Asus X512F won't hold on battery charge

[mon2]

Re: Asus X512F won't hold on battery charge

Remove all power. Meter in resistance mode.

Suggest to review the mosfet resistance values to confirm if they are normal.

Check the resistance of:

source (1-2-3) & drain (5-6-7-8)
source (1-2-3) & gate (4)
gate (4) & drain (5-6-7-8)

Review the high side, low side and also the battery mosfet that are linked to the charger IC.

Post each measurement. For the battery mosfet (n-channel) to be turned ON, the BATDRV voltage should be ~6 volts higher than the BATSRC voltage.

When the power adapter is removed, the battery mosfet gate pin should be at BATSRC voltage + 6 volts. This is the BATDRV pin on the charger IC. Confirm it.

Given that REGN is not supplying the expected 6 volts, suspicion is on the charger IC being defective. The LDO should offer this voltage unless there is an excessive load but this will lead to the internal LDO heating up and shutting down.

Q: If you REMOVE the battery and use only the power adapter, does REGN supply the 6 volts ? You can try the LDO without the cap for a quick test but do not believe this cap is the show stopper.

[Kambi13]

Re: Asus X512F won't hold on battery charge

Right, maybe I'll try to source a new BQ chip, as it feels that this one is messed up.

[mon2]

Re: Asus X512F won't hold on battery charge

It is a good idea and they are cheap. Be sure to flux and be patient in the surgery to replace it. Low air pressure. Aliexpress will have these.

Do check the mosfets and it does not hurt to order spares. We often order a bunch of the mosfets that surround the charger IC to cover our bases. Be prepared (GI Joe).

[Kambi13]

Re: Asus X512F won't hold on battery charge

Indeed, can you provide a good vendor that you use in Alixepress. Last one I got from one vendor was crap. the ic legs were recessed and it was a pain to get it soldered, and in the end none of them worked fine.

[Kambi13]

Re: Asus X512F won't hold on battery charge

Update,
So got a brand new charger IC BQ24780s, change both the high side and low side mosfets, and also the battery one
Just cant get BATDRV to get 6V above BATSRC. I also changed both 2 10k resistors that Asus uses at BATSRC / SRN and SRP (this last one was ok)
The battery has 80% charge and it won't go above it, if I remove power the laptop turns off.
Puzzling stuff

[mon2]

Re: Asus X512F won't hold on battery charge

Attach power adapter and battery.

Carefully measure the voltage to ground of each pin on the charger IC.

Post your readings with their pin numbers.

[Kambi13]

Re: Asus X512F won't hold on battery charge

1 - ACN -> 19,37v
2 - ACP -> 19,37v
3 - CMSRC -> 18,91v
4 - ACDRV -> 24,29v
5 - ACOK -> 5,98v
6 - ACDET -> 2,642v
7 - IADP -> 10.1mv
8 - IDCHG -> 9,4mv
9 - PMON -> 6,0mv
10 - PROCHOT -> 0v
11 - SDA -> 3,24v
12 - SCL -> 3,24v
13 - CMPIN -> 252.8mv
14 - CMPOUT -> 6.3v
15 - BATPRESS -> 9,5mv
16 - TB_STAT -> 9,8mv
17 - BATSRC -> 8,31v
18 - BATDRV -> 8,31v
19 - SRN -> 8,31v
20 - SRP -> 8,31v
21 - ILIM -> 1,171v
22 - GND
23 - LODRV -> 0v
24 - REGN -> 6.04v
25 - BTST -> 14.55v
26 - HIDRV -> 8,56
27 - PHASE -> 8,31
28 - VCC -> 18,99v

[Sephir0th]

Re: Asus X512F won't hold on battery charge

For me everything looked and looks in specs and the variations might be simply caused by the multimeter. Well, you can proceed dig around, or force the twist with a known good battery. It is the first thing which should have been ruled out as even stated in piernov's charging circuit guide, pinned in this forum.

[Kambi13]

Re: Asus X512F won't hold on battery charge

True, the fact is that the battery was working before, but I'm guessing that something is faulty in the battery itself. Maybe it's locked... I'll see if I can get a spare one.

[mon2]

Re: Asus X512F won't hold on battery charge

Yes, agreed. Test with a known good battery. Perhaps you can get it from your local Amazon stores? Then return it if it is not required.

[Kambi13]

Re: Asus X512F won't hold on battery charge

Hi all, final update on this one, and when you thought you've seen it all, something new will prove you wrong. So yesterday I had a costumer that brought an Asus laptop for a screen replacement, while working on it saw that the battery pack, although different in shape had the same connector and rating, so I thought, why not? let me try this one.
So I plugged it in and pressed the power button, the power led came on, and after a few seconds it started flashing white along with the battery led, nothing came up on screen, turned it off and tried again, same result, though the cpu cooler was getting warm!!! Well no good I guess, so I removed the battery and tried to plugged it with the charger alone, this time only the power led was flashing because there was no battery in of course, but what the hell!? Now it doesn't even work with the charger!!!! It used to... Was about to throw the laptop out the window but I just let it sat for a while with everything disconnected.
After 10 minutes tried to plug in the charger and this time it power cicled, power led light now solid white and after a few seconds it booted up, sigh of relief, it's still working
Turned it off again, plugged in original battery, turn on again, boots up, gets into windows and this time I'm getting info on remaining charging time until it's full... Unplugged the charger and it dind't turn off, it's holding on battery charge!!!! What the actual FU$%K, it charged to 100% after a couple of minutes. Now its fully working, even tried again the battery from the other Asus laptop and it worked perfectly.
So, bottom line, some neurons burnt for nothing...