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BQ33100: BQ33100 solution for high amp charging?

Chris Jones25
Prodigy 220 points
Part Number: BQ33100
Other Parts Discussed in Thread: BQ24640

I'm using 5 x 350F supercaps in parallel with a 12V PC power supply (1200W) for powering multiple high current motor controllers. The power supply can handle the motors once they are moving but at motor startup the current draw exceeds what the power supply can handle. I'm having some issues with my current design which uses an ALD810025 for capacitor balancing and a MOSFET driving a 500A contactor/relay that switches between a direct connection to the caps and a pre-charge resistor (to limit current draw when cap voltage is low). 

An Arduino is used to measure supercap stack voltage and decide when to turn the relay/contactor on. Is there a solution with the BQ33100 that can charge at 20-30A while allowing pull current to be pulled from the supercaps? 

  • 0
    TI__Genius 10830 points
    hi Chris,
    bq24640 is our best charger for 20A (not for 30A though).
    www.ti.com/.../BQ24640

    Regards,
    David
  • 0 in reply to David Hien
    Prodigy 220 points
    Will that also limit the current that can be drawn from the supercaps to 20A? How much voltage drop is there through the bq24640? With a 12V power supply will I be able to charge the caps to 12V? My application has the caps in parallel to the power supply and if the voltage of the caps is too low they won't end up being used.
  • 0 in reply to Chris Jones25
    TI__Mastermind 20570 points

    Hello Chris,

    Could you please start a new post regarding on bq24640. Please include bq24640 in the title name.

    The bq24640 is a buck charging controller. This means the input voltage needs to be higher than the output voltage.

    Below is the description from the datatsheet.

    "For proper operation of bq24640, VCC must be from 5 V to 28 V. To begin charging, VCC must be higher than SRN by at least 500 mV (otherwise, the device will be in sleep mode). TI recommends an input voltage of at least 1.5 V to 2 V higher than the super capacitor voltage, taking into consideration the DC losses in the highside FET (Rdson), inductor (DCR), the input diode drop, and current-sense resistor (between SRP and SRN). Power limit for the input supply must be greater than the maximum power required for super capacitor charging."

  • 0 in reply to Jing Zou
    Prodigy 220 points

    I'm considering using the BQ33100 for just cell balancing and removing the BQ24640 and replacing it with a large panel resistor to limit in-rush to the supercaps at low voltage. 

    If I don't need charge control from the BQ33100 can I leave CHG, CHGLVL0, and CHGLVL1 floating? In the BQ33100 document http://www.ti.com/lit/ug/sluu466/sluu466.pdf  Figure 8 has a charge control circuit, specifically Q1 and Q6. Can those be removed if I'm not doing charge control? I always want to charge at 12V, I have no need to ever charge at 10.5 or 11V. I'm using 5 x 2.7V which gives me 13.5V, so 1.5V headroom. 

  • 0 in reply to Chris Jones25
    Prodigy 220 points

    Any thoughts on my last message? 

  • 0 in reply to Chris Jones25
    Prodigy 220 points
    I'm going to start a new post. Not sure why I can't get an answer on this question after a week.
  • 0 in reply to Chris Jones25
    TI__Mastermind 20570 points
    Hello Chris,
    The bq33100 and bq24640 are supported by different team. That is why I will not received notification on your post regarding on bq24640 in this post thread. Regarding your question on BQ33100, someone from Dave's team should be able to help.