Alienware 17 R4 Charging issue

[bastardman]

Hi there.
I have one of these models which has an issue charging the battery. Usually it reports in Windows that it is plugged in and charging but the charge % doesn't increase. It will, after a while, then report plugged in not charging. Leaving the unit powered off but still plugged in makes no difference, the LED indicates it is charging. The AC Adapter is correctly identified as a 240W unit, battery health reports fine and this was also the case when running onboard diagnostics.

I have tried a replacement battery and used a second identical AC Adapter. The unit otherwise has no other issues and runs fine on the adapter, however, the battery level had been slowly dropping. It is now 6% because I forgot to turn on the adapter while I was in a hotel damnit. I have also updated to the latest BIOS and have tried several times the disconnect battery-hold power button method as well as uninstalling the battery driver.

I've measured voltages ok at the DC-In socket on the mainboard but there doesn't appear to be any voltage out at the battery connector. Online sellers are charging quite a lot for a replacement board so I would like to see if there's anything I can do to fix the fault.

Motherboard details; AW 17 R4, Compal LA-D751P with i7-7700HQ + GTX1070 w/ 8GB

[mcplslg123]

Re: Alienware 17 R4 Charging issue

Do you mean that the new battery when connected and turned on, with adapter plugged in, shows plugged in charging but percent actually drops?? If so likely some mosfet leaky in charging circuit

[bastardman]

Re: Alienware 17 R4 Charging issue

Hi, yes that description is correct. It is very slow, maybe 1% drop over a couple of days but it does go down. Thanks for the reply, something for me to check.

[mcplslg123]

Re: Alienware 17 R4 Charging issue

1% drop over a couple of days is not abnormal.

[MJ-meo-dmt]

Re: Alienware 17 R4 Charging issue

In usual states there should be something on the + pin for the battery terminal something like 2.6V or less. And 2 of those pins should give 3.3V which is the EC comms. But I found that sometimes these have a sense pin and if it doesn't sense anything the connector terminal is "OFF" which == no voltages....

Anyways with regards to the Plugged in Charging and not actually charging check the following:

Check the sense resistors on the charge rail resistor. Make sure they feed back into the charging chip.

CSOP & CSON from sense resistor, and BQ side they are usually either the same or SRP, SRN.

The resistors are usually low enough to let a diode test from a multimeter go through like when you do continuity test. So that way you would know if there's an open in the trace. But check the resistance in anycase. They aren't that specifc to makes.

Check the SCL/SDA connections to the EC and back to the Charger Chip as-well. But having a LED kinda tells me that communication is fine and its most likely the sense circuit.

Obviously assuming you already checked the Coil and mosfets... But since it says plugged in charging but not charging I don't think its either of those. Unless one of the mosfets is acting up...

Attached is a cutout from another ALienware to give you an idea of what values to work with.

[bastardman]

Re: Alienware 17 R4 Charging issue

Thank you for that.
I was also running this past an ex-boss who also had PCB experience. I pulled out the board in order to give him a photo of the components on the other side of the DC-IN & BATT connectors and noticed a soot mark near the rear of the unit. Sure enough on the board there is a blown SMD cap. It is above where the CPU is on the other side and lines up with what I presume to be the CPU voltage regulator section. Could this be in any way related? As I've said the unit otherwise functions ok up to and including a gaming load such as Fallout 4.

I've attached a photo indicating the cap in question.

[bastardman]

Re: Alienware 17 R4 Charging issue

Hmm, I haven't had much luck so far identifying similar components on this board to the ones in that other model as shown in the schematic. The closest thing I can see being the charging controller might be PU201, it's damn tiny though. Also not sure I'm seeing the sense resistor.
Attached some additional photos showing what I presume to be the charging area of the main board between the DC-IN and BATT connectors.

Regarding that cap I'll have to check if meters I have at home can measure capacitors so I can check the values of neighbouring ones. Unless anyone might have an idea.

Edit:
Looks like PR712 could be the sense resistor, I've traced this through the nearby three caps to the two caps right above PL201 to the adjacent resistors then to PU201. Didn't note anything unusual there.

[MJ-meo-dmt]

Re: Alienware 17 R4 Charging issue

That cap that is blown up - replace that... I don't think that would cause the no charging effect. But since that blew it could have created a spike...

Check the mosfets on the charging circuit like mcplslg123 mentioned.

You should trace backwards from the battery terminal to see which is the battery side sense resistor. PU201 almost looks like the powercontroller for the RAM. But anyways.

[mcplslg123]

Re: Alienware 17 R4 Charging issue

PU201 seems like 4B= ic which is RT8207L-memory controller as mj-meo-dmt has suggested.