LA-D711P Not charging battery

[ResoluteHawk]

So I can't seem to get this board to charge the battery. Inside Windows it shows the battery as detected but the battery never charges.

AC adapter outputs 19v and when plugged in with the battery in, the charging light turns orange, which normally indicates that the battery is charging. Without the battery the light is white, as it should be.

If I look at the board and specifically the battery charging IC which in this case on my board is BQ25A; I'm pretty sure that all of the voltages read out correctly.
There are no shorts that I can measure in the MOSFETS around the battery area, and if measured in Ohms mode they all read in the kOhm and mOhm ranges.

EC_SMB_CK1 and EC_SMB_DA1 both measure 3.3v.

Could this be a simple case of a bad battery? What am I missing?

[mon2]

Re: LA-D711P Not charging battery

Hi.

1) can you post or link the schematic ?

2) If not available, share all silk screen markings on the logic board which may assist to track down the schematic.

3) Is the battery now dead with no voltage? What voltage do you see on the battery after attaching to the logic board and using the recommended power adapter?

4) Be sure the adapter is the recommended one and suitable for this unit. If it is under powered, the battery will not be charged.

5) Did the battery work in the past? How old is the battery? Yes, testing another battery is recommended. You could source one from Amazon and return it if the symptoms are the same. You will have some time to test out other ideas.

6) Post the full markings of the charger IC so we can locate the datasheet or an example schematic to study.

[ResoluteHawk]

Re: LA-D711P Not charging battery

The board schematic that I'm using for reference is the one attached.

It's not for the exact same board, but a lot of the components are similar and the connections seem to be relatively the same.

If I disconnect AC power while the system is running, the laptop shuts off, which makes me think that the battery is completely dead. We just got the battery in for a customer about 2 weeks back and it was brand new.

The AC adapter is the one that originally came with the laptop, and it matches the input needed on the laptop.

I'm looking specifically at pages 39 and 40 on this particular schematic.

[mon2]

Re: LA-D711P Not charging battery

Ok. See attached.

Start with the basics, let us confirm the 2 x DCin mosfets.


Attach the adapter and also the battery pack.

Confirm the voltage to ground of:

ACDRV pin # 4
ACOK pin # 5
REGN pin # 16


of the charger IC @ PUB1.

If all is well, the ACDRV pin should be a boosted voltage of ~25 volts to enable the 2 x DCin mosfets. If it is not, then remove the 4k series resistor @ PRB8. Then check again the voltage of ACDRV pin on PUB1.

Do you see ~25 volts now ? (ACDRV = adapter in + REGN of 6 volts = ~25v)

After the above confirmation, we need to check the condition of the other mosfets mated to PUB1.

You can do this with resistance checks.

Remove all power / no battery.

Meter in resistance mode.

Check the resistance across the following mosfet pins:


SOURCE (9) & DRAIN1 (2-3-4-10)
SOURCE (9) & GATE1 (1)
GATE1 (1) & DRAIN1 (2-3-4-10)
; HIGH SIDE charge mosfet

SOURCE (5-6-7) & DRAIN2 (9)
SOURCE (5-6-7) & GATE2 (8)
GATE2 (8) & DRAIN2 (9)
; LOW SIDE charge mosfet


SOURCE (1-2-3) & DRAIN (5-6-7-8)
SOURCE (1-2-3) & GATE (4)
GATE (4) & DRAIN (5-6-7-8)
; BATTERY mosfet @ PQB3


Post each measure and the meter scale used for the test.

Do this for mosfets:

PQB4 ; DUAL mosfet in a single package
PQB3 ; BATTERY mosfet

If the battery is connected and is being detected, the CHARGE voltage should be present @ PLB2, pin #2. Is it ?

Does Windows report the presence of the battery? Battery charge graphic?

[ResoluteHawk]

Re: LA-D711P Not charging battery

I think I found the issue. Apparently there are two different batteries that are made for this model.

Customer had an 11.1v I believe and we ordered a 14.8v battery, but we should have ordered an 11.1v battery because the 14.8v is "not compatible" with the 11.1v version of the laptop???
I don't really understand how this would cause an issue with the battery not charging other than maybe the charger doesn't have enough voltage to charge the battery, but this seems like nonsense since the 14.8v of the battery is less than the 19.5v from the charger, therefore the battery should still charge.

I guess I'm confused.

Does Windows report the presence of the battery? Battery charge graphic?

Yes Windows shows that a battery is installed, but not charging. It just says plugged in.

[mon2]

Re: LA-D711P Not charging battery

Each battery pack contains a BMS (battery management system) module. Within this module is a SMBUS slave controller that spits back data such as serial #, brand, charge current, etc. and a SMBUS address. Using this dedicated address, the BMS module can be indexed for communication.

It is very possible that the other battery pack you have is using a different SMBUS address or charge voltage or charge current so is not charging.

Using an Arduino, you can extract the above details using the same SMBUS interface.

Using a low cost bus analyzer, you can monitor the traffic between the battery and the host logic board to view the communication taking place between the 2 parties.

[ResoluteHawk]

Re: LA-D711P Not charging battery

That's what I thought too, but at the same time I've replaced batteries with higher voltage ones and they still charged. I guess this is one that's different.

I'll still measure those voltages tomorrow and report back.

[ResoluteHawk]

Re: LA-D711P Not charging battery

AC Adapter and Battery both installed.

PUB1
Pin #4 (ACDRV) => 25v
Pin #5 (ACOK) => 3.3v
Pin #16 (REGN) => 6v

AC Adapter and Battery Out

SOURCE (9) & DRAIN1 (2-3-4-10) => 7.35M Ohms (Manual 10M Ohms)
SOURCE (9) & GATE1 (1) => 26K Ohms (Manual 100K Ohms)
GATE1 (1) & DRAIN1 (2-3-4-10) => VERY TINY AREA SO CAN'T MEASURE WITHOUT TAKING OFF PL16
; HIGH SIDE charge mosfet

SOURCE (5-6-7) & DRAIN2 (9) => Somewhere between 1M Ohm and 10M Ohms (Manual 100M Ohms)
SOURCE (5-6-7) & GATE2 (8) => 140K Ohms (Manual 1000K Ohms)
GATE2 (8) & DRAIN2 (9) => Again the reading seemingly lies somewhere in the 1-10 mOhms range.
; LOW SIDE charge mosfet


SOURCE (1-2-3) & DRAIN (5-6-7-8) => 7M Ohms (manual 10M Ohms)
SOURCE (1-2-3) & GATE (4) => 3.93M Ohms (Manual 10M Ohms)
GATE (4) & DRAIN (5-6-7-8) => 7.3M Ohms (Manual 10M Ohms)
; BATTERY mosfet @ PQB3

AC Adapter Plugged In
Pin#2 on BQ25A => 19.64V

[mon2]

Re: LA-D711P Not charging battery

Remove the dual charging mosfet and measure again or just replace it.

Some of these readings are considered to be low (ie. Source / Gate).

Test again with the replacement. If required, can try to find a replacement from Digikey / Mouser.

Post your updates.

[ResoluteHawk]

Re: LA-D711P Not charging battery

So we got the replacement battery in (11.1v) and slapped it in the laptop. Charges just fine.

This issue really came down to an incompatibility between two batteries for the same laptop.

That's a first for me. Didn't know that could happen.