Lenovo no Bat+

[ziko07]

Hi, I was read about BQ chips but laptops is not mine primary job so can someone help?
I have no V9B+. And first mosfet not open and no any voltage on gate. Not shorted mosfets
Lenovo laptop, sch on image is from same laptop model

[mon2]

Remove all power. Meter in resistance mode.

Measure the resistance across the 2 x DCin mosfets.

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.

Do review the sticky above by piernov on charger circuits. Often, the 2nd DC in mosfet gets shorted and raises the issues you are observing.

If in a rush - replace the 2nd DCin mosfet -> test again. If still not working, replace also the 1st DCin mosfet.

Before proceeding, do check the resistance to ground of the main power rail. We need to be sure there is no short on this rail which would have caused the DCin mosfet(s) to get nuked. From experience, the DCin mosfets are damaged by in rush currents.

[ziko07]

Strange, all measurent are in MegaOhms, also I bring 0v8 on main rail not draw any current, will take second wolrking board to take some measurment

[ziko07]

I can't edit above post, just to tell I noticed when bring 19v to laptop , it draws very short (second) 24mA then goes to zero

[ziko07]

Update, when bring 19v to main rail laptop starts, I replaced first mosfet,not work still, second is 3x3 very small, can't find but can be BQ ic problem? Tnx

[mon2]

Is the posted schematic accurate for your board? This schematic shows both dcin mosfets to be the same size.

What are the topside markings on the mosfets that are on your actual board?

[ziko07]

Yes ,board view is accurate, I tried other mosfet deferent size but put wires, and still not works, both DCIN changed,with wire from plus input I connected to big resistor on main relay and laptop works ok, with no battery charging of course.
They had already same model and same fix and works to them...so will give as it is

Thank You for your help, always only you trying to help me
Regards

[mon2]

Glad to help where I can.

If you still have the unit, measure the full resistance path for the battery charge circuit. Be sure this full path measures to the values on the schematic.

Perhaps battery is old? Test with another known good battery. Either way, glad you made some progress.