HP 15-dc DAG3DDMB8C0 problem power up with battery.

[quic307]

Hi techs,

I have the HP 15-dc DAG3DDMB8C0 rev C.

When I have the battery (without the power adapter) it doesn't power up. The first time I put the new battery in it will power up, but after few seconds nothing. I insert a second new battery and after few second same ...
I'm looking for a short circuit, I can't find it.
With the power supply is fine but it does not charge the battery.

I need help please ...

Thanks a lot...

[mon2]

Re: HP 15-dc problem power up with battery.

Link the schematic if available.

Post the voltage with the adapter and battery connected of every pin on the battery connector. Start here.

[quic307]

Re: HP 15-dc problem power up with battery.

No shematic available
I made 3 measurments with the adapter connected
with "new" battery
pin1 Gnd
pin2 Gnd
pin3 0
pin4 3,13
pin5 3,10
pin6 3,10
pin7 13,8
pin8 13,8

without battery
pin1 Gnd
pin2 Gnd
pin3 3,15
pin4 3,27
pin5 3,21
pin6 3,21
pin7 3,08
pin8 3,08

with the old dead battery
pin1 Gnd
pin2 Gnd
pin3 0
pin4 3,29
pin5 3,13
pin6 3,13
pin7 1,11
pin8 1,11

So pins 5 & 6 are the data communication pins and they are stable [they both have the same value of resistor connected]
pin 4 seems to be different from pins 5 & 6 as it has a low resistor [just 100 Ohms] - maybe is for suppling the 3 volts olny?
pin3 is the battery detection pin and goes to zero when battery is present - it connects to pin120 of kbc

pin7 & 8 are the positive of the battery, non of the two batteries gives voltage without the power adapter and when connecting the power they take different charge voltage in order to charge but they don't as voltage remains stable

[mon2]

Re: HP 15-dc problem power up with battery.

The mosfets mated with the charger IC need to be reviewed. While they are passing through the voltage to the logic board, you likely have defective mosfets.

Look near the dcin adapter connector to locate the battery charger. What are the markings on the topside of the charger IC?

Start with, remove all power / no battery.

Meter in resistance mode.

Measure the resistance of each of the 2 x dcin mosfets as follows:

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 and the meter scale used.

Repeat for the next mosfet.

You will find 3 other mosfets that will be for the battery charging and that connects the battery to the logic board.

Also interested in the measurements of those mosfets which are high side, low side and battery mosfets.

One or more of these is leaking. The measurements will tell us which one is defective.

No power when checking the resistance values.

[quic307]

Re: HP 15-dc problem power up with battery.

the charger is BQ24738H
meter has auto scale, 2 measurements by flipping positive & negative probes
first dcin mosfet [2 in parallel]
S & D 7,25M 4,45M
S & G 10,77M open line
G & D 23,27M open line

second dcin mosfet
S & D 3,91M 3,43M
S & G 10,73M open line
G & D 15,06M open line

high side charge
S & D dropping from over 10M close to 6M either side
S & G 193K 48K
G & D 2,3M droppin around 5M

low side charge
S & D 6,8M 5,1M
S & G 142K 46K
G & D 4,3M 5,5M

battery mosfet
S & D 1,05M dropping from over 10M close to 6M
S & G 6,6M open line
G & D 2,7M open line

at all battery mosfets the measurements constantly change more or less

[mon2]

Re: HP 15-dc problem power up with battery.

Replace your high side and low side battery mosfets and test again. The resistance in the low kohms is considered too low.

[mcplslg123]

Re: HP 15-dc problem power up with battery.

I dont think High/Low side fets are defective. Better if you can give voltage on all charging Pins.

[quic307]

Re: HP 15-dc problem power up with battery.

I change battery from other store and now works.
Thank you for your time.