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BQ24030 - Li-ion battery not charging

Timz
Prodigy 100 points

Hi,

The voltage at VBAT is 4.2V

RSET is 1.22 k ohm

LDO is 3.3V +/-  0.1V

DPPM is 3.76V

ACPG and USBPG LEDs turn on when connected to respective sources

TS grounded through 10k resistor and voltage is 1V on the 12th PIN

The problem is that battery isn't charging, even though STAT1 LED is always aglow. It just isn't drawing any current. I've also connected battery directly to power supply and it draws current (around 600-800 mA at 6V).

The other issue is that when I connect Load to the output, 2-5 ohm load, it drastically drops the input voltage, say from 5V to 3V, which messes up the entire system. We have a 3.3 V regulator at the output, after which Load is connected.

Any help would be highly appreciated. 

  • 0
    TI__Guru**** 150095 points

    What is the resistance of the cable/trace from the input source to the input to the charger?  Based on your description, it appears that the line is too resistive, causing the input voltage to droop and IC to automatically reduce its output current. 

  • 0 in reply to Jeff F
    Prodigy 100 points

    The wires are fairly thin, so they are not showing any Resistance on the meter.

    At the battery PINS 5,6, the voltage is 4.2V. After attaching a 1uF Capacitor at VBAT terminal, I have connected standard cell phone battery (3.7V), and it is not charging. Although, it charges directly from the power supply, so the battery is not faulty. 

  • 0 in reply to Timz
    TI__Guru**** 150095 points

    The voltage at the BAT pin V(BAT) = battery cell voltage + [the charge current X (the battery resistance + line resistance + connector resistance)].  Once V(BAT) = 4.2V, the IC enters constant voltage mode and the charge current tapers down until the IC terminates charging when the charge current reaches the termination current.   Has the charge current reached the termination current?  

    What is the voltage at the AC and USB pins?  Is there a load on OUT?  What is the voltage on OUT?

  • 0 in reply to Jeff F
    Prodigy 100 points

    The Voltage at AC is through a power supply, so it can vary. I've tried 4V to 8V. (PSEL - High)

    The Voltage at USB pin is 5V, powered through a laptop. (Conditon: PSEL- Low, ISET2- High) 

    Output is through a regulator, so we always get 3.3V. Also, the IC self regulates the output to 6V, no matter how high the input is. So, 6V is the limit.

    Load is a 30 ohm variable resistor. I usually set it around 2-6 ohm.

    According to my calculations, if RSET is 1.22 kohm, the battery should draw around 850mA current and draw less and less as it keeps on charging. But actually, battery is only drawing 30-50mA current, which makes me think that it's stuck in the pre-charge mode. If it is in pre-charge mode, both STAT1 and STAT2 should be aglow, but that is not the case. Status shows that the battery is in Fast Charge Mode.

    The Voltage on PIN 5,6 (which are shorted) is 4.2. The External Battery Voltage is 3.84V and it's not going any further.

  • 0 in reply to Jeff F
    Prodigy 100 points

    Reply, please.

  • 0 in reply to Timz
    TI__Guru**** 150095 points

    If the voltage at pins 5,6 (the BAT pins) is 4.2V, then the IC thinks the battery is charged.  What is creating the voltage drop from the BAT pins to the battery (4.2V-3.84V)?