• State TI Thinks Resolved
  • Locked Locked
  • Replies 13 replies
  • Answers 5 answers
  • Subscribers 63 subscribers
  • Views 154 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ25820EVM: How use this board as a discharger?

Gamini Dharmasena
Prodigy 50 points
Part Number: BQ25820EVM
Other Parts Discussed in Thread: BQSTUDIO, BQ25820

Tool/software:

Hello,

We are trying to use BQ25820EVM as a Charger & a Discharger.   I figured out how to use the eval board as a charger, but I couldn't get it to work as a discharger to discharge the battery stack. We are using a 13S Li-ion battery pack which is connected to J3. on the board. The load is connected to  J1. I thought the Reverse Mode should come up automatically, but it didn't. Are there any bits that I need to set up in the BQStudio interface or any jumper settings? Any help is greatly appreciated.

Thanks

Gamini

  • 0
    TI__Mastermind 31816 points

    Hello Gamini,

    Gamini Dharmasena said:
    We are trying to use BQ25820EVM as a Charger & a Discharger.   I figured out how to use the eval board as a charger, but I couldn't get it to work as a discharger to discharge the battery stack. We are using a 13S Li-ion battery pack which is connected to J3. on the board. The load is connected to  J1. I thought the Reverse Mode should come up automatically, but it didn't. Are there any bits that I need to set up in the BQStudio interface or any jumper settings? Any help is greatly appreciated.

    Reverse mode is not enable automatically. You will need to enable reverse mode and/or auto reverse mode. You can also apply load to J2 instead, if you do not have a host device

    Best Regards,

    Christian.

    Best Regards,

    Christian.

  • 0 in reply to Christian Moyer
    Prodigy 50 points

    Hi Christian,

    Many thanks for the prompt response. I did enable the reserve mode, but nothing is happening. The following is the screenshot of the bit settings.

  • 0 in reply to Gamini Dharmasena
    TI__Mastermind 31816 points

    Hello Gamini,

    Why are the status registers blank?

    Best Regards,

    Christian

  • 0 in reply to Christian Moyer
    Prodigy 50 points

    Hi Christian,

    Stil no luck with discharging. Here is the info on the Status registers.Your help is greatly appreciated. Thanks, Gamini

     

  • 0 in reply to Gamini Dharmasena
    TI__Mastermind 31816 points

    Hello Gamini,

    Your VSYS_REV is too low, the voltage needs to be higher than battery voltage.

    The BQ25820 is a buck charger in forward mode and a boost charger in reverse mode.

    Best Regards,

    Christian.

  • 0 in reply to Christian Moyer
    Prodigy 50 points

    Hi Christian,

    I set that value to 54600mV and still not discharging.... Are there any jumpers on the eval board that has to be changed? Thx. Gamini

  • 0 in reply to Gamini Dharmasena
    TI__Mastermind 31816 points

    Hello Gamini,

    Did you apply load to J2? The ACFETS block the flow of current to J1 during reverse mode. Load should be applied to J2.

    Best Regards,

    Christian.

  • 0 in reply to Christian Moyer
    Prodigy 50 points

    Hi Christian,

    J2 is always hot regardless of whether reverse is enabled or disabled. As long as the battery is connected, J2 is always showing the Batt V and starts discharging. Hoiw do I control J2?

  • 0 in reply to Gamini Dharmasena
    TI__Mastermind 31816 points

    Hello Gamini,

    • When the device is in battery only mode, the BATFET will be open and the battery will directly supply power to J2, but the the J2 voltage will be around the same voltage as VBAT.
    • If you want to control this voltage, you will need to set VSYS_REV to whatever value you want(has to be above VBATT). Then you will enable reverse mode. The J2Voltage should be the same as VSYS_REV.

    battery-only mode: VSYS=VBAT..

    reverse mode- VSYS=VSYS_REV

    Best Regards,

    Christian

  • 0 in reply to Christian Moyer
    Prodigy 50 points

    Hi Christian,

    How do you put the device in battery-only mode?

    What I meant was J2 cannot be switched ON/OFF as it is always hot whenever the battery is connected to J3. We don't want that as we don't want to hot plug either the load or the battery. We should be able to switch OFF the BAT voltage showing up on J2.

    The status says the BATFET is off...

    How do we switch off and on power on J2?

    Many thanks Gamini

  • 0 in reply to Gamini Dharmasena
    TI__Mastermind 31816 points

    Hello Gamini,

    Gamini Dharmasena said:
    How do you put the device in battery-only mode?

    Battery only mode just refers to the battery being the only power source. There is no entering battery only mode. it's just the condition of battery being the only power source.

    Gamini Dharmasena said:

    We don't want that as we don't want to hot plug either the load or the battery. We should be able to switch OFF the BAT voltage showing up on J2.

    The BATFET is shutting off, but the power is still flowing through the diode of the Fet. If you want to completely disconnect this path, you will need two MOSFETS.

    You will need to populate Q8 and C36, and remove R1005/R1004

    Best Regards,

    Christian.

  • 0 in reply to Christian Moyer
    Prodigy 50 points

    Many thanks. Christian. What is the purpose of J2? Is there a way to charge and discharge only using J1 & J3? In our case, we may not be able to have 3 connectors. I can charge the battery without J2 but cannot discharge.

    Thanks

    Gamini

  • 0 in reply to Gamini Dharmasena
    TI__Mastermind 31816 points

    Hello Gamini,

    J2 is the system load

    When the adapter is outside of the ACUV/ACOV range( adapter is removed) the ACFETS will be latched off and power is not able to flow to J1. We do not have a safe way for Battery to flow from J3 to J1.

    If you remove the ACFETS, the battery will be able to flow from J3 to J1, but when you plug the adapter in. The adapter will be shorted to battery. This could damaged the adapter or battery.

    Best Regards,

    Christian.