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BQ25792: Solar lithium 3S battery charger (software problem solved?)

Javier Herrero de la Cal
Intellectual 370 points
Part Number: BQ25792
Other Parts Discussed in Thread: BQ25798, BQ25798BKUPEVM, BQ25798EVM

Hello, 

In the past I made the following question and thread for the problem we had with the BQ25792.

https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/987798/bq25792evm-charging-problems-with-solar-panel-load-and-battery 

As you can see, Jeff told me that there was a software problem in the BQ25792 that did not let it work with solar panels.

We have now a new project where we need to make a device with solar panel, 3s lithium battery. I mean, it is not to only charge the battery but also to power the device that work 24/7.

Please, let me know if we can use the new BQ25792 since we have the PCB designed with this chip and we could just solder the chip with the new software if it is prepared.

Thanks and best regards

  • 0
    TI__Guru**** 165766 points

    Hi Javier,

    The BQ25798 is the spin that is recommended for solar panels.  Unlike the 792, it will not put the charger in HiZ after repeated poor source detections.  It has an auto MPP setting that can be enabled after power up.  It is not enabled by default.  Also, the MPP feature auto disables once the battery voltage drops below the MINSYS setting so I recommend setting MINSYS to the lowest value that the system can accept.

    Regards,

    Jeff 

  • 0 in reply to Jeff F
    Intellectual 370 points

    Hello Jeff, This is what you told me. The BQ25792 do not pult the charger in HiZ when after 14 times when the voltage is below some level, it will not charge the battery. But you told me that it was becase the software and you would solve this in some months (some months ago). So, BQ25798 is pin to pin as the BQ25792? I mean, can we just solder the BQ25798 in the PCB we made for the BQ25792? To be sure it works ok, is any firmware version that we have to buy it for make it work? Or if the chip is old, maybe it does not work ok?

    Thanks for your help and best regards

    Javier

  • 0 in reply to Javier Herrero de la Cal
    TI__Guru**** 165766 points

    Hi Javier,

    Yes, its pin to pin.  Technically not a software change but a change to the async state machine inside the chip.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Intellectual 370 points

    Ok, but I have seen now that there will not be stock till the end of this year. I think that what we will make is order  the EVK of the BQ25798 and unsolder the chip and solder it in our PCB for start again to make the tests. Would be possible to get any sample of the chip? In the past we had a big problem with our customer with the BQ25792 as you know and now we would like to tell them that we have found a solution and show it him. Thanks

  • 0 in reply to Javier Herrero de la Cal
    TI__Guru**** 165766 points

    Hi Javier,

    Unfortunately, due to supply chain issues, we are having to ration ICs based on opportunity.  Can you provide your customer's mass production date and expected quantity and end application?  Also can you provide number of samples you need?  I will put in the request to my management and let you know if/when approved.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Intellectual 370 points

    Hello Jeff. Our customer will need about 500 units in this project. About the samples with 5 units I think it would be ok, since I think that the 500 units will be need in 2022. I have to travel to Ecuador at the end of November and I have to go there with a sample (sample of the device, including the charger). So if samples cannot be arrive here in the next 3 weeks I think that what we will do is buying the EVM and unsolder the chip and solder the chip in our PCB.

    Javier

  • 0 in reply to Javier Herrero de la Cal
    TI__Guru**** 165766 points

    Hi Javier,

    We will not be able to meet your November deadline.  Your idea about removing ICs from the EVM is a good one.  There are 2 EVMs for 798, BQ25798EVM and BQ25798BKUPEVM.  If you haven't signed up for notifications on the samples.ti.com website, keep checking the sample website at least twice a week as inventory levels change weekly.

    Regards,

    Jeff 

  • 0 in reply to Jeff F
    Intellectual 370 points

    Thanks. Yes, I can enter in samples.ti.com but the SEND button does not work when I enter in Notificate me when the samples with be available. I write the quantities (5) and my email and SEND.... does not work, only CANCEL.

  • 0 in reply to Javier Herrero de la Cal
    TI__Guru**** 165766 points

    Hi Javier,

    That's odd.  It worked for me. To confirm, you logged into your ti.com account first and then your email address showed up in the box above SEND and CANCEL box? 

    I will submit a ticket for the www.ti.com people to investigate.  If I get notified, I will contact you.

    Regards,

    Jeff 

  • 0 in reply to Jeff F
    Intellectual 370 points

    Hello Jeff. I enter in samples.ti.com. Then I place my email and passport and it shows that I have entered ok since I can see my name in the website. Then, I search the BQ25798, the websiste show it and there is a link to Notify me when available. I press that link and then it open an screen to select how many samples i want and have my email already written. Then if I press SEND, anything happend. I have checked it with Chrome and Microsoftt Edge and it does not work in any of them. But If I press CANCEL... then it works.  I have checked some things but I seems that everything in my PC is ok. So, I think it is an error in the website or something related with the security. Let me know if TI has solve it or how can I do that. I already ordered the EVK and I will tell you something if it works ok once we will unsolder the chip and solde it in our PCB. Best regards

    Javier