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BQ24650: BQ24650

Dinesh Nimone
Prodigy 10 points
Part Number: BQ24650

Dear sir, 

      I want to charge Orange 18650 Li-on Battery pack 6 cell , 22.2v, 3c, 10,000mAh by using  BQ24650 for 1A charge current, I am using all Resistor capacitor components as per TI datasheet instead of MOSFET Si7288 . When battery get fully charge up to regulation voltage and If I connect or disconnect fully charge battery then BQ24650 IC burn and either LOW side MOSFET or HIGH SIDE MOSFET(IRF7470 used in my My application circuit) get also damaged. To charge 22.2 volt battery and avoid damage charging IC can you suggest components for 22.2v battery charging circuit.

    

And What is function of Q3, CE  bar active low signal in typical application.

I have adjusted MPPT , battery Regulation voltage , As per battery charging 22.2 voltage.

  • 0
    TI__Mastermind 40535 points

    Hello,

    I need a schematic to fully evaluate your setup. Also, does this only happen when unplugging or plugging in a battery (are you able to have normal operation otherwise)? You may need some circuit to protect against the inrush of hot plugging the battery.

    Q3 is used to disable charge by pulling MPPSET to GND.

    Regards,

    Mike Emanuel

  • 0 in reply to Michael Emanuel35
    Prodigy 10 points

    1.I have attached schematic for evaluate setup. 
    2.Charging IC and MOSFET damaged when connected fully charge up to (21.V) battery, to battery pack point.
    3.Next day I have discharged battery At 9V and exchanged with new Charging IC on board.
    4.Again start for charging it charged up to 21.8 volt in 7 hr at 1 amp charge current. now disconnected power supply and battery from circuit.
    5. Next day connected battery(checked voltage was 21.8) to charging circuit (power supply was not connected) then suddenly big spark occurred on board and found charging IC is again damaged and MOSFET is also damaged.

    which circuit may need to protect against the inrush of hot plugging the battery.

  • 0 in reply to Dinesh Nimone
    TI__Mastermind 40535 points

    Hello,

    The schematic looks fine.

    However there is one thing. The MPPSET voltage is 22 V and the max charge voltage is 23.1 V. When the charger starts to collapse the solar panel, it will pull it below the nearly charged battery voltage (to MPPSET of 22 V) stopping charge. As this is a buck converter, the input voltage must always be greater than the output voltage.

    Please capture the SRN voltage when plugging in the battery. I suspect the hot plug is causing ringing above the Recommended ratings of the SRN and/or more pins. If this is the issue, you need to mitigate inrush current and the transient induced by hot plugging the battery. Please see below recommendations:

    https://www.ti.com/lit/eb/slyy168/slyy168.pdf

    https://www.ti.com/lit/an/slva670a/slva670a.pdf

     Regards,

    Mike Emanuel

  • 0 in reply to Michael Emanuel35
    Prodigy 10 points

    1.Now I have set the MPPT volt at 23.8v (more than  battery volt regulation volt 23.1v) by changing R103 with 510K, Here we can't set battery volt regulation exact  at 22.2 due to unavailability components, Now I am going to charge battery 23.1v(As per battery specification battery can charge up to 25v). 

    2.Before moving towards hot plugging i want discuss about MOSFET, In Schematic i am using MOSFET Q100 and Q101 is IRF7470 which is having lower Gate to source voltage ie +/-12volt and as per  Texas application circuit Si7288 having gate to source voltage is +/-20v. does it affect to damage of MOSFET?

    3Updated schematic For MPPT 23.8v

    please help.

  • 0 in reply to Dinesh Nimone
    TI__Mastermind 40535 points

    Hi,

    I just wanted to confirm something. Is 23.8 V the actual MPPT voltage of the solar panel? You want to design the MPPSET pin such that it matches the MPPT voltage of the panel. Otherwise, you are not converting the solar energy to the maximum efficiency.

    Verified MPPT voltage at 23.87 V.

    With your new MPPT voltage and battery voltage you are operating very close to the SLEEP threshold. I would recommend a larger margin between the max battery voltage and the MPPT voltage.

    The IC is designed for 6 V of gate drive voltage so +/- 12 V vs +/- 20 V should be fine. However, please test according to your application.

    Regards,

    Mike Emanuel

  • 0 in reply to Michael Emanuel35
    Prodigy 10 points

    Thank you sir,

    1.To charge battery, i am using DC 28v External power supply instead of solar panel, so what should be MPPT for DC 28v External power supply.
    2.And thank you for solved MOSFET related quarry.
    3.Now I moving towards the hot plugging.

    4.as per Texas Instruments datasheet, is it important to connect The maximum output capacitor Cmax, shown below photo. 

    If important then what should be the capacitance value. voltage for battery volt regulation volt 23.1v ?

  • 0 in reply to Dinesh Nimone
    TI__Mastermind 40535 points

    Hello,

    1. In the case of using an external power supply, you only need to make sure the power supply voltage is always above the MPPSET setting. Please control the input voltage as 28 V is the maximum recommended input voltage.

    4. According to Equation 9 and 10 in this example you require the output capacitance to be less than 2000 uF. In fact, in Table 1, we recommend 10 uF for 1 A charge current. We do not recommend connecting the maximum capacitance as shown by the equations, as this could put you into a mode where a battery is detected when there is not one.

    Regards,

    Mike Emanuel