Asus X512F won't hold on battery charge

[Kambi13]

Hi all, need some help on this matter. Laptop works fine plugged in, battery still has 80% charge and won't go above that value, and as soon I remove power it won't hold on battery charge and turns off.
Now on Battery + it has 8,37V, which is roughly the rating for the battery pack, but it should be higher. IC Charger is BQ24780S, BATDRV and BATSRC, both measure those 8,37V, but when I probe them they start with 11,53V and drop immediately to 8,37V.
Checked the battery mosfets both High Side and Low Side (N-Channel) and they seem ok. Even replaced them to be sure. So my best guess is that the IC charger is faulty.

Best regards all

[mon2]

Re: Asus X512F won't hold on battery charge

Measure the voltage to ground on each pin of the battery connector. Specifically interested in the readings for the SCL / SDA lines which may be stuck.

It is very possible that the battery is also defective. Have you tested with another? Consider to source another one from Amazon for testing and return it if it does not work for you. The return policy is great from Amazon.

[Stevedb]

Re: Asus X512F won't hold on battery charge

Did you check the first and second mosfet. How much do you have at gate from the first and secont mosfet ( ac drive)

[Kambi13]

Re: Asus X512F won't hold on battery charge

Hi mon, SCL / SCA both measure 3.24v and jumping to 3.28v, going back and forth
BAT + 8.31V

[Kambi13]

Re: Asus X512F won't hold on battery charge

Hi Steve. ACDRV has 24.43V

[mon2]

Re: Asus X512F won't hold on battery charge

Both the SMBUS and ACDRV are good voltages.

Suggest to carefully measure the voltage to ground of each pin on the charger IC.

Post your list with the pin numbers for a review. Do connect your battery and power adapter.

[Kambi13]

Re: Asus X512F won't hold on battery charge

Here it goes

1 - ACN -> 19,49v
2 - ACP -> 19,49v
3 - CMSRC -> 19,02v
4 - ACDRV -> 24,44v
5 - ACOK -> 5,95v
6 - ACDET -> 2,659v
7 - IADP -> 6mv
8 - IDCHG -> 4,5mv
9 - PMON -> 4,6mv
10 - PROCHOT -> 0v
11 - SDA -> 3,24v
12 - SCL -> 3,24v
13 - CMPIN -> 255mv
14 - CMPOUT -> 6v
15 - BATPRESS -> 4,4mv
16 - TB_STAT -> 9,6mv
17 - BATSRC -> 8,31v
18 - BATDRV -> 8,31v
19 - SRN -> 8,31v
20 - SRP -> 8,31v
21 - ILIM -> 1,171v
22 - GND
23 - LODRV -> 18,4mv
24 - REGN -> 6v
25 - BTST -> 12,90v
26 - HIDRV -> 8,33
27 - PHASE -> 8,31
28 - VCC -> 19,16v

[mon2]

Re: Asus X512F won't hold on battery charge

1 - ACN -> 18,49v
2 - ACP -> 19,49v

Something is wrong here. This is too much of a voltage drop. Remove all power.

Meter in the lowest resistance mode.

One meter probe on ACN. Other meter probe on ACP.

What is the resistance ?

[Kambi13]

Re: Asus X512F won't hold on battery charge

Sorry both ACN and ACP measure 19,49v. Resistance between is 1.1 Ohms

[mon2]

Re: Asus X512F won't hold on battery charge

Can you short your meter probes and post the measurement?

The 1R1 ohms sounds high for a current sense resistor. Often the current sensor resistors are 10 milli-ohms.

[Kambi13]

Re: Asus X512F won't hold on battery charge

Ok will do, post tomorrow. Thank you so much

[Kambi13]

Re: Asus X512F won't hold on battery charge

Good Morning here, back to business, so my probes shorted are at 0.00 Ohms, however as I haven't been able to find here where I live some good needle probes the reading I've taken is one probe at the leg of the IC and the other one at the nearest cap, so there could be some slight difference there.

[Kambi13]

Re: Asus X512F won't hold on battery charge

Probes shorted read 0.00 Ohms, however as I haven't been able to find here where I live some good needle probes the reading I've taken is one probe at the leg of the IC and the other one at the nearest cap, so it could be some slight difference there.

[Kambi13]

Re: Asus X512F won't hold on battery charge

Any other thoughts on this matter?

[mon2]

Re: Asus X512F won't hold on battery charge

As we do not have the schematic, cannot be sure of the current sense resistor values being measured between ACN and ACP pins. The 1R1 reading seems too high for this component.

Can you check the resistance between SRN and SRP pins? Post the measurement. No power while checking the resistance. This resistor is used to monitor the current draw of the battery pack.

Post a close up pic of the area of the charger IC with the ACP and ACN pins. The current sense resistor should be close by.

[mon2]

Re: Asus X512F won't hold on battery charge

Also, double check the voltage to ground of pin #3 in your posted list (cmsrc). It is too low.

There will be a resistor between this pin #3 and the dcin mosfets. Typically this resistor is expected to be ~4k ohms.

After checking the voltage, remove all power. Meter in resistance mode.

One meter probe to pin #3 pin of this charger IC. Other meter probe to the source pin of the DCin mosfets. Repeat with probing the drain pins. One of these checks must be a stable ~4k ohms else the resistor is likely defective.

[Kambi13]

Re: Asus X512F won't hold on battery charge

Resistance between SRP and SRN 20,04 Ohms
CMRSC still 19,02V
Resistance between Pin 3 (CMSRC) and the source of the DC In Mosfets - 4,02k wich is about right, between pin 3 and drain 180k on the first Mosfet and 7,72k on the second

[mon2]

Re: Asus X512F won't hold on battery charge

Resistance between SRP and SRN 20,04 Ohms

This sounds really high for a current sense resistor. Remove all power.

Meter in lowest resistance scale. Connect one meter probe to SRN.

Other meter probe to the closest resistor you can find. We are hunting for the current sense resistor and the resistance between these 2 points should be ~0 ohms.

Once it is found, continue to test the OTHER side of this resistor. Meter this time on SRP pin of the charger IC and other meter probe to the opposite side of the found resistor.

Again, the resistance should be ~0 ohms.

Finally, apply the meter probes directly across this found resistor. What is the resistance of this current sense resistor ? Is it still ~20 ohms ?

Post a picture of the part for a review.

[Kambi13]

Re: Asus X512F won't hold on battery charge

Hi again mon2, see the attached picture. The closest resistors to SRN and SRP are both 10 Ohms.
Now if you're looking for the current sense resistor for the battery, from SRN and SRP to both sides of that 0 Ohm resistor, there's still those 10 Ohms before and after the current sense resistor

[mon2]

Re: Asus X512F won't hold on battery charge

The resistor with R010 markings = 10 milli-ohms = 10/1000 ohms.

Let me try to trace the path which may make sense if they have additional resistors in the current sense loop.

Update:

In reviewing other boardview files for Asus motherboards, they do indeed like to place 10 ohm resistors in series with each pin of the SRN and SRP for a total of 20 ohms extra in the current sense path.

So total resistance between SRN & SRP = 10 ohms + current sense resistor (10 mOhms) + 10 ohms = ~20 ohms as you have measured. This leg appears to be ok.