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BQ24610: Use without a battery attached

robin corn
Prodigy 200 points
Part Number: BQ24610


Hello,

We are using the BQ24610 on our PCB. But we would like to be able to use this PCB with and without a battery. It is working (almost) perfectly with a battery attached but when we detatch the battery, the system starts switching on and off all the time.

It seems like this is caused by the absence of the battery and the BQ24610 trying to detect a battery. Is there a way to switch off the battery driver when there is no battery attached? Such that we can use our system without a battery. We were thinking about putting a shunt between the CE pin and the VREF pin. Then we will connect the two when there is a battery present and disconnect the two when there is no battery.

A last problem that we have is that when we attach a deeply discharged battery it will not charge at all. There is no current, while the BQ24610 should get in precharge mode and draw 0.3A of current. I have attached our schematic.

  • 0
    Prodigy 200 points

    In the above image i forgot to draw one resistor, I have added it in the image below

  • 0
    TI__Genius 10385 points

    Robin,

    Based on you observation I agree with you that the battery detection routine is the cause. I think your idea of introducing a shunt will work well as the device has an internal pulldown resistor.

    What is your desired VLOWV threshold for your application?

    Thanks,

    Ricardo

  • 0 in reply to Ricardo
    Prodigy 200 points

    Dear Ricardo,

    Thank you for your response. If we understand it correctly the VLOWV doesn't seem to be the problem. The VLOWV treshold is where we go from precharge to fast charge. It should be lower than 18V because 18-26v is the range in which we use the 6 cel battery.

    Instead we would like to understand why there is no charge current at all when we attach a 26V charger and a deeply discharged battery (Which measures 7V).

  • 0 in reply to robin corn
    TI__Genius 10385 points

    Robin,

    Sorry for the misunderstanding. That was my fault. Let's step through section 9.3.7 and make sure charging can be enabled. I have emphasized the measurements I need from you in bold.

    Thanks,

    Ricardo

    The following conditions must be valid before charge is enabled:

    • CE is HIGH.

    Confirmed good

    • The device is not in undervoltage lockout (UVLO) and not in VCCLOWV mode.

    Assuming 26V adapter is good, confirm with /PG signal going low

    • The device is not in SLEEP mode.

    confirm with /PG signal going low

    • The VCC voltage is lower than the AC overvoltage threshold (VCC < VACOV).

    Please verify on the VCC pin with a DMM

    • 30-ms delay is complete after initial power up.

    Assuming this is not it

    • The REGN LDO and VREF LDO voltages are at the correct levels.

    Please confirm with DMM

    • Thermal shut (TSHUT) is not valid.

    Assuming this is not it

    • TS fault is not detected.

    This should not be it