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BQ24780SEVM-583: Configuration for NiMH battery

Rajesh Kaliyaperumal
Intellectual 930 points
Part Number: BQ24780SEVM-583

Hi ,

I am having BQ24780SEVM-583. I want to charge and discharge NiMH battery with this EVM.

I am using 6 series cells of NiMH battery each cell having a voltage of 1.2 volts & 2500mAH. So total Pack voltage is 7.2 Volts .

I have discharged battery with the resistive load upto 5.6 Volts and tried to charge the battery with the charge current of 0.5 A using the EVM.

Input voltage to the EVM is 19 Volts.

Whenever I am trying to charge the battery, it is always charging in Constant voltage mode charging not in constant current charging mode.

I have tried to charge the battery with increased battery regulation voltage of 9 Volts as well to check if the charging is happening in constant current mode. But it is not happening.

The reason why we need to charge the battery in constant current mode is to see the  " delta V " trend in NiMH battery charging as shown below.

Could you suggest us a way to charge NiMH battery using this EVM and how to configure it for the same ?

Appreciate your help at the earliest.

Reagrds,

Rajesh K

  • 0
    TI__Genius 13605 points

    Rajesh,

    Good day. I may know what's is your system set up? Below photo is our suggested test Setup diagram. You should need 2 power supply, one is 19V, the other is 3.3V. And did you install TI GUI tool to link with EVM board?

    Thank you and Regards

  • 0 in reply to Paul Yeh
    Intellectual 930 points
    Hi Paul,

    I have connected 2 power supply as suggested in the user guide i,e one is 19 Volts & other one is 3.3 Volts.
    I have also installed Battery Management Studio for configuring the charger IC using SMBus. I have used eval board EV2300 to communicate with charger IC.

    Regards,
    Rajesh
  • 0 in reply to Rajesh Kaliyaperumal
    TI__Genius 13605 points

    Rajesh,

    Did you have battery simulator on hand? if yes, could you due this equipment to test again?

    And from your spec. it seems your charge current is small, around 0.5A. Have you tried program higher, maybe 1A or higher?

    Another possible is charger enter IINDPM condition, can you also double check input current limit setting?

    Thanks

  • 0 in reply to Paul Yeh
    Intellectual 930 points

    Hi Paul,

    I have set the input current limit as 4096 mA and Discharge current limit as 1024 mA whereas the actual discharge current is about 150mA. I think the charge current is not reduced gradually due to DPM of charger IC.

    I have also tried to charge the battery with the higher charge current of 1A instead of 0.5 A, Still I am not able to charge the battery in constant current mode.

    I have also noticed that there is a difference in the set charge current and actual charge current at which the battery is charging. For example if we set the charge current as 512 mA using the Battery Management studio , the actual charge current read in Ammeter is only 400mA. What is the reason for the difference in the set charge current and actual 

    What is the reason the mismatch in the charge current ??

    Why am I not able to charge the NiMH battery in constant current mode ?

    Regards,

    Rajesh K

  • 0 in reply to Rajesh Kaliyaperumal
    TI__Genius 13605 points

    Rajesh,

    What is the reason the mismatch in the charge current ?? 

    [PY] In general, maybe charger is in CV mode, so the charging current will reduce. Did you use battery simulator to evaluate already?

    Why am I not able to charge the NiMH battery in constant current mode ?

    [PY] Not sure why, but could you try Li-Ion battery to double check is your symptom the same or not. And could you advise what is your NiMH battery model and I can try to evaluate in my lab as well?

    Thank you and Regards

  • 0 in reply to Paul Yeh
    Intellectual 930 points
    Hi Paul,

    We have not used Battery simulator yet . We will try to get one.

    Also will checked with Li-Ion battery 4S1P configuration and I can see the Constant current mode charging till it reaches 16.5 Volts (which the voltage set using Battery management studio) and Constant voltage mode as well.

    We have used Camelion AA NiMH cell 1.2 Volts & 2500mAh (NH-AA2500ARBP2) in 6 series cell configuration.

    Regards,

    Rajesh
  • 0 in reply to Rajesh Kaliyaperumal
    TI__Genius 10240 points
    Rajesh,

    We haven’t heard back from you, I’m assuming you were able to resolve your issue. If not, just post a reply below or create a new thread if the thread has locked due to time-out.