a learning cycle please?

Regards

Jonathan Kabangu

Hello, 

Please expect a delayed response as Nick is currently traveling for work. 

Regards, 

Robert. 

Hi Jonathan,
Not having a CC,CV mode charger might prevent the gauge from detecting proper valid charger termination. It is possible to make it happen with pulsating DC power mode, but user must follow the VCT section in TRM and ensure VCT is met. 

Jonathan Tshimama-Kabangu said:

can you walk me on the steps to charge each cell separately please?

You might be able to temporary solder jumper wires at each individual terminals. This will give you access to balance them individually. Also, the gauge needs to detect voltage at each VC pin, so somehow you need to have a way to access each individual terminals. The gauge needs to sense VC1,2,3,4. See below

Jonathan Tshimama-Kabangu said:

What does the Ra table mean or show ?,is this the internal resistance of each cell/pack?

Ra is the internal resistance of the cell. Each cell has a unique resistance table. This table updates during discharge. The gauge keeps track of internal impedance to properly track state of health of the battery. Please reference to TRM and also to the Impedance Track algorithm app note. https://www.ti.com/lit/an/slua450a/slua450a.pdf

Jonathan Tshimama-Kabangu said:

this is a pack manufactured by our supplier!!

If you do not have a custom ID, you can send your cells to TI for characterization. This has the benefit of best accuracy and also skips the learning cycle process.

Jonathan Tshimama-Kabangu said:

can you guide me on how to perform a learning cycle please?

Please see the learning cycle app note. https://www.tij.co.jp/jp/lit/an/slua903/slua903.pdf

Video

Hi Jose/Nick,

Sorry for being MIA ,life got in the way

• What are the typical causes for an increase in internal impedance of a cell or pack?,cause in our case the pulsating charge current is what seems to cause it?

• What does the learning cycle tell us about the pack?,just want to know the basics before i perform it

• does the video show A to Z of how to do the whole process of learning cycle?

Regards

Jonathan Kabangu

Hi Jose,

1.What about pulsating method of charging ,can this cause detrimental effect to the chemistry of the cell(impedance) since it's not the conventional CCCV method of charging?

Regards

Jonathan Kabangu

Hi Jose,

interesting!!,one thing i can say is that our charge current is not fixed to a nominal value,our charge IC is random one minute it pulls 850mA the other minute this value may go up to 1A ,is this an issue?

Regards

Jonathan Kabangu