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BQ25505: Is it compatible with Voc = 5.65V and Isc = 200 mA solar panel?

Part Number: BQ25505

Hello,

I'm thinking of using your IC to control the charge of a 3.7V and 2500 mAh lithium polymer battery. As for the solar panel, for now the manufacturer has only given me Voc = 5.65V and Isc = 200 mA. My question is whether the BQ25505 could support this solar panel since its maximum input voltage is 5.1V but the MPPT of the solar panel would be around 4.5V. As for the maximum input current I do not know if it could support up to these 200 mA. Thanks and best regards.

  • Fran,

    Two things, You might need a clamp to prevent the voltage from going beyond the abs. max voltage. Also there is a chance that the MPPT algorithm might take a set point to the max of the clamp voltage and not necessarily the true OC voltage under max. light condition.

    Regards,
    Gautham
  • Hi Gautham!
    Thank you but regarding the second question I asked (maximum input current). I think the circuit would not work by power terms, right? Suppose I use a zener diode to calmp with Vz = 5.1 V and I program an MPPT voltage of 4.25 V (approx 5.65V * 0.75). In this case, if we approximate the current in MPPT as Isc * 0.85 we have Imppt = 0.85 * 200 = 170 mA. Therefore, the power in the MPPT is 4.25 * 170 = 725 mW which is higher than 510 mW. Is the reasoning correct?
    Thanks for your help.
  • Fran,

    Please refer to the harvesting element's datasheet to determine effective I you can get at a particular V. 

    MPPT calculations use voltage. If the voltage of the clamp prevents the charger from seeing the actual OC voltage, then the power extracted could be lower. 

    regards,

    Gautham