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BQ25820EVM: MPPT Optimization

Christoperson Phodaca
Prodigy 10 points
Part Number: BQ25820EVM
Other Parts Discussed in Thread: BQ25820, BQ25750

Tool/software:

Hi, we are trying to understand the MPPT capability of the BQ25820. Attach is the data we got with a 24V Solar Panel.

The result seems to be having no MPPT. 

What should be done to improve it?

Thanks

MPPT has been Enable with 3mins timer.

  • 0
    TI__Mastermind 31796 points

    Hello Christoper,

    Can you provide a register dump when this is occuring?

    Best Regards,

    Christian

  • 0 in reply to Christian Moyer
    Prodigy 10 points

    Hi Christian,

    Thanks for the response. See register as per attach.

    BRegards,

    Chris

    Fullscreen bq25820-REG-0814.txt Download 
    * Created: Thu Aug 14 15:04:03 CST 2025
*
* Format: Register Name  tab Character,\t  Register Address  tab Character,\t  Hexadecimal register value.
* Device: BQ25820
* BQZ Container: Charger_1_00-bq25820.bqz
*
Charge Voltage Limit	0010
Charge Current Limit	00F0
Input Current DPM Limit	0640
Input Voltage DPM Limit	0348
Reverse Mode Input Current Limit	0640
Reverse Mode System Voltage Limit	03E8
Precharge Current Limit	0140
Termination Current Limit	00A0
Precharge and Termination Control	0F
Timer Control	0D
Charger Control	C9
Pin Control	C0
Power Path and Reverse Mode Control	24
MPPT Control	21
TS Charging Threshold Control	96
TS Charging Region Behavior Control	57
TS Reverse Mode Threshold Control	40
Reverse Undervoltage Control	00
VAC Max Power Point Detected	0348
Charger Status 1	03
Charger Status 2	83
Charger Status 3	02
Fault Status	00
Charger Flag 1	00
Charger Flag 2	00
Fault Flag	00
Charger Mask 1	00
Charger Mask 2	00
Fault Mask	00
ADC Control	A0
ADC Channel Control	02
IAC ADC - Use Field View	0280
IBAT ADC - Use Field View	059A
VAC ADC	2E33
VBAT ADC	14E1
VSYS ADC	2EA6
TS ADC	024F
VFB ADC	0000
Gate Driver Strength Control	00
Gate Driver Dead Time Control	00
Part Information	1A
Reverse Mode Battery Discharge Current	02

  • 0 in reply to Christoperson Phodaca
    TI__Mastermind 31796 points

    Hello Christoperson,

    Your register data indicates the MPPT operation is working. What exactly is happening that makes you think it is not? I'm not really sure what is happening in the graph you provided.

    Best Regards,

    Christian.

  • 0 in reply to Christian Moyer
    Prodigy 10 points

    Hi Christian,

    As per the graph, the solar panel tends to drop (start and end section). Only in the middle section that it is stable.

    The weather becomes cloudy when the solar panel tends to drop.

    Any setting (IC or the components around) we can adjust to prevent this? 

    Thanks,

    Chris

  • 0 in reply to Christoperson Phodaca
    TI__Mastermind 31796 points

    Hello Christoperson,

    What is the time scale?

    Best Regards,

    Christian.

  • 0 in reply to Christian Moyer
    Prodigy 10 points

    Hi Christian,

    Is around 3mins. See attach exported file.

    Thanks

    BQ25820 Result.xlsx

  • 0 in reply to Christoperson Phodaca
    TI__Mastermind 31796 points

    Hello Christoperson,

    Christoperson Phodaca said:
    Is around 3mins. See attach exported file.

    I think this corresponds with your set 3mins timer, after it finds the MPPT voltage it should start looking again after 3mins. Do still see this behavior if MPPT is disable? When this behavior occurs is it activactly looking for MMPT setpoint?

    Best Regards,

    Christian.

  • 0 in reply to Christian Moyer
    Prodigy 10 points

    Hi Christian,

    How to identify that it is actively looking for MPPT setpoint?

    We haven't tested it out yet disabling the MPPT. 

    Do you recommend a longer or shorter timer?

    Thanks

  • 0 in reply to Christoperson Phodaca
    TI__Mastermind 31796 points

    Hello Christoperson,

    Christoperson Phodaca said:
    How to identify that it is actively looking for MPPT setpoint?

    The BQ25820 should have a MPPT_STAT bit REG0x22[1:0]. However, there was a typo in the datasheet, that marked this bit as reserved, which led this to be left out for the BQ25820 GUI. However, it can be accessed using the BQ25750 GUI, or look at bits 1/0 in BQ25820 gui.

    Christoperson Phodaca said:
    Do you recommend a longer or shorter timer?

    If you don't want it seraching as often, I wold recommend a longer time.

    Best Regards,

    Christian.

  • 0 in reply to Christian Moyer
    Prodigy 10 points

    Hi Christian,

    We did some test by changing the search time to 20mins.

    But we do see same waveform the voltage and current are oscillating.

    Is there a way to prevent this or is this normal? What do you think is happening here.

    Thanks

  • 0 in reply to Christoperson Phodaca
    TI__Mastermind 31796 points

    Thanks for posting. It was US holiday on Monday. A team member will look into this and get back to you tomorrow