[SOLVED] Laptop Fine on AC, Battery Inserted Crashes It

[Appletax]

Edit: appears to be a bad AC adapter.

Got a Dell M731R laptop that works fine when plugged in and without the battery, but crashes with the battery inserted. Battery is OEM and listed in BIOS as healthy.

1) Customer stated that the battery would not charge and wanted me to replace the DJ jack as they believed that it was faulty, and they had the part in-hand.

2) Replaced the DC jack (plug-in, no soldering required).

3) Booted up & crashed after a few seconds - whether loading Windows 10 or just idling in the BIOS.

4) Removed the battery & crashing stopped.

5) Ran Prime95 with max power consumption on AC power with battery removed and it did not crash.

6) Turned off Prime95, inserted battery and it crashed.

7) Powered off laptop, held power button for 30+ seconds, turned back on, inserted battery - crashed.

8) Let the battery charge overnight. Now it seems to work fine. Prime95 does not cause crashing.


Other thoughts:

1) People have suggested calibrating the battery, but that's not possible when it causes the system to crash.

2) One person found their motherboard had a short and had to replace it.

3) Other suggestion is to use a multimeter to test the battery's voltage levels. Or try replacing it.

 

[Markverhyden]

Not sure about others but if a laptop is powered up on just AC I do not just pop in the battery. I always shut down them down before putting in a battery.

 

[Appletax]

Not sure about others but if a laptop is powered up on just AC I do not just pop in the battery. I always shut down them down before putting in a battery.

Occured even when putting battery in with laptop shutdown.

Wanted to see what would happen if I inserted it when the computer was up and running fine.

 

[coffee]

Could be a short somewhere in the battery charge circuit that is taking more power than it should. When it does this the power rail will drop down in voltage and crash the system - something like that.

My theory is: Since the battery is now fully charged it will not do this. This is because the battery says "hey, Im fully charged" to the laptop and so the charging to the battery is scaled back or turned off until needed. When it finally drops down to a certain charge level you might experience this problem again. My theory anyways.

 

[Appletax]

Could be a short somewhere in the battery charge circuit that is taking more power than it should. When it does this the power rail will drop down in voltage and crash the system - something like that.

My theory is: Since the battery is now fully charged it will not do this. This is because the battery says "hey, Im fully charged" to the laptop and so the charging to the battery is scaled back or turned off until needed. When it finally drops down to a certain charge level you might experience this problem again. My theory anyways.

Right now I am running Prime95 on just the battery and it has not crashed.

Sounds like the only fix would be to replace the entire motherboard?

The battery charge circuit is integrated on the motherboard?

 

[backwoodsman]

New Edit: seems to be fine now. What was the issue?

Maybe a dying AC adapter that can still put out enough current to run the computer, or charge the battery, but not both at the same time?

 

[Appletax]

Maybe a dying AC adapter that can put out enough current to run the computer, or charge the battery, but not both at the same time?

The issue was occuring when the battery was inserted and AC adapter unplugged.

I could test the AC adapter (OEM) with a multimeter.

 

[backwoodsman]

I could test the AC adapter (OEM) with a multimeter.

May not give you a useful reading unless you can test voltage under load. Do you have another AC adapter you can try?

 

[Appletax]

May not give you a useful reading unless you can test voltage under load. Do you have another AC adapter you can try?

Duracell universal AC adapter.

Right now it is working just fine. Gonna drain the battery and see what happens. Will try my adapter.

 

[coffee]

Right now I am running Prime95 on just the battery and it has not crashed.

Sounds like the only fix would be to replace the entire motherboard?

The battery charge circuit is integrated on the motherboard?

Yes, The charge circuit is in the motherboard. There is another circuit in the battery that updates the laptop on its current state - whether is low / fully charged / charging / not charging. They talk to each other.

There is probably a short in the charge circuit that is drawing too much power. So, It makes the laptop unstable. Then the KBC is shutting down the laptop - or something like that.

 

[backwoodsman]

Duracell universal AC adapter.

I'm not familiar with that model, but if it's like most Dells, it'll only charge the battery with a genuine Dell AC adapter.

 

[coffee]

If you were to look at the schematic for that laptop you would see that there is a power IC for the battery charge circuit and some other circuits. I would start there - perhaps its failing with an internal short.

It will probably be similar to this:

https://www.ebay.com/itm/1x-NEW-Pow...h=item35be0ab6cd:g:Z-gAAOxyFd1SK3b0:rk:1:pf:0

From this chip you can test the circuit right back to the battery if you want to actually go that far in troubleshooting. In fact, It will probably feel hot to the touch with the power adaptor and battery plugged in - maybe....

 

[Appletax]

I ran the battery to 0%. Started it up with no issue even @ 0%. Plugged in the AC adapter and now it does not say that the battery is charging. It is telling me that I am running on battery.

 

[Porthos]

You need a genuine Dell Adapter to charge.

 

[Markverhyden]

Many of those machines using chipped chargers will charge with a power compatible generic when the computer is turned off. At least that worked on a couple of Sony's and Dell's several years ago.

 

[coffee]

Check the voltage on the middle pin of the charger. If there is no voltage then its not going to charge no matter what.

 

[Appletax]

Check the voltage on the middle pin of the charger. If there is no voltage then its not going to charge no matter what.

The readout was nearly 0 when touching the pin with the red probe of the multimeter. Touching the inside wall resulted in the correct voltage.

Left the laptop to charge overnight and it did not.

Have my Duracell universal adapter plugged in and it's allowing it to run but the battery is not charging.

Will tell the customer they need a new AC adapter (Dell/OEM only).

 

[coffee]

Glad to hear it was only the charger

HP and Dells have the Adapter Sense on the middle pin and a very low current. I think the voltage should be around 14v for the middle pin on the Dells. HP's I dont know.

 

[Appletax]

Glad to hear it was only the charger

HP and Dells have the Adapter Sense on the middle pin and a very low current. I think the voltage should be around 14v for the middle pin on the Dells. HP's I dont know.

If the middle pin is low current, then getting a low voltage reading is normal and thus that test is not useful for this AC adapter?

Hopefully it's as simple as replacing the AC adapter.

 

[coffee]

If the middle pin is low current, then getting a low voltage reading is normal and thus that test is not useful for this AC adapter?

Hopefully it's as simple as replacing the AC adapter.

Im thinking my 14v is wrong then. I know its a data pin so it might be like 1.5 to up to 5v.