BQ24600: RRC Battery not charging

Hello Yan,

In order to assist with debug I need some more measurements.

What is the value of VFB when this is happening?

Can you please include a waveform of the input voltage, Q44A gate, PG, and STAT?

In addition, can you please include a waveform of the input voltage, battery voltage, PH voltage, and charge current?

Regards,

Mike Emanuel

Hello Mike,

Thanks for answering me.

VFB = 2.1V

On the bottom of each scope, you have measures done on each signal like min value, max value and mean value.

Please find below the waveforms of the Input Voltage, Q44A Gate, PG/ and STAT :

C1 - Yellow- : Input Voltage
C2 - Red - : Q44A Gate
C3 - Blue - : PG/
C4 - Green- : STAT

Please find below the waveforms of the Input Voltage, Battery Voltage, PH Voltage and Charge Current :

C1 - Yellow- : Input Voltage
C2 - Red - : VBAT
C3 - Blue - : PH
C4 - Green- : Charge Current

As we can see, there is no current charge at all
However, the blue signal is adding some noise on the others signals.

On the following scope, I retired the blue signal :

Finally, please find the scope of the PH Voltage zoomed In :

Regards,

Yan

Hi Yan,

I have several things for you.

1. If VFB is 2.1 V, charge is complete. The regulation voltage for the VFB pin is 2.1 V. Have you double checked your regulation point? What is your applied battery voltage and what is your designed charge voltage regulation? You state that max voltage is 16.4 V setting, but one waveform shows a max of 17.23 V.

2. The STAT pin only blinks at 0.5 Hz for "charge suspend, timer fault, input overvoltage, battery absent." Charge suspend relates to the TS pin. Has your charge timer expired? I do not see you exceeding 28 V on the input. You confirmed you have a battery attached?

3. The input signal looks clean, always connected.

Regards,

Mike Emanuel

Hi Mike,

1. For the battery voltage, refer to the Figure 3 because I have some noise on the Figure 2. As you can see, VbatMAX = 16.63V because of the little spike when the voltage is rising. When stable, Vbat = 16.41V.
However, the optimal recharge voltage for the RRC battery is 16.8V. So I tried others couples of resistors to be around 16.8V, but it did not solve my problem.
I am waiting for +/-0.1% resistors to resume my tests.

2. I confirm I have a battery attached. Otherwise I would have 0V on Vbat when the BQ24600 is not trying to recharge the battery -see Figure 2 and 3-. What is the charge timer?

Regards,

Yan

Hi Yan,

Looking at your schematic, your maximum voltage regulation of the battery is 16.4 V and your recharge voltage is 16.0 V. If you are applying at or over 16.4 V you are on the edge of CV mode or just in over-voltage of the battery. Please confirm the FB resistors of the charger. For the timer, check out the "Safety Timer" in the Electrical Characteristics Table. 

Regards,

Mike Emanuel

Hello Mike,

As I said in my first message, VchargeMAX = 16.8V.
According the RRC battery datasheet, the over-voltage protection is activated when Vcharge = 17.08V when temperature is between 10 and 50°C.

I confirm R202 = 150kΩ and R204 = 22kΩ.

I also checked the charge timer : every time I am testing the BQ24600, I just let the battery connected for a few minutes, so the charge timer had not expired.

I guess the problem comes from the RRC battery.
I will contact you if I find something new.

Regards,
Yan

Hi Yan,

Keep me posted.

Regards,

Mike Emanuel