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BQ25071: Replacing battery with a supercap

ELSA JOHN
Prodigy 100 points
Part Number: BQ25071
Other Parts Discussed in Thread: BQ25173, BQ25173-Q1

Tool/software:

Hi TI Team,

We are designing a system which can provide backup through both a Supercap as well as a battery. What will happen if I use BQ25071 to charge supercap instead of battery? Will any protection feature prevent the supercap from functioning properly? The super cap can be rated to 4V and capacitance of 1F. 

  • 0
    TI__Mastermind 40325 points

    Hello,

    Precharge will limit the lower voltage charging. It really depends on the specifications of the battery, including charge current rating, charge voltage rating, etc. Just at first glance, the charge voltage regulation for this part is 3.5V, so getting to the full 4V supercap would be a challenge. Also, this part will charge to the overcharge voltage and then lessen with lower current to a float voltage.

    Take a look at the BQ25173 or BQ25173-Q1 (better thermals than BQ25173).

    Regards,

    Mike Emanuel

  • 0 in reply to Michael Emanuel35
    Prodigy 100 points

    Hi Mike,

    Super cap charging of 3.5V max will be ok. It is not necessary to charge the supercap until the rated voltgae. Otherthan precharge will there be any expected faulty conditions?

  • 0 in reply to ELSA JOHN
    TI__Mastermind 40325 points

    The device will struggle to charge at full current when in low battery because this is a LDO charger. It has to dissipate all the power not used.