Charging IC BQ24736 ILIM Question

[psdavid65]

Hi there. Could someone kindly assist me with how much voltage in needed on Pin number 10(ILIM) and Pin 11(DLIM) for standard operation of the laptop. I have 3.3V on ILIM and 0 Volts on DLIM. Are these voltages normal? what will happen is ILIM is 0 volts? What will happen if DLIM is 3.3V

IC is BQ24736

[mon2]

Re: Charging IC BQ24736 ILIM Question

What is the fault of your logic board?

If ILIM is > 1v6, then the charger will charge at the highest current. These are the details from similar but public charger datasheets by Texas Instruments.

[psdavid65]

Re: Charging IC BQ24736 ILIM Question

The logic board is an HP 1040 G2 which doesn't charge. Battery is always at 0%. Unfortunately this model doesn't have a schematic but this is what I have found so far.
Switching is perfect on blocking and switching mosfets. 1st P channel mosfet has 6volts on gate and second N channel mosfet has 25 volts on gate.
ACP, ACN, CMSRC are both 19volts.
ACDRV has 25 volts
ACOK has 3.3V
ACDET has 2.6V
REGN has 6V
BTST has 5.93volts
SCL 3.15V
SDA 3.3V
ILIM 3.3V
DLIM 0V
IOUT 0V
SRP 1.8V
SRN 1.8V
PHASE 1.8V
HIDRV 1.8V
LODRV 0V

The N channel charging mosfets for the battery has been checked in resistance mode and resistance is okay. There is no short between Drain and Source, Source to Gate and Gate to Source. No short. The same applies to the P channel battery discharge mosfet. On the P Channel battery discharge mosfet, Gate and source are both 19V and Drain(battery positive side) is 1.8V
SDA and SCL lines has 3.3v and 3.15 respectively on battery connector pins on the motherboard. The resistors for the SDA and SCL on the battery connector side are 100R, and the resistors for SDA and SCL from pin 12 and 13 on BQ24726 IC are 4.7K respectively.
All these voltages are present without battery connected.
With battery connected, the voltages are still the same. If I charge the battery externally and plug it in the motherboard, the laptops powers on but still doesn't charge. With an EXTERNALLY charged battery connected, Drain of P channel battery discharge mosfet becomes 10.80 volts but battery doesn't charge. I have replaced the laptop battery 3 times.

[psdavid65]

Re: Charging IC BQ24736 ILIM Question

The closest schematic to this is HP 4340S and they use the same power scheme and same BQ24726 IC

[mon2]

Re: Charging IC BQ24736 ILIM Question

Very good review.

Is the charger IC onboard the BQ24726 or BQ24736?

Post a pic of the charger IC. How many pins?

Suggestion is to connect the adapter only, carefully measure the voltage to ground of each pin on the charger IC.

Connect both the adapter and battery to the unit and measure again the voltage to ground of each pin on the charger IC.

Post both sets of measurements.

Is the battery detected by the host logic board? Confirm the battery connector is solid.

Confirm the voltage to ground of the smbus lines (SCL and SDA pins) on the battery connector. These must be operational to extract the battery details from the bms inside the battery pack. Be sure the battery packs are truly compatible for this laptop else it can be rejected.

With a low cost tool like Arduino, you can extract the smbus based battery pack parameters.

When a charged battery is mated with the board, what is the voltage to ground of SRP and SRN? Where are you measuring these current sense pins?

[psdavid65]

Re: Charging IC BQ24736 ILIM Question

Hi Mon2. Thank you so much for the quick reply.
The charging IC is BQ24736 but I think its the same as BQ24726
Quick update, after getting another battery from a similar model, the battery began to charge.

[mon2]

Re: Charging IC BQ24736 ILIM Question

As @Piernov has stated and I did disagree with, early on, 99% of the time, the fault is the battery. Lots of crapware out there. If available, try to test and source with products from Amazon so that you have some way to return the battery if it is not a good fit.

[psdavid65]

Re: Charging IC BQ24736 ILIM Question

Thank you for your advice Mon2. I'm really glad you took time off your busy schedule to assist me. Bless you