la-d101p battery not charging

[ahmarzo]

la-d101p laptop having bq24780 charging ic the problem is no voltage on gate of input mosfet.charging ic has vcc 19v ,acdet 2.7 v,acok 0v, acdrv 0v. schematic is not available please how to solve this problem

[mon2]

Re: la-d101p battery not charging

Hi.

Remove the ~4k series resistor on the ACDRV pin of the charger. Then measure again on the ACDRV pin. Do not lose this resistor.

Do you now have ~25v on ACDRV ?

Measure also the voltage of REGN pin.

Often the fault is in the 2nd DCin mosfet that gets damaged but start with these tests.

[ahmarzo]

Re: la-d101p battery not charging

hi thanks for reply
after removing 4k resistor acdrv is same 0v and regn on pin no 24 is 6v. after removing second mosfet acdrv starts.i have changed it but problem remains same.

[mon2]

Re: la-d101p battery not charging

Remove all power. Meter in resistance mode. Measure the resistance to ground of each coil on the board. This is to confirm there is no shorted part on a power rail. Check for low resistance readings.

Q: does the laptop work but does not charge?

If it does not power, continue to measure.

[ahmarzo]

Re: la-d101p battery not charging

the laptop works fine when i pass the input voltage on first mosfet and yes it does not charge

[mon2]

Re: la-d101p battery not charging

Can you post a pic of this area of the logic board?

Sometimes, the designs will feature a discharge mosfet (SOT-23 / SC-70 package) that causes issues. Often, it is placed between the first and 2nd DCin mosfet.

If present, remove it and test again.

Also, confirm the details of the DCin mosfets -> remove all power -> meter in resistance mode.

Measure the resistance across the mosfet pins:

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 of each DCin mosfet. If the reading is low, the mosfet is defective and must be replaced.

[mcplslg123]

Re: la-d101p battery not charging

Problem is not ACDRV but ACOK which is zero.

[MrFunkyhead]

Re: la-d101p battery not charging

how about injecting 10v on the source of the second mosfet and measure the voltage on the battery +.if you get 10v then its a bad mosfet.

[mcplslg123]

Re: la-d101p battery not charging

how about injecting 10v on the source of the second mosfet and measure the voltage on the battery +.if you get 10v then its a bad mosfet.

Clear No NO. Why play with voltage injection without diagnosing the fault and that too with 10V?? I see another post from you advising to inject 19V. these are almost sure way to kill a mb instead of getting them fixed.

Mb doesnt take much time to get repaired but it may take much time in diagnosing it and thats where patience is a pre-requiste.

[MrFunkyhead]

Re: la-d101p battery not charging

Ok.