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Original question:

BQ24650 with no battery

BQ24650: Initiating charge of a fully depleted (0V) LiPo battery.

Dan Slovich
Prodigy 10 points
Part Number: BQ24650

I couple questions:

I have a product that when connecting a fully depleted battery reading 0V is unable to begin charging with the BQ24650 due to a battery not being detected.

1. If I connect a battery at 0V the device will not detect a battery and will not initiate charge. Can I force charging on the device regardless of battery presence and eliminate charge enabling/disabling? 

2. In an attempt to momentarily "trick" the device into detecting a battery, a 10uF capacitor was connected at the SRN node. This caused some boards to momentarily initiate charge long enough for the actual battery to then be recognized and continue charging while others remained in a charge disabled state. It has been about a 50/50 split between success and failure using this approach.

Any suggestions to work around the inability to begin charging a fully depleted battery? Thanks.

 

  • 0
    TI__Mastermind 37205 points

    Hello,

    Can you please send your schematics and input voltage conditions? Also see below from Section 8.3.4:

    "On power-up, if the battery voltage is below the VLOWV threshold, the BQ24650 applies the precharge current to the battery. This feature is intended to revive deeply discharged cells. If the VLOWV threshold is not reached within 30 minutes of initiating precharge, the charger turns off and a FAULT is indicated on the status pins."

    Thanks,

    Mike Emanuel

    Please click "Resolved" if this answered your question.

  • 0 in reply to Michael Emanuel35
    Prodigy 30 points

    Hello Michael,

    I'm Dan's coworker.

    Our battery has a pcm that is opening the battery circuit at around 2.5V and it connects the battery back when it sees voltages grater than 2.5V.

    The  BQ24650 on the boards that aren't able to begin the charge the voltage on SNR are stable at 1.65V while the boards that are able to initiate it it jumps to 4.2V than back to 1.65V  on a high frequency.

    Our RSR is 0.01Ohms, so we should have 400mA pre-charge current, that should be more than enough to bring the battery back, but the voltage needs to hit the 2.5V.

    here is our schematics:

    https://bit.ly/3LGy7ck

    Our Vin is coming from a 20V source.

    Thank you!

  • 0 in reply to Vinicius Fonseca
    TI__Mastermind 37205 points

    Hello,

    Can you please capture waveforms of the input voltage to the converter, the PH node, the charge current, and the SRN node on one plot when each case is happening? Please highlight the switching of the SRN node.

    Can you see what happens when you bypass the battery protector and if it charges the battery? I think the Section 8.3.4 of the previous post may be interfering with the charging operation due to the protector presence.

    Thanks,

    Mike Emanuel

    Please click "Resolved" if this answered your question.