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Charging a Super Capacitor

R4D4
Prodigy 40 points
Other Parts Discussed in Thread: BQ24072

I would like some information on using battery management IC's to charge a supercapacitor and power a small load for a solar panel, while keeping the solar panel output near its maximum power point.  The load has a minimum operating voltage and any power available from the solar panel and not required by the load is to charge the super capacitor.  Please furnish me with information or links to relevant ICs, application notes, circuit details, or appropriate links.  I'm aware of the TI bq2403x family of linear charge regulators but not sufficiently versed to adapt the application.

 

Thanks,

John

  • 0
    TI__Guru 56650 points

    John,

    Would you told me what is input range and output range (supercapacitor fully charging voltage and the minimum system operating voltage)?

    I think you want a battery management IC's which charges a supercapacitor and provides a minimum system operating voltage.  The solar panel is connected on the charge's system bus (bq2403x's out pin).  When charger input power source isn't available, the solar panel and suppercapacitor will power the system.

    Please correct me, if there is any misunderstanding.

    Thanks,

    Wang

  • 0 in reply to Wang5577
    Prodigy 40 points

    Thank you for responding.

    Yes, you understand my requirement.  I would like to use the IC as in Figure 4 of the SLUA394 Application Note,

    http://www.abacus.co.uk/jkcm/cache/fl0018198.pdf

    With the solar panel in place of the AC Adaptor, the super capacitor in place of the battery,

    and no USB port connection.  The solar panel is the charging system.  The solar panel is to

    be kept near its maximum power point and both powers the system, whose current

    demand is variable, and charges the super capacitor.  When the system uses less power

    than the solar cell can provide, the super capacitor is charging; when the system needs more

    power than the solar panel can supply, the system is partially powered by the super capacitor.

    This is a low power project with perhaps a few  100 ma load; no batteries or outside power

    connections.

    The system voltage is variable between 3 and 5 volts; the super capacitor voltage is 5 volts

    Thanks,

    John

  • 0 in reply to R4D4
    TI__Guru 56650 points

    John,

    Because the input comes from the solar panel only and there is no USB port connection. So, the bq24072/3/4/5 will be better. http://focus.ti.com/lit/ds/symlink/bq24072.pdf

    At beginning, bq2407x was designed for Li-ion battery charger application. So, it sets a pre-charge battery voltage threshold. If the battery voltage is lower than 3V, the charge current will be reduced to Ichg/10.

    For example, if set fast charge current limit at 1A, when suppercap voltage is lower than 3V, the suppercap only get 0.1A charging current.

    This is a trade-off, if we want higher charging current at low voltage, we need set higher fast charge current. 

    Regards,

    Wang

  • 0 in reply to Wang5577
    Prodigy 50 points

    Hi Wang,

                      My Project comprise of a Solar Panel (4.8V, 100mA), Super Capacitor and Permanent Battery. I was looking for a Solar charger that can trickle charge the Super Capacitor (3.95 max charge voltage and 100mA max charge current) and also if possible can have an in built primary switch/ guage that can be connected to a primary permanent battery. Thus whenever enough sunlight is falling on the solar panels the super capacitor is being charged and supports the load. If there is no or small amount of sunlight not enough to charge the Super Capacitor then the charger should be capable enough to switch the output from the Permanent battery to support the trickle charge of the Super capacitor. Other wise I may need to add a switch/ gas guage to monitor the solar charger output and whenever it falls below a certain threshold need to switch it to the permanent battery to trickle charge the Super Capacitor.

    Please recommend me whether bq2407x shall work or else do you have some other smart chargers that can be used along with the Permanent Battery. Awaiting your response.

    Also can the charger decrease the charge current from 100mA to 20mA if the temp goes beyond the range < -20C  and > 60C

    Regards

    Syed Haq