Lenovo Legion Y520, not charging.

[Crabolog]

Hi everyone, appreciate any advice on following:

A laptop Lenovo Legion y520 came to me, not charging, AC led dark.
I've changed two capacitors in the AC line which were shorted, and now it's working from AC and says that battery is charging, however battery % is not growing (been waiting a few hours).

I'm not sure why, could anyone please advice what can I check?
on JBATT1 connector:
EC_SMB_DA1 = 3.2v
EC_SMB_CK1 = 3.2v
BATT+ signal only appears when battery is connected, and it's 10.47v which I assume is just coming from battery. Shouldn't it be 12v when battery is charging? And if yes, what can I check to identify why it is missing? If I check this signal without battery connected it's 0.6v and resistance to the gnd is 347kOhm

[mon2]

Re: Lenovo Legion Y520, not charging.

Battery charge profile can vary with the designer. Do not expect a fixed value here to be the same as others. Which charger IC is onboard? Post the topside markings.

Perhaps the 'BQ' series from Texas Instruments?

[Crabolog]

Re: Lenovo Legion Y520, not charging.

Bq24780s

[mon2]

Re: Lenovo Legion Y520, not charging.

Attach the adapter and battery. Power up and carefully measure the voltage to ground of each pin on the charger IC.

Post the readings and the pin numbers.

[Crabolog]

Re: Lenovo Legion Y520, not charging.

PU201 PINS:

1 ACIN = 19.78v
2 ACP = 19.78v
3 CMSRC = 20.46v
4 ACDRV = 20.46v
5 ACOK = 3.2v
6 ACDET = 2.8v
7 IADP = 0.079
8 IDCHG = 0.008v
9 PMON = 0.096v
10 PROCHOT = 1.021v
11SDA = 3.27v
12 SCL = 3.27v
13 CMPIN = 0.193v
14 CMPOUT = 0.127v
15 BATT_TEMP = 0.3v
16 TB_STAT = 1.35v
17 BATSRC = 11.37v
18 BATDRV = 11.36v
19 SRN = 11.37v
20 SRP = 11.37v
21 ILIM = 1.358v
22 GND
23 LODRV = 0v
24 REGN = 6v
25 BTST = 11.12v
26 HIDRV = 11.37v
27 PHASE = 11.38v
28 VCC = 20.2v

[mon2]

Re: Lenovo Legion Y520, not charging.

ACDRV is low and is not boosting to the required ~25v to enable the DCin mosfets.

Locate the ~4k resistor on the ACDRV pin. Flux and carefully remove this part but do not lose it.

Then power up again.

Check the voltage of the ACDRV pin at the charger IC.

Is it now ~25v ?

Often the 2nd DCin mosfet gets damaged and causes such faults. Do review the above sticky by @Piernov on this topic.

[Crabolog]

Re: Lenovo Legion Y520, not charging.

Can confirm ACDRV is now 25.56, laptop appears to be charging. So I should dig closer to PQ201 & PQ202 mosfets?

[mon2]

Re: Lenovo Legion Y520, not charging.

If the ACDRV is boosted, the DCin mosfets should be enabled and charging the battery.

If the battery charging fails, update this thread. Do test with a known good battery.

[Crabolog]

Re: Lenovo Legion Y520, not charging.

I can confirm that battery is charging after I removed pr206 resistor from ACDRV line. But should I just leave it as it is? I assume something is still not good since I needed to remove this resistor?

[mon2]

Re: Lenovo Legion Y520, not charging.

If ACDRV has returned without PR206, this is a good sign for the charger IC.

However, without PR206, the gate voltage should not be enough on PQ201 & PQ202 to be enabled.

Confirm the voltage to ground of the gate pins being shared between PQ201 & PQ202 = pin # 4.

Being N-channel mosfets, the gate voltage must be higher than the voltage being passed between source / drain pins.

At this stage, suspect that you have a leaky mosfet @ PQ202.

Confirm this by removing all power -> meter in resistance mode.

Measure the resistance between the following pins on PQ202:

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


Post each measurement.

Often, the 2nd mosfet = PQ202 on your board, gets damaged and needs to be replaced.

In summary, you require ACDRV to be ~25v with PR206 installed. Given that ACDRV is lower once PR206 is installed implies you have a defective / leaky mosfet stopping this party.

[Crabolog]

Re: Lenovo Legion Y520, not charging.

Does 445 Ohm between source and gate means its shorted?

[mon2]

Re: Lenovo Legion Y520, not charging.

Yes!! Flux and remove this mosfet to check the same measurements when the mosfet is on your work table.

[Crabolog]

Re: Lenovo Legion Y520, not charging.

Issue resolved by replacing both PQ201 and PQ202. PQ201 was also damaged.
Big thanks for your help

[dune6170374]

Big big thanks mon2 ;-)
your explanations are just perfect