Lenovo ThinkPad E14 Gen 4 not charging

[chris1379]

We have a ThinkPad E14 Gen 4 that operates from the battery only but will not charge. 20V is present near the USB-C port. I'm new to laptop board troubleshooting. I can't figure out where the charge voltage comes from. Which MOSFETS do I check first? The board is NM-E211.

[mon2]

Schematics & BV files are posted here:

LENOVO ThinkPad E14 E15 GEN 4 INTEL NM-E211 - Badcaps

If you have 20v then the power delivery controller on the logic board has properly negotiated with the power delivery adapter to dial up this 20v contract. Monitor the power path from this power adapter to the battery charger @ PU4000.

Review the voltage to ground (very carefully) on the dual mosfets @ PQ4000. What is the voltage to ground on pin # 7 of PQ4000? You should be able to measure the same voltage of interest at the inductor @ PL4001.

Next, review the voltage to ground @ pin 2-3-4-10 (any will do) of PQ4001. Do this without the battery connected so we can monitor the power path from the adapter to the main power rail on the logic board.

Post each measurement.

Most likely, one of the DCin mosfets is shorted and not allowing for the battery charge or even the logic board power.

[chris1379]

Something strange is going on. I was measuring 0V (no battery) at PL4001 and fluctuating voltage at PL4000 and PR4000, 3-6V with no battery. LB4708 had 20V. I'm not sure what is between them. I connected the battery and it started charging. It's almost 12.4V now. I have disconnected and reconnected two batteries and two chargers multiple times without it charging. It seems to be normal for now and I can disconnect and reconnect the charger. I'm going to look closer tomorrow for cold solder joints. Thank you so much and I will keep you posted.

[chris1379]

I am waiting on a fan as I damaged the wires but it is charging consistently now. I am a little worried because I did not replace any parts to fix it.

[chris1379]

Came back for same problem. Replaced Battery and worked OK for a few days. Same Problem again.

[isr_149]

Thank you