Lenovo Ideapad Gaming 3 15ACH6 doesn't charge

[AleX.dans.les.nuages]

Hello from France

My daughter spill some water on her laptop... Lenovo Ideapad Gaming 3 15ACH6, and she doesn't seen anything wrong after just remove the water with towel.

Then, later the laptop won't start anymore.

I've made a basic troubleshoot with my own laptop (same series)

So, the computer battery is totaly out. With my battery, the computer works !

But, with PSU connected, the latptop detect the power.. the harware led white is on, the amber one too and on the screen there is a 'batt charging' message.

But there is absolutly no charge to the battery. (And the laptop doesn't goes to auto off, and kill the battery)


So, I've found the wiring on this message (thanks Lisa Su) and here (thanks to AL._.EX )

I've made some basic checks, and then, found the following :



The +19V_VIN is OK (20.1 volts)
On the point 'A' (PD303 cathodes), with no PSU, the batt voltage is present, and with PSU, the 20 volts is present.
On the point 'B', there is always the batt voltage.

And then for all the following, same thing :


ACDRV-1 (PQ303/PQ310 gate), 0V with batt, and 2.8V with PSU connected
ACDRV-2 (PQ301/PQ309 gate), 0V with batt, and 2.8V with PSU connected
CMSRC-1 (between source and drain of the mosfets), 0V with batt, and 2.8V with PSU connected

I'm not able to do the check on the pads 3(CMSRC) or 4(ACDRV) of the BQ24800 (datasheet https://www.ti.com/lit/ds/symlink/bq24800.pdf) and I can't locate the resistors.

But so, I think the BQ24800 is OK



Could you confirm PQ307 is a 'gate' between ACDRV and CMSRC command ?


Do you think that the problem root cause can be the mosfet PQ301/PQ303/PQ309/PQ310 ? Or can I check something else... ?

[mon2]

Hello and welcome. Yes, PQ301 / PQ303 are suspects. A must read is the sticky article on charger circuits above by piernov. He is also in France and we are hoping for his onsite (international) service but so far no go.

Remove all power. Meter in resistance mode. Measure each of the referenced DCin mosfets using resistance mode of testing.

Measure:

source (1-2-3) & drain (5-6-7-8)
source (1-2-3) & gate (4)
gate (4) & drain (5-6-7-8)

Each measurement should be hundreds of k ohms or higher else the mosfet may be defective and leaking. Review PQ303 and then PQ301. Since they both are driven by the common gate signal, it is possible that one defective mosfet can make both look bad. Often, the 2nd DCin mosfet is the defective one but suggest to test both.

Do you also have PQ309 / PQ310 onboard? To me it appears that either one pair of mosfets OR the other pair are being stuffed on this logic board.

[AleX.dans.les.nuages]

Yep, on this MB, there is 2 couples of mosfet





PQ301 and PQ309 : AON6426 (30V / 65A)
PQ303 and PQ310 : EMB12N03H (30V / 25A)





I've already seen (quickly) the sticked subject, but the chapter '2.2 battery not charging' is not really applicable... BTW, in the previous chapter, 2.1.3 something is really near my own case..

And so, I think you give me the good next step !!

Without battery and with no power supply, (with a very cheap multimeter) I get :

for PQ303/310 (+19V_VIN side)
gate (4) to source (1-2-3) : 6 ohms (same thing with reversed polarity)

drain (5-6-7-8) to source (1-2-3) : around 120 Kohms
source (1-2-3) to drain (5-6-7-8) : around 60 Kohms

drain (5-6-7-8) to gate (4) : around 120 Kohms
gate (4) to drain (5-6-7-8) : around 60 Kohms





for PQ301/309 (P3 or 'VBAT' side)
gate (4) to source (1-2-3) : 1 ohms (same thing with reversed polarity)

drain (5-6-7-8) to source (1-2-3) : above 1.5 Megohms
source (1-2-3) to drain( 5-6-7-8) : around 60 Kohms

drain( 5-6-7-8) to gate(4) : above 1.5 Megohms
gate(4) to drain( 5-6-7-8) : around 60 Kohms


Just one word from you, and I'll order it ! (probably 10 of each..)

[mon2]

Good. The gate / source measurements are much too low to be a good thing for both pairs. The best solution is to consider to repace each of these 4 mosfets, they should be inexpensive on Aliexpress. Just select a good vendor with a high rating. If you are in a rush, confident that we can find something suitable from Mouser / Digikey with higher costs but much faster delivery. If you select the 'rush' options from Aliexpress, I know that we are receiving goods in ~2 weeks here in Canada so suspecting that your delivery will be much faster.

Even the gate/drain measurements @ 60k ohms are too low for a good mosfet but these measurements may not be accurate due to the very shorted gate / source values.

You could even order a spare charger IC but that may be ok since the unit is working with the battery. Aliexpress has it all. Just be sure to order the exact part as noted in the schematics.

[mcplslg123]

Its best to remove the concerned mosfets from PCB and then check them out of circuit. The low readings may be from PCB .

[AleX.dans.les.nuages]

Parts ordered.. At ACoLab (local FabLab), there is an hot air station to replace it. (And to check mosfet out of the PCB mcplslg123 )