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BQ24295: Solar Panel input

Julian Chen
Expert 2550 points
Part Number: BQ24295
Other Parts Discussed in Thread: BQ25505, BQ25881, BQ25895

Hi E2E Member,

Our customer use BQ24295 but input source is solar panel (5V), is it OK for this design?

What difference between solar charger and normal charger?

Thanks!

  • 0
    TI__Guru**** 166576 points
    Hi Julian,

    A solar panel has a high output impedance (series resistor at its output), meaning the more current you pull out, the lower its effective voltage drops. There is a maximum power point (output voltage and current) for each panel. For most panels, it is close to 0.8 of the solar panel open circuit voltage. For this panel, that is 0.8 *5V = 4.0V. You can use the charger's VINDPM feature to regulate its input at the MPP point and get maximum panel current. But, that means that with this panel running at its MPP = 4.0V, the buck based charger will never fully charge the 4.2V battery. You could then increase the VINDPM setting and get lower current but that means longer charge time. What is the panel's maximum power point current? A boost based charger like bq25505/70 if low current or bq25881 if high current might be a better choice.
  • 0
    TI__Expert 8230 points

    Hello Julian,

    A 5V solar panel would work as an input for the bq24295. If using a solar panel, you would need some sort of MPPT algorithm to extract the most out the panel for it to be able to charge the battery. A regular DC input would just be limited by the rated power it can provide.

    I recommend reviewing the following reference design that discusses an implementation of a MPPT algorithm using a similar device, bq25895.