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BQ25176M: to charge a super capacitor?

gustavo zarba
Expert 1110 points
Part Number: BQ25176M
Other Parts Discussed in Thread: BQ25570, BQ25176, BQ25173, TIDA-00588

Hi dear people,

I am considering the BQ25570 for an Energy Harvesting Design getting the energy from a piezo element and charging a super capacitor.

However, the BQ25176 looks very interesting, because it is linear (less noisy?) and the circuit looks much simpler than by the BQ25570.

The question is: would I be able to charge a super capacitor, instead of a battery?

The reason for using a super cap instead of a battery is because I need a quick start of my system with a depleated power element.

By a Battery this would take time and my hope is this could be quicker with a capacitor.

Thanks for the help and

kind regards,

Gustavo

  • 0
    Expert 1110 points

    Hi,

    I just discovered the BQ25173, which is targeted to charge super capacitors. With this, I have the answer, but maybe I can add a second question:

    On TIDA-00588, Enery Harvester Boooster Pack, a BQ25570 is used to charge a super cap or alternatively a battery. (As I understand, this could happen simultaneously?)
    Would then the BQ25176 be able to do this? Having a supercap and a LiFePO4 cell would be convinient.

    Sorry for the confusion,

    best regards,

    Gustavo

  • +1 in reply to gustavo zarba
    TI__Guru 68906 points

    Hello Gustavo

    The LiFePO4 or Li-Ion battery would need to be paired with correct charger type.

    BQ25173 will only charge a supercapacitor.

    BQ25176 could charge both Li-Ion or LiFePO4, needs the right setting.

    Could a super cap be placed in parallel with the above battery -- should check with battery manufacture. 

    One possible problem is the low charge current when battery / cap voltage is low (precharge or short).  The current is very low and could take time to charge up cap + battery.  

  • 0 in reply to Bill Johns
    Expert 1110 points

    Hi Bill!

    Good to know, you don't say "no" to the option of charging supercap and batt together,

    "One possible problem is the low charge current when battery / cap voltage is low (precharge or short).  The current is very low and could take time to charge up cap + battery." Precisely about this I was thinking today.

    I will check this. Anyway, the aim is to have the batt as support for a quick start of the system, which in turn is only active while harvesting occurs. In this case, the batt should have charge most of the time, so my theory, provided I can harvest more than I consume... And this is more a wish than a theory...

    Thanks again for pointing me into the good direction.

    Regards,

    Gustavo