Alienware 17 R4 LA-D751P - Battery Not Charging

[hobostove]

Was water damaged (pint of beer). I've been messing with it and it's mostly up, but there's an issue with the battery not charging.

The original was DoA, so there's a new one in there now. On the bench psu, measuring the battery connector (battery is 15.2V), the connector shows 16V and 9A on the 19.5v psu!

This lasts a second or two, then it settles down to 14V, 0.06A. Unplugging AC power and it shows 13.5V. Do we think battery or board (BQ, Mosfet, etc)?

Link to schematic

[FriedFred]

I think 9 Ampere is absolutely not normal as a charging current. Usually, it starts with a testing sequence, and a little current. After the raising voltage is detected, the current will be raised up to a nominal charging current. I would expect a pre-charge current of let's say 100mA or 200mA or so. Then, after some seconds, the charging current can go high to 2A or 3A or maybe 4A. But 9A sounds to me like a dead-short anywhere.
But it depends on the current demand of the product. What says the spec label on the bottom of the case about the required current and voltage?

[hobostove]

Okay, ordered another battery to rule that out.

The battery is at 11V right now. When I add AC power, the battery connector goes up to 19V briefly, then settles down at 11.5V, but it's not taking current. Taking off AC power, and it goes back down to 11V. I replaced the BQ chip.

I'm thinking one of the mosfets?

Datasheet: https://www.badcaps.net/forum/showthread.php?t=74069

[hobostove]

I found the low side mosfet PQ706 was shorted. I replaced it with one that tested good, but that one went short immediately. I tried another, and same thing, shorted. There's no short on the board. What could be killing these mosfets?

[mon2]

Which mosfet part number is being used for the replacement?

[hobostove]

I used AON7380. I ended up finding the first DC-in mosfets were short. Once I replaced those the low charging mosfet survived. It's charging now.

[mon2]

Excellent!