Asus X541 charging issue

[IamPritesh]

So we have a asus x541 board which does not charge the battery. Tried replacing the battery with a known good battery. Also replaced the charging IC and still no luck.

The charging IC is bq24780S and here are the measurements with no battery attached.

The laptop is working fine except for the battery getting charged. The charging led keeps blinking amber.

[mon2]

Re: Asus X541 charging issue

What is the voltage to ground on pin # 15 of the charger IC ?

Be sure the battery connector is OK with the battery pack. Do you have any charge on the battery pack(s) you have tested ?

Does that battery voltage appear onto the battery mosfet pins ?

[IamPritesh]

Re: Asus X541 charging issue

Both the unused batteries have no voltage which could possibly because they have been sitting idle for several months at the store. I think even when there is no battery we should still get some voltage on the charging coil even when battery is not connected. There is no gate voltage on the mosfets. The mosfets seems to be OK. I forgot to take the measurement of pin 15 ( will do that tommorow)

[mon2]

Re: Asus X541 charging issue

When the battery is connected, the battery present status will be used by the charger IC to note that the battery is connected -> then enable the battery mosfet -> the charge voltage should be present on the battery connector.

The battery charge voltage will be dialed up by the high side and low side mosfets which accept the main ~20 volts but will be a lower voltage for the battery pack (acting like a buck regulator). Without a battery presence signal, would not expect a charge voltage on the battery connector.

[IamPritesh]

Re: Asus X541 charging issue

What is the voltage to ground on pin # 15 of the charger IC ?

Be sure the battery connector is OK with the battery pack. Do you have any charge on the battery pack(s) you have tested ?

Does that battery voltage appear onto the battery mosfet pins ?

When the battery is connected, the battery present status will be used by the charger IC to note that the battery is connected -> then enable the battery mosfet -> the charge voltage should be present on the battery connector.


The battery charge voltage will be dialed up by the high side and low side mosfets which accept the main ~20 volts but will be a lower voltage for the battery pack (acting like a buck regulator). Without a battery presence signal, would not expect a charge voltage on the battery connector.

Pin 15 of the charger IC has no voltage with and without battery.

Battery connector without battery measurement :

Pin 1 ( BAT CON) ------> OV
Pin 2 ( BAT CON) ------> OV
Pin 3 P_RTC_LDO3V3 ------> 2.7
pin 4 BAT_EN# ------->0 V
pin 5 SMB0_DAT_CLK_CON ------> 3.2
pin 6 SMB0_DAT_BAT_CON ------> 3.2
pin 7 TS1#_BAT_CON ------> 0.9V


Battery connector with battery measurement :

Pin 1 ( BAT CON) ------> OV
Pin 2 ( BAT CON) ------> OV
Pin 3 P_RTC_LDO3V3 ------> 2.9
pin 4 BAT_EN# ------->0 V
pin 5 SMB0_DAT_CLK_CON ------> 3.2
pin 6 SMB0_DAT_BAT_CON ------> 3.2
pin 7 TS1#_BAT_CON ------> 0V

[mon2]

Re: Asus X541 charging issue

Based on the logic low status of battery connector pin #4, the charger should always be sending out a charge voltage. The charger voltage may be 0 volts due to a shorting condition or bad charge mosfets.

Remove all power / no battery.

Check the resistance to ground of the battery connector pins #1 and #2. Post the readings. Confirm the resistance to ground is the same at the inductor on this same rail.

Next, check the resistance across the high side mosfet of the charger circuit used by the battery.

See figure 16 and locate the hidrv mosfet. You can use this datasheet for the pin numbers.

The high side and also low side mosfets must be working to dial up a voltage for the battery pack.

Check:

Source & drain
Source & gate
Gate & drain

Post each measurement. Repeat for the low side mosfet.

[eduardsk]

Hello. I know it is probably late but this may help other people. That "pin 4 BAT_EN# ------->0 V" is getting the ground from a screw located on top of the board, near the battery connector. The screw is connecting two pads together, pin4 and ground. Without the screw or other type of connection the charging will never start.