• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 907 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.

BQ24210: Setup for solar panel as power supply: DPM and LPCM feature

FranMartin
Intellectual 600 points
Part Number: BQ24210

Hello!
I am planning to use the IC BQ24210 to charge the battery of a small IoT system. These are the general system characteristics:

SOLAR PANEL

  • Voc = 5,8 V
  • Vmp = 4,35 V (Voc -25% approx.)
  • Isc = 225 mA

BATTERY

  • Type Li-Po 1 cell
  • Nominal Voltage 3.7 V
  • Nominal Capacity 2400 mAh
  • Standard Charge Current 480 mA
  • Max Charge Current 4800 mA
  • Charge cut-off Voltage 4.20+/-0.05 V
  • Discharge cut-off Voltage 2.75 V

LOAD CONSUMPTION

  • Constan consumption average current < 25 mA

QUESTIONS

  1. To try to extract the maximum energy from the solar panel, what is better? set the DPM feature for battery tracking or set the VBUS-DPM threshold to the maximum power output voltage of the solar panel (Vmp=4.35V for my solar panel)?

  2. To ensure that the solar panel is not required more current than it can supply, and therefore prevent it from collapsing. Would it be convenient to limit the constant fast charge current to a lower value short-circuit current of the solar panel? Or, however, can it be set to a higher current because the DPM feature prevents the solar panel from collapsing?For solar panel, LPCM feature is desirable, right? So, the TS pin should be at high. What to do with the VTSB pin? Let it floatting or not use a pull-up for TS pin and connect TS pin and VTSB pin?

  3. In 4.3 (Figure 5). Why are capacitors C2 and C4 assembled and not only C1 and C3? In the data sheet I can not find this information.

Best regards and thanks.

Fran Martin.

 

 

  • 0
    TI__Guru**** 165786 points
    Fran,

    Regarding 1, if you are confident that your light source will be able to consistently power the panel and the panel temperature will not fluctuate thereby changing the VOC and MPP points, I suggest setting the VBUS_DPM threshold. If not and the MPP point will fall below the battery voltage, then I suggest battery tracking.

    Regarding 2, the DPM feature will limit the charge current but as a redundancy, I suggest not setting the charge current higher than the ISC. LPCM is not required for a solar panel but in case, becasue the battery capacity is so large and your panel can only provide 225mA max, I recommend LPCM with safety timers held in reset. Otherwise, the safety timer will likely time out before your battery fully charges.

    Regarding 3, the EVM was a bit overdesigned. The recommended minimum capacitances of 1uF per the datasheet on VIN and OUT are all that is required. More capacitance is acceptable at each pin.
  • 0 in reply to Jeff F
    Intellectual 600 points

    Hi Jeff and thanks.

    Jeff F said:


    Regarding 1, if you are confident that your light source will be able to consistently power the panel and the panel temperature will not fluctuate thereby changing the VOC and MPP points, I suggest setting the VBUS_DPM threshold. If not and the MPP point will fall below the battery voltage, then I suggest battery tracking.

    Because I can not know if the light source is going to provide a consistent source, I think it's better to choose a conservative solution and use the battery tracking feature. In this case I understand that the only configuration required is to leave the VDPM pin floating, it is right?

    Jeff F said:


    Regarding 2, the DPM feature will limit the charge current but as a redundancy, I suggest not setting the charge current higher than the ISC. LPCM is not required for a solar panel but in case, becasue the battery capacity is so large and your panel can only provide 225mA max, I recommend LPCM with safety timers held in reset. Otherwise, the safety timer will likely time out before your battery fully charges.

    In point 8.4.5.10, page 19 of the datasheet, it is said that the LPCM feature is normally used for solar charging applications and also the timers is held in reset (the pre-charge timer and 10 hour safety timer). To implement this feature,is it enough to connect the VTSB and TS pins? Or is it better to connect a pull-up resistor on the TV pin and keep the VTSB pin floating?

    Jeff F said:


    Regarding 3, the EVM was a bit overdesigned. The recommended minimum capacitances of 1uF per the datasheet on VIN and OUT are all that is required. More capacitance is acceptable at each pin.

    Resolved the question 3

    Thanks.

    Fran Martin.

  • 0 in reply to FranMartin
    TI__Guru**** 165786 points
    VDPM floating is battery tracking.

    TS pin must be pulled high relative to the VTSB pin to enter LPCM. So you either short them directly or use a resistor divider to set V(TS) at least 85% of VTSB voltage. The resistor divider allows more flexibility in case you change your mind later.