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Solar panel for my BQ25504

Harry
Expert 2920 points
Other Parts Discussed in Thread: BQ25504

Im searching for a proper  solar panel for my harvesting chip BQ25504.

Can anyone suggest me proper open circuit voltages that I should get to fix as a power source?  the datasheet suggests that 3v, 400mW is max. So are these conditions to be met by the open circuit Voltage and current or am I allowed to buy a solar panel a little higher than these voltages such as 5V ? 

it is my intention to use these chips in parellel so that inuput power to the system is more than 400mW so I hope I dont need to worry much about the o/p current of the solar penel since I can devide in among the parrel BQ25504 chips.

Could anyone please advice me as to how I could chose the best max voltage of my Solar panel for this specific IC?

  • 0
    TI__Guru**** 167146 points

    The bq25504 is only a boost converter.  It cannot step down an input voltage.  So, using a solar panel that could provide a voltage that is higher than VSTOR is generally not recommended.  You will be setting the input regulation (via the MPPT resistors) to approximately 80% of the solar panel's VOC in order to reach the maximum power point.  So, I recommend getting a panel with VOC*80% <=  VSTOR for your maximum lighting level in order to get best efficiency.

     

     

  • 0 in reply to Jeff F
    TI__Guru**** 167146 points

    After discussing with the designer, we have concluded that you cannot easily drive several bq25504 from 1 solar panel.  The problem is the MPPT sample and hold feature.  There is no easy way to synch the multiple bq25504 ICs so that they all stop boosting and sample the true VOC of the panel at the same time.  The best solution is a separate panel for each converter, which is actually easy to implement because a high voltage panel is comprised of several 0.7V panels in series.  You would simply need to break the connections.