Need help for battery issue (MAX8731A) on Dell Inspiron 1525

[SRO2]

Hello !

I have a problem with a Dell Inspiron 1525 computer motherboard. The computer refuses to charge the battery, when I am under Windows it says "Plugged in, not charging" and there is no charging indicator light on the front of the computer.
However, the computer works without the charger when the battery is already charged, and it also works when there is only the adapter connected.

I charged the battery with another computer and it charges well, so the battery works.

I have already made some measurements using the motherboard schematic (thanks JaroTech), and I got these measurements when the adapter and battery are connected to the motherboard:

(See MAX8731A-AdapterBatteryConnected.png)

Looking at the MAX8731A documentation I think the measured values are correct, but I don't really understand how the MOSFETs that allow the battery charge are controlled...

I saw that the signal wire AC_IN# that goes to WPC8763LDG switches well from the high logic state to the low logic state when I connect the charger so I think the "computer" detects well that the battery must charge.

Maybe the problem comes from the battery charge control MOSFETs but I would like to be sure that the values measured on the MAX8731A are good before controlling the MOSFETs (especially since I don't really understand which ones must be "passing" to charge the battery...)

Thank you in advance for your help!


See below motherboard schematic, MAX8731A datasheet and measurements on the MAX8731A :

[Techtiger]

Re: Need help for battery issue (MAX8731A) on Dell Inspiron 1525

Test Voltage L14 both sides
Voltage in battery connector

[Jesse James]

Re: Need help for battery issue (MAX8731A) on Dell Inspiron 1525

I ran into this many times on Dell 1525 and 1545 and it always turned out to be the charging port. Sometimes it would work with another adapter. Hope this helps

[SRO2]

Re: Need help for battery issue (MAX8731A) on Dell Inspiron 1525

I'll do the measurements tonight and tell you. I have already tried different adapters for this computer, without success.

I have tried 3 and the one I am currently using for the tests has a blue light ring on the male plug (if this can help).

Thank you for this feedback anyway!

[SRO2]

Re: Need help for battery issue (MAX8731A) on Dell Inspiron 1525

I measured the voltage on both sides of L14 and there is 11.14V
I also measured the voltages on the battery connector.
The voltage of the CLK_SMB pin varies slightly between about 3V-3.20V, but since it is a clock...


On the other hand, the battery connected to the motherboard has still some autonomy so I don't know if this could be a problem for the measurements.

[Techtiger]

Re: Need help for battery issue (MAX8731A) on Dell Inspiron 1525

BATT_PRS# Signe is missing 3D3V AUX S5 test the R21 470k

[SRO2]

Re: Need help for battery issue (MAX8731A) on Dell Inspiron 1525

R21=414khm
R22=100ohm

On the 3D3V_AUX_S5 signal I have 3.315V.

[Techtiger]

Re: Need help for battery issue (MAX8731A) on Dell Inspiron 1525

R21=414khm
R22=100ohm

On the 3D3V_AUX_S5 signal I have 3.315V.

so pin 5 of battery connector 3.3V ?

[khaahk]

Re: Need help for battery issue (MAX8731A) on Dell Inspiron 1525

Pin 5 is probably pulled low by battery to indicate to the ec that it is inserted. It has # prefix, meaning low value is true.
From max8731 measurements it is hard to say - the gate driving signals should be looked with oscilloscope. Measure mosfets U8, U7, U5 for low resistance onboard and if unclear result then offboard.

[mcplslg123]

Re: Need help for battery issue (MAX8731A) on Dell Inspiron 1525

I think pin 23 & 24 measurement are wrong indicating low side and high side gates of fets are not opening.

[Duranitron]

Re: Need help for battery issue (MAX8731A) on Dell Inspiron 1525

Hello !

I have a problem with a Dell Inspiron 1525 computer motherboard. The computer refuses to charge the battery, when I am under Windows it says "Plugged in, not charging" and there is no charging indicator light on the front of the computer.
However, the computer works without the charger when the battery is already charged, and it also works when there is only the adapter connected.

I charged the battery with another computer and it charges well, so the battery works.

I have already made some measurements using the motherboard schematic (thanks JaroTech), and I got these measurements when the adapter and battery are connected to the motherboard:

(See MAX8731A-AdapterBatteryConnected.png)

Looking at the MAX8731A documentation I think the measured values are correct, but I don't really understand how the MOSFETs that allow the battery charge are controlled...

I saw that the signal wire AC_IN# that goes to WPC8763LDG switches well from the high logic state to the low logic state when I connect the charger so I think the "computer" detects well that the battery must charge.

Maybe the problem comes from the battery charge control MOSFETs but I would like to be sure that the values measured on the MAX8731A are good before controlling the MOSFETs (especially since I don't really understand which ones must be "passing" to charge the battery...)

Thank you in advance for your help!


See below motherboard schematic, MAX8731A datasheet and measurements on the MAX8731A :

just a suggestion. focus on battery charging ic and around it. probably a shorted mosfet or blown coil or fuse. check signal pin of mosfet or replace the mosfet to check it. hope this helps.. try again till you fixed it.

[SRO2]

Re: Need help for battery issue (MAX8731A) on Dell Inspiron 1525

Pin 5 is probably pulled low by battery to indicate to the ec that it is inserted. It has # prefix, meaning low value is true.
From max8731 measurements it is hard to say - the gate driving signals should be looked with oscilloscope. Measure mosfets U8, U7, U5 for low resistance onboard and if unclear result then offboard.

You advise me to visualize which signals with the oscilloscope?
DHI (24); DLO (20) and the gate of U5?

Thank you all for your help

[SRO2]

Re: Need help for battery issue (MAX8731A) on Dell Inspiron 1525

I visualized the following voltages with the oscilloscope, and they are all direct voltages, without parasites, very clean...

U5 Gate=19.6V Source=19.6V Drain=11.4V

U8 Gate=11.2 Source=11.6V Drain=19.6V

U7 Gate=0V Source=0V Drain=11.8V

Everything looks okay, I really don't see what the problem is.
I can try to order another MAX8731A but I don't believe in it too much...

EDIT :

I just realized that the person who gave me the computer had disabled in the BIOS the verification of the adapter... when I reactivated it I got a nice error message at startup..:

"The AC power adapter wattage and type cannot be determined.
The battery may not charge.
The system will adjust the performance to match the power available.
Please connect a Dell 65W AC adapter or greater for best system performance"

I had tried with several adapters (2 Dell and one generic) and I think none of the adapters I tried are compatible. I'll get a 65W adapter from a Dell 1545 I'll see if it works... I'll keep you informed!

I looked for something far too complicated for lack of information I think... as Jesse James said if it turns out it's just a charger problem:/

[khaahk]

Re: Need help for battery issue (MAX8731A) on Dell Inspiron 1525

If the adapter is ok, then you might have a problem with adapter id circuit, PG38 on schematic. When charging the mosfet driving signals on gate should be impulses of about 25V on high side mosfet and 5V on low side mosfet.

[mcplslg123]

Re: Need help for battery issue (MAX8731A) on Dell Inspiron 1525

if you are getting adapter warning msg on startup then very likely you have problem in PS ID line. Look for 33.4 ohm resistor. thats the culprit in most of dell's

[SRO2]

Re: Need help for battery issue (MAX8731A) on Dell Inspiron 1525

I get the adapter back tonight so I'll tell you, however I didn't find a "PG38" circuit on the documentation.

And for the 33.4ohm resistance what is its designation Rxx ?

[SRO2]

Re: Need help for battery issue (MAX8731A) on Dell Inspiron 1525

And for the 33.4ohm resistance what is its designation Rxx ?

I think I found the 33ohm resistor, it seems to be R220 (Page 38/47).

[SRO2]

Re: Need help for battery issue (MAX8731A) on Dell Inspiron 1525

I've come to give you some news because I've finally solved my problem!
The failure did not come from the adapter or the motherboard, it came from the "powerjack board".
I didn't know that the Dell adapters were communicating with the motherboard via a 1-wire bus (the connectivity in the center of the powerjack), when I saw this I tried to visualize if data was transmitted between the adapter and the motherboard with my oscilloscope but nothing (except noise from the mains voltage...).
Then I checked if there was a connection between the central plot of the powerjack and the connector that goes to the motherboard, and I saw that there was no continuity. So I followed the track from the connector to the powerjack and found a place where it was cut off.

So I restored the contact between the central plot of the powerjack and the corresponding pin on the connector that goes to the motherboard. After briefly reassembling the PC I plugged in the adapter and there was a miracle: the charge indicator lights up, no more error messages when starting, and the battery is charged =)

Thank you all for your advice and help, thanks to that the problem is solved!

Some interesting links:
https://hackaday.com/2014/03/03/hack...dentification/
http://neighborhoodsupport.net/?entr...11005-06383845

[Techtiger]

Re: Need help for battery issue (MAX8731A) on Dell Inspiron 1525

I've come to give you some news because I've finally solved my problem!
The failure did not come from the adapter or the motherboard, it came from the "powerjack board".
I didn't know that the Dell adapters were communicating with the motherboard via a 1-wire bus (the connectivity in the center of the powerjack), when I saw this I tried to visualize if data was transmitted between the adapter and the motherboard with my oscilloscope but nothing (except noise from the mains voltage...).
Then I checked if there was a connection between the central plot of the powerjack and the connector that goes to the motherboard, and I saw that there was no continuity. So I followed the track from the connector to the powerjack and found a place where it was cut off.

So I restored the contact between the central plot of the powerjack and the corresponding pin on the connector that goes to the motherboard. After briefly reassembling the PC I plugged in the adapter and there was a miracle: the charge indicator lights up, no more error messages when starting, and the battery is charged =)

Thank you all for your advice and help, thanks to that the problem is solved!

Some interesting links:
https://hackaday.com/2014/03/03/hack...dentification/
http://neighborhoodsupport.net/?entr...11005-06383845

Thanks SRO2