macbook A1502 not charging if battery is at 0

[dclass-pro]

Hi guys,
I have a macbook A1502 that does not charge if the battery is completely discharged!!
If I unplug it and reconnect it to the motherboard it starts to charge well, and it charges up to 100% and works.
If I let the battery completely discharge, and connect the charger, the magsafe2 LED turns orange but it never charges the battery.
What do you recommend I try?
I tried to change the battery with a new one and the problem did not solve it
Code mainboard 820-3476-A

[mon2]

Issue may be with a defective Q7155.

[dclass-pro]

I tried to change it but the problem persists, the charger LED is orange but the macbook doesn't turn on and the fan doesn't start, if I leave it connected it actually charges the battery but the mac doesn't turn on, it only turns on if I disconnect and reconnect the battery

[mon2]

Is the power adapter the original and suitable to power this model?

[dclass-pro]

the power supply is original but I also tried with my bench power supply, I have a current draw of 2.3A because it charges the battery but if I press the power button it doesn't turn on, if I disconnect the battery and reconnect it then yes, it turns on

[mon2]

Disconnect the battery. Attach only the original OEM power adapter.

Measure the voltage to ground of:

SMBUS_SMC_5_G3_SCL
SMBUS_SMC_5_G3_SDA

Post each measurement. You can measure these at the battery connector on the logic board.

[dclass-pro]

SMBUS_SMC_5_G3_SCL - 3,4V
SMBUS_SMC_5_G3_SDA - 3,4V

[mon2]

No issue here.

Measure the voltage to ground on each pin of D7005 with only the power adapter.

[dclass-pro]

PIN1 = 18,64V
PIN2 = 12,68V
PIN3 = 18,40V

[mon2]

Power down. No power / no battery.

Meter in resistance mode (not diode mode). Measure the resistance directly on the charger IC @ U7100 with one meter lead on pin # 17 and other meter lead on pin # 18. This measurement should be ~2-3 ohms. Confirm it. This is the battery charge current sense loop resistance.

[dclass-pro]

Have 4.5ohm

[mon2]

Short your meter probes. What is the resistance? This is your baseline for your meter.

Next, measure the resistance across:

resistor R7151 - should be ~2 ohms.
resistor R7152 - should be ~0 ohms.

[dclass-pro]

resistor R7151 - 2,4ohm
resistor R7152 - 0,3 ohms.

[mon2]

Test your dual mosfet @ Q7130 and also Q7180.

Measure the resistance (without power to the board) of:

source / drain
source / gate
gate / drain

of each internal mosfet. Checking if one of the mosfets is leaky.

[dclass-pro]

I confirm that the dual mosfets @ Q7130 and also Q7180 are not predictive, I compared them with another recovery board that I have here in the lab and they are the same, do you advise me to change the charger?

[Sancho Marcelino]

Possible Causes

SMC (System Management Controller) Bug	Sometimes SMC does not properly detect a fully discharged battery	Reset SMC & PRAM
PPBUS_G3H Voltage Drop	If PPBUS_G3H is too low, charging does not start	Check PPBUS_G3H (Must be ~12.56V-12.6V)
Corrupt Battery Data / SMBUS Issue	Battery is not properly detected when completely discharged	Check SMBUS Lines (SCL & SDA) on battery connector
Defective Charging MOSFETs (Q7150 / Q7130)	If the FETs controlling charging are faulty, battery won't charge at low voltage	Check Q7150 / Q7130 for shorts or low resistance
Defective U7000 (Charging IC - ISL6259)	This IC manages charging and might not handle deep discharge states correctly	Check U7000 input/output voltages

Step-by-Step Troubleshooting

Reset SMC & PRAM

• SMC Reset:
  1. Turn off the MacBook.
  2. Hold Shift + Control + Option + Power for 10 seconds.
  3. Release and power it on normally.
• PRAM Reset:
  1. Turn off MacBook.
  2. Hold Command + Option + P + R while turning it on.
  3. Keep holding until you hear the startup chime twice.

Test again. If the issue persists, continue troubleshooting.

Measure PPBUS_G3H Voltage

• PPBUS_G3H should be ~12.56V-12.6V.
• If PPBUS_G3H is below 12.3V, the charging circuit isn't providing enough power.
• If voltage is low, check Q7150, Q7130, and U7000.

Check SMBUS (Battery Communication)

• Measure SCL (Clock) and SDA (Data) lines at battery connector.
• Expected values:
  • SCL & SDA: ~3.3V when battery is connected.
• If missing or fluctuating, check R7051/R7052 pull-up resistors (3.3kΩ).

Check Charging MOSFETs (Q7150 & Q7130)

• Measure resistance across Q7150 / Q7130.
• If resistance is very low (~0Ω), the MOSFET is shorted.
• Replace faulty MOSFET if necessary.

Check U7000 (Charging IC)

• Measure voltages at U7000:

  Pin 2 (ACIN)	~3.42V
  Pin 17 (BATDRV)	~12.6V
  Pin 20 (CHGR_EN)	~3.3V

• If BATDRV is missing, U7000 isn't enabling charging.
• If U7000 gets very hot, replace it.

Final Fix Recommendation

• If resetting SMC/PRAM fixes it temporarily → Consider replacing U7000.
• If PPBUS_G3H is low → Check Q7150 / Q7130 MOSFETs.
• If SMBUS signals are missing → Check battery connector & R7051/R7052 resistors.
• If nothing else works → Replace U7000 (ISL6259).

[dclass-pro]

Good morning, thanks for the reply, I changed both U7000 and Q7130 but on PPBUS_G3H when I connect the caticator I always have 10.7V but never 12.5V.. what can I try to see?

[Sancho Marcelino]

Alright! Since you've already replaced U7000 (CD3215/17) and Q7130, but PPBUS_G3H is stuck at 10.7V instead of 12.56V.

This issue suggests that U7000 is unable to generate the correct PPBUS_G3H voltage, which means we need to troubleshoot power regulation, feedback circuits, and load issues.

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Troubleshooting for PPBUS_G3H Low Voltage Issue

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Check U7000 (CD3215/17) VIN & Power Rail Behavior

• U7000 is responsible for USB-C communication and power delivery negotiation. If it doesn't communicate properly, it won't enable PPBUS_G3H correctly.
• Measure VIN (pin depends on the boardview)
  • If it's 20V, it's negotiating correctly.
  • If it's 5V, the USB-C PD handshake may have failed.
• Check PPDCIN_G3H
  • Should be 20V before entering Q7130.
• Confirm if U7000 is sending an enable signal for Q7130.

If U7000 is not sending the enable signal, try reflowing or replacing it again.

---

Check Q7130 Gate Drive

• Q7130 is a MOSFET that helps switch PPDCIN_G3H (20V) to PPBUS_G3H (12.56V).
• Measure Gate Voltage:
  • If the gate is not switching properly, Q7130 won't fully open, which can cause voltage drop (10.7V instead of 12.56V).
• Expected values:
  • Drain (PPDCIN_G3H) → 20V
  • Source (PPBUS_G3H) → 12.56V
  • Gate → Must be lower than Source to turn on.
  • If Gate is too high, Q7130 stays OFF.
  • If Gate is too low, Q7130 might be shorted.

If the Gate is not switching, check the pull-down resistor and gate driver circuit.

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PPBUS_G3H Line Load Test (Is Something Pulling Voltage Down?)


Sometimes, a bad component downstream of PPBUS_G3H causes excessive current draw, which lowers voltage.

• Measure current draw from PPBUS_G3H:
  • Use DC bench power supply and set 12.56V @ 1A.
  • Inject voltage into PPBUS_G3H and check if voltage still drops.

If PPBUS_G3H stays low when injecting voltage, you may have a bad component pulling power.

Test each component connected to PPBUS_G3H:

• Capacitors (C7050, C7055, C7052, etc.) → Look for shorted or leaky caps.
• Coils (L7030, L7035, etc.) → Measure voltage drop.
• Downstream regulators (e.g., CPU/GPU buck converters) → If they're pulling too much power, the whole line may drop.

If one of these components is causing a drop, desolder it and test again.

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Feedback Circuit - Voltage Divider Resistors


U7000 uses feedback resistors to regulate PPBUS_G3H output.
If these resistors fail (wrong resistance or open circuit), U7000 won't regulate properly.

Check these key resistors:

• R7005, R7006 – Main voltage feedback divider.
• Measure with a multimeter (compare with known good board if possible).
• If resistance is too high or open, replace it.

If feedback resistors are bad, U7000 won't know how to adjust PPBUS_G3H, causing low voltage.

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Check SMC Power Control


The SMC (System Management Controller) enables PPBUS_G3H via U7000.
If SMC is not properly enabling the circuit, you may get partial power (10.7V instead of 12.56V).

Check for SMC enable signal:

• SMC_LID – Lid sensor signal.
• PM_EN_P3V3_G3H – Enables 3.3V power rail.
• PPBUS_G3H_ENABLE – Check if this signal is present.

If SMC is not sending an enable signal, check for corrupted firmware, or reflow/reprogram SMC.

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U7000 I2C Communication Issue (Advanced Debugging)


U7000 communicates with the logic board via I2C bus. If this communication fails, it may not generate the correct voltage.

Check I2C lines:

• I2C_SCL (Clock Line) → Should show pulses on oscilloscope.
• I2C_SDA (Data Line) → Should have data communication.
• If no signal → U7000 may be faulty, or I2C bus may be damaged.

Reflash or replace U7000 if necessary.

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Summary - What to Check Next

U7000 VIN	20V	If 5V, PD negotiation failed. Check U7000.
PPDCIN_G3H	20V	If low, check Q7130 or upstream power.
Q7130 Gate Drive	Proper switching	If gate is too high/low, check gate resistor or driver.
PPBUS_G3H Load Test	No excessive draw	If voltage drops, locate shorted component.
Feedback Resistors (R7005, R7006)	Correct resistance	If open or wrong value, replace them.
SMC Enable Signals	Present	If missing, check SMC firmware or reflow SMC.
I2C Bus Communication	Normal data activity	If missing, check U7000 or I2C lines.

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[dclass-pro]

thank you for the explanation but the macbook is an A1502 and does not have usb-c

[Sancho Marcelino]

Oh, sorry! Are you still having issues with your Mac?