Hello, I have an Asus ROG Zephyrus G14 GA401QM which had a short circuit in the BQ24800 and would not turn on. The BQ24800 was replaced and now it turns on with the charger, but does not charge the battery. I have schematics and boardview, I checked mosfets and basic signals, but everything seems to be fine. The output voltage to the battery does not exceed 1V
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Are you using the original and recommended power adapter with the proper ratings? If the adapter is underpowered, the battery will not charge and the CPU will be throttled.
Carefully measure the voltage to ground of the following battery connections:
P_SMB0_CLK
P_SMB0_DAT
Post each measurement. -
Yes, I am using the original adapter, and I am also injecting adequate voltage, with amperage similar to that of the original adapter.Originally posted by mon2 View Post
The measurements are as follows:
P_SMB0_CLK = 3.3V
P_SMB0_DAT = 3.3V
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DC-in mosfet.pin4 voltage?
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the voltage on pin 4 of mosfet DC-in is =25VOriginally posted by mcplslg123 View Post
voltage for high Mosfet on Bat+ =0.9V
I measured all the mosfets to check for short circuit and they are fine.Comment
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DCin mosfet gate voltage is fine to enable the power path.
The battery charge voltage will be defined by the high side mosfet @ PQH8901 and the low side mosfet @ PQL8901.
Remove all power. Measure the resistance across the high side mosfet @ PQH8901.
Measure:
source / drain
source / gate
gate / drain
Post each measurement. Repeat for PQL8901.
The ~19v adapter voltage travels onto the main power rail -> then these 2 mosfets are used to switch on / off to dial down the voltage for the battery to charge by the charger IC.
Also interested in the voltage to ground on pin # 1 and # 2 on the charger IC.Comment
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PQH8901Originally posted by mon2 View Post
Source (Red) / Drain (Black) = 0.65 Mohm
Source(Black) / Drain (Red) = 0.7 Mohm
Source (Red) / Gate (Black) = 180Kohm
Source (Black) / Gate (Red) = 180Kohm
Gate (Red) / Drain (Black) = 700Mohm
Gate (Black) / Drain (Red) = 0.82Mohm
PQL8901
Source (Red) / Drain (Black) = 0.600Mohm
Source(Black) / Drain (Red) = 0.700Mohm
Source (Red) / Gate (Black) = 8.3Kohm
Source (Black) / Gate (Red) = 113Kohm
Gate (Red) / Drain (Black) = 0.750Mohm
Gate (Black) / Drain (Red) = 0.850Mohm
Pin 1=20V
Pin 2=20VComment
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Flux and remove PQL8901. This mosfet has low resistance. Then measure it again when it is out of circuit on your desk. Do not power up without this mosfet. Very likely this mosfet is defective. The high side may also be bad with the 180k ohms but for now, suggest to replace the low side mosfet.Comment
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I measured the mosfets from the outside, and they have normal values, there is no low resistance, nor short circuit.Originally posted by mon2 View Post
The measurements between source and gate, remain low on the motherboard, for both mosfetsComment
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Test with another known good battery. Try Amazon. You can always return the battery if it is not required. It is possible that the battery is locked and this condition is reported to the charger IC over the SMBUS. For the same reason, the battery voltage is kept low.Comment
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The strange thing is that the battery worked until it died, and that's when they decided to repair it because the charging LED no longer lit up. But I'll see if I can try another battery that I know works well.Originally posted by mon2 View PostComment
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I ordered another battery from Amazon, put it in and it showed the same problem:Originally posted by mon2 View Post
-battery LED blinks
-same voltages as I mentioned
the voltage on pin 4 of mosfet DC-in is =25V
voltage for high Mosfet on Bat+ =0.9V
-battery in windows shows 100% charge (obviously when disconnecting the charger it turns off by itself)
-the laptop turns on by itself
I should order a brand new BQ2400 from AliexpressComment
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