Asus X415EA not charging battery

[johnbeton]

Hello,

I have an Asus X415EA board that is not charging the battery after some liquid damage. Everything else works, except charging the battery.
So far I measured all the pins on the bq24780s controller with the following result:

1. ACN = 0.0V
2. ACP = 19.02V
3. CMSRC = 18.5V
4. ACDRV = 23.9V
5. ACOK = 5.9V
6. ACDET = 2.57V
7. IADP = 0.17V
8. IDCHG = 0V
9. PMON = ?
10. PROCHOT = 5.05V
11. SDA = 3.3V
12. SCL = 3.3V
13. CMPIN = 0.47V
14. CMPOUT = 6.0V
15. BATPRES = 0.0V
16. TB_STAT = 3.38V
17. BATSRC = 0.9V (after +/- 25 seconds = 0.23V)
18. BATDRV = 0.93V (after +/- 25 seconds = 0.27V)
19. SRN = 0.9V (after +/- 25 seconds = 0.23V)
20. SRP = 0.9V (after +/- 25 seconds = 0.23V)
21. ILIM = 1.16V
22. GND
23. LODRV = 0.0V
24. REGN = 6.0V
25. BTST = 5.87V
26. HIDRV = 0.9V (after +/- 25 seconds = 0.23V)
27. PHASE = 0.9V (after +/- 25 seconds = 0.23V)
28. VCC = 18.74V

The highside and lowside mosfet don't seem to be shorted or defective.
I also tried another battery with no result

If someone has an idea what I can check, I would appreciate all the help, still learning on these charging circuits.

[mon2]

Pins 1 & 2 should be the same voltage. Pin 1 pcb trace (ACN) is broken. Fix it to fix the issue.

[johnbeton]

i'm sorry, I checked again, and PIN1 is also 19.02V, i must have made an error in my first measurement.

[mon2]

Ok.

2. ACP = 19.02V
3. CMSRC = 18.5V

CMSRC is a measurement between the 2 x DCin mosfets so the voltage here should be equal to the voltage @ ACP/ACN junctions.

Confirm the resistance of the series resistor that will be on the CMSRC pin and mates with the DCin mosfets. Check the datasheet for this charger IC to compare notes on what Asus has most likely used for this logic board.

[DeXXter]

Did u check the first mosfets? A failure there can trigger charging issues too. Is your ec fine? no water there?

[johnbeton]

The resistor is 4.02KOhms, I have 19V on pin 1 and 18.55V on pin 2

I checked the first mosfets for short, but they are not short. There was no water in the area of the EC.

[mon2]

Remove all power. Measure the resistance between pins 1 & 2 - directly at the charger IC.

Repeat for the SRN / SRP pins. What are the measurements in ohms? Comparing to the schematic values. Need to confirm the full path resistance for the current sense loop circuit is within specs.

[m1ch43lzm]

Hi, I would check the traces going to the following pins
From the BQ24780S datasheet:

BATSRC, 17
Connect to the source of N-channel BATFET. BATDRV voltage is 6 V above BATSRC to turn on BATFET.

BATDRV, 18
Charge pump output to drive N-channel MOSFET between battery and system (BATFET). BATDRV voltage is 6 Vabove BATSRC to turn on BATFET and power system from battery. BATDRV is shorted to BATSRC to turn off BATFET. Place a 4-kΩ resistor from BATDRV to the gate of BATFET limits the inrush current on BATDRV pin.

SRN, 19
Charge current sense resistor negative input. SRN pin is for battery voltage sensing as well. Connect SRN pin with a 0.1-µF ceramic capacitor to GND for common-mode filtering. Connect a 0.1-µF ceramic capacitor from SRP to SRN to provide differential mode filtering.

SRP, 20
Charge current sense resistor positive input. Connect a 0.1-µF ceramic capacitor from SRP to SRN to provide differential mode filtering.

LODRV, 23
Low-side power MOSFET driver output. Connect to low-side N-channel MOSFET gate

HIDRV, 26
High-side power MOSFET driver output. Connect to the high side N-channel MOSFET gate.

PHASE, 27
High-side power MOSFET driver source. Connect to the source of the high-side N-channel MOSFET.

You should get battery voltage at pin 17, check the 10ohm resistor and the trace going to it from pin 17

Pins 19,20, same, around battery voltage, through 2 10ohm resistors, check resistors and traces
Measure resistance between pins 19 and 20, you should get 20ohms

Pin 27, you should get battery voltage

Schematics/boardview
https://www.badcaps.net/forum/troubl...c-or-boardview
I'm looking at the X421 schematics posted there
SN2867 = BQ24780S

[johnbeton]

Resistance between pin 1 & 2 on charger IC = 1.1 Ohm
Resistance between SRN & SRP on charger IC = 21.2 Ohm

PR8968 = 10.4Ohm

Thanks for the link to boardview

[m1ch43lzm]

Measure voltage at the current sense resistor PRS8903 with the battery plugged in, you should get the battery voltage

If not, remove all power, measure continuity from the + on the battery connector on the board to PRS8903, also check PJP8901 if available on your board (can't check board view right now, I'm on my phone), should be closed with a solder blob

[johnbeton]

Both batteries are completely empty.
The resistance from the + pin to PRS8903 is 1.1 Ohm on one side, 11.1 Ohm on the other side.
PJP8901 is present and is indeed a solder blob.

Edit: one thing I noticed on PD8900 I have 19V on Pin 2 and 3, and 2.9V on Pin 1. Don't know if this is normal ?

[alfredposadas08]

make sure the dc in mosfets are fully switched

[johnbeton]

make sure the dc in mosfets are fully switched

I checked them on shorts, but no shorts, and have 19V past botch mosfets, is this ok ?

[mon2]

Need the actual mosfet resistance measurements of the high side and low side battery mosfets.

Source / drain
source / gate
Gate / drain

Post each measurement in ohms.

[johnbeton]

Highside
Source / drain (black probe on drain) = starts at 2.89 MOhm and going up while I measure
Source / drain (red probe on drain) = 0.00 Ohm
source / gate = 9.9 KOhm
Gate / drain = 1.4 MOhm and going up while I measure

Lowside
Source / drain = 4.9 MOhm
source / gate = 0.21 MOhm
Gate / drain = 1.8 MOhm and going up while I measure

[mon2]

Source / drain (red probe on drain) = 0.00 Ohm
source / gate = 9.9 KOhm

High side mosfet is defective. Must be replaced. Suggest to also replace lowside mosfet for safety.

[johnbeton]

I removed the mosfets and checked them off the board, they seem to be fine, but just to be sure, I replaced them with equivalent mosfets, but the problem remains.
Maybe the controller itself is bad ? I have a donor board with the same controller, I could try exchange the controller.

[mon2]

How fine are they? Need the actual measurements.

[johnbeton]

With black probe on drain and red probe on source I have 9,89 KOhm on 1 mosfet, and 11,73 KOhm on the other mosfet.
All other combinations (reverse probes, source - gate, drain - gate, ....) are OL.

I also tested in diode mode:
Black probe on drain, red probe on gate. Then black on drain, red on source gives 0 Ohm.
Put black probe on gate, closes the mosfet.