LENOVO YOGA 7 14ITLS 15 BATTERY REPLACEMENT PROBLEM

[NConstantinou]

Dear all,

i have the above laptop which had a problem with battery. i replaced it with a compatible one..
the laptop DOES NOT POWER ON..
with it old battery it does power on.
i left the new battery disconnected and i powered on the laptop and i reconnected battery while laptop was on. it shows that the battery is charging.
when i shutdown the laptop does not power on.

does anyone have any solution!
when is not power on the usb c voltage tester shows 5v 1.3A

when i disconnect battery and power on and then connect battery the tester usb shows 19v as input


thanks

[mon2]

Remove all power. Meter in resistance mode.

Measure the resistance across the mosfet pins to test if they are leaking.

Review the mosfet @ PQ304:

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.

[NConstantinou]

SOURCE TO DRAIN 21M AND DICREASING
SOURCE TO GATE 208K
GATE TO DRAIN 20M

MULTIMETER IS NOT STABLE IN ALL READINGS IT FLATUATES

[mon2]

These are low measurements for source/drain and source/gate.

Flux and remove this part. Allow it to cool. Then measure this part again to see if the readings are still this low. Suggest to replace this part and test again.

[NConstantinou]

ok i will do that but what should be the readings

[mon2]

Each measurement should be hundreds of k ohms or higher on a good part.

[SMDFlea]

Tried another replacement battery ?

[NConstantinou]

CAN I SUBSTITUTE AON7380 WITH AON7516!
TO ORDER AON 7380 WILL TAKE AT LEAST 2 WEEKS TO ARRIVE.

THANKS

[mon2]

CAN I SUBSTITUTE AON7380 WITH AON7516!

Yes.

[NConstantinou]

still the same problem
voltage is flutuating.
could that be the charger ic!

[mon2]

Remove all power. Test each mosfet that is driven by this charger IC. You are hunting for other defective parts in this region.

See the sticky above by piernov on charger circuits.

[NConstantinou]

is it possible the charger ic maybe defective!
After studying BQ25710 i connected only battery on motherboard and i notice that the problem is on EC_SMB_CK1 and EC_EMB_DA1.
those 2 pins are connected to RPE3 pins 1 & 1 3v is fluctuating BUT pins 3&4 i get stable 3.3v.
Those EC_SMB_CK1 & EC_SMB_DA1 are the outputs of BQ25710 charger ic

[mon2]

The BQ charger IC is the slave node on the I2C / SMBUS network. The I2C / SMBUS master is the EC and the EC is the one that drives the clock line. One side of the required pull-up resistors must be at 3v3 or similar (varies with the logic levels needed by the slave nodes) but the other side or the active side will be toggling high and low so your meter is observing as fluctuations.

If of concern, test if these lines are being shorted. Remove all power. Meter in resistance mode. Measure the resistance to ground of the CK1 and DA1 lines. If the resistance is low then yes, someone is defective and it could be the ESD TVS diodes. We have this event on a few cases and took longer than it should have to locate the tiny buggers that demand nice tweezers to pluck off the board. Made the macbook look dead to the world and multiple local shops gave up on it. The same defective TVS diode was shunting this line and causing the main buck / boost regulator from creating the required PPBUS_G3H rail. Your case may be similar.

[NConstantinou]

Thanks MON2

it seems that my multimeter was defective and i notice it too late after spending a lot of time to realize it.
getting a new multimeter the resistance is as follow

PQ 305 D to S 2.4M, S to G 1.5M, D to G 8M
PQ 303 D to S 1.7M, S to G 0.2M, D to G 1.9M
PQ 304 D to S 9M, S to G 2M, D to G 7M

when i was testing PQ305 D to S the multimeter reading was increasing more rapidly than the other readings if that is telling you something.
PQ305 is 5W3502 and is before PR302.

the EC_SMS da&cl are not short. their resistance is about 30k

[mon2]

PQ 303 D to S 1.7M, S to G 0.2M, D to G 1.9M

This mosfet is a suspect. The S/G measurement is a bit on the low side. Consider to flux and remove this part and confirm if the measurements remain the same. This part may be defective.

[NConstantinou]

I REPLACED AON7408L WITH 7408 BUT STILL GET 0.2M RESISTANCE.
GROUND TO GATE IS THE SAME RESISTANCE

[NConstantinou]

According to the diagram there is a capacitor PC331 100p_50v that is connected to the gate of PQ303.
On board there is no such a capacitor. i found one and i solder it but resistance still low onPQ303 S to G at 0.2M with the capacitor install

[mcplslg123]

Have you tried another battery?
Too me nothing seems wrong here and perhaps the unit may be damaged by un-necessary steps at this stage.
The compatible battery is simply not compatible with this unit.
Post the original battery+new battery PICS

[NConstantinou]

No i do not have that type but this battery works on another Lenovo.
i am sending you pictures of original and compatible

[SMDFlea]

No i do not have that type but this battery works on another Lenovo.
i am sending you pictures of original and compatible

To save anyone else having to download,extract,rotate pictures and zoom in to see the part numbers i`ll post the pictures and part numbers

Both battery models: L19M4PDC