macbook A1502 not charging if battery is at 0

[mon2]

Post # 12

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

[reformatt]

PPBUS_G3H =12.6V when battery is disconnected. Will drop to whatever the battery voltage is when connected.

PM_BATLOW_L is something to check. Often stuck low with a non-genuine or under rated charger and a flat battery. A1502 need a 60W genuine charger to properly troubleshoot. This signal derived from the SMC via the one-wire comms to the charger.

[dclass-pro]

Hi guys, sorry for my absence but I wasn't in the lab, yes I'm still having problems and I can't figure out where it's coming from.
What do you recommend I check?

[mon2]

Catch up on the requested measurements.

[dclass-pro]

on the PPBUS_G3H I have 10.11V without the charger connected, when I connect the charger I have about 11V which increases very very slowly
I confirm that with the battery disconnected on PPBUS_G3H I have 12.65V

[dclass-pro]

on pin ADAPTER_SENSE have 2.8v

[mon2]

Post #22.

What is the voltage to ground of PM_BATLOW_L?

[dclass-pro]

PM_BATLOW_L is 3.34V without battery connected, but only with charger connected

[mon2]

So the board is OK with your power adapter.

Post #21 - meter in resistance mode. If manual meter, select the lowest resistance scale. Touch your meter probes together. What is the measurement in ohms?

[dclass-pro]

if I short circuit the tester probes the value I get is 0.3ohm

[Sancho Marcelino]

on the PPBUS_G3H I have 10.11V without the charger connected, when I connect the charger I have about 11V which increases very very slowly
I confirm that with the battery disconnected on PPBUS_G3H I have 12.65V

Advanced Troubleshooting for PPBUS_G3H Voltage Drop on MacBook A1502 (820-3476-A)


Since you're getting only 10.11V on PPBUS_G3H with the battery connected, but a normal 12.65V with the battery disconnected.

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Step 1: Identify the Main Issue

Battery disconnected, charger connected	12.65V (Normal)	Charging circuit (U7000, Q7130) is likely functional.
Battery connected, no charger	10.11V (Low)	Battery might be faulty or there's excessive current draw.
Battery connected, charger connected	~11V (slow increase)	Power management circuit (U7000, SMC, Q7130) might not be regulating properly.

Since PPBUS_G3H is fine without the battery, the issue is likely related to:

• A failing battery (high internal resistance, not accepting charge)
• U7000 (Charging IC) failing to regulate power properly
• Q7130 (Charging MOSFET) not switching correctly
• Excessive current draw from a short or leakage on PPBUS_G3H

---

Step 2: Measure Key Voltages & Signals


To pinpoint the issue, we need to measure key signals around U7000 (ISL6259), Q7130 (Charging MOSFET), and SMC communication lines. ✅ Test 1: Measure U7000 (ISL6259) Input & Output

Pin 1 (DCIN, PPDCIN_G3H)	16.5V - 18.5V	?	If missing, charger is not supplying power.
Pin 2 (CHGR_ACOK)	3.3V	?	If 0V, U7000 doesn't detect charger.
Pin 17 (BATGATE)	12.6V	?	If low, battery isn't being charged.
Pin 20 (PPBUS_G3H Output)	12.56V	10.11V	Regulation issue inside U7000.
Pin 27 (CHGR_BMON, Battery Current Monitor)	Varies	?	If 0V, battery might not be charging.

If CHGR_ACOK = 0V, U7000 is not detecting the charger properly.
If BATGATE = 0V, U7000 is not enabling the battery charge circuit.

Possible Fix: If signals are missing, reflow or replace U7000 (ISL6259).

---

Test 2: Check Q7130 (Charging MOSFET)

Drain (PPDCIN_G3H, Charger Input)	16.5V - 18.5V	?	If missing, charger isn't supplying power.
Source (PPBUS_G3H Output)	12.56V	10.11V	MOSFET might not be switching properly.
Gate (Driven by U7000)	8V - 12V	?	If low, Q7130 might not be turning on.

If Q7130 is not switching correctly, it may limit power to PPBUS_G3H.
Possible Fix: If gate voltage is low, replace Q7130.

---

Test 3: Check for a Partial Short on PPBUS_G3H


Since PPBUS_G3H is dropping to 10.11V when the battery is connected, check if there's a partial short or excessive current draw. 🔍 How to Check for Shorts

1. Measure resistance to ground on PPBUS_G3H.
   • Normal resistance: 10kΩ+
   • If very low (below 50Ω), there's a short.
2. Use a thermal camera or alcohol method.
   • Apply isopropyl alcohol on the board and power it.
   • Look for a component heating up unexpectedly (a shorted capacitor or MOSFET).

Possible Fix:

• If a capacitor is shorted (e.g., C7010, C7020), remove and replace.
• If PPBUS_G3H rail is leaking power, trace with a thermal camera.

---

Step 3: Advanced Debugging

Check SMC Communication (If Battery Not Charging)


The SMC (System Management Controller) tells the MacBook when to charge the battery. If SMC is not sending correct signals to U7000, the battery might not charge.

1. Check SMC_BC_ACOK (SMC to U7000 Communication)
   • Should be 3.42V
   • If 0V, SMC might not be detecting the charger.
2. Try an SMC Reset
   • Press Shift + Control + Option + Power for 10 seconds then release.
   • If charging improves after a reset, the SMC might be at fault.
3. Check for Corrosion Near SMC
   • Pins to inspect: SMC_LID, SMC_BC_ACOK, SMC_RESET_L
   • If corroded, clean and reflow.

Possible Fix:

• If SMC signals are missing, reflash or replace SMC.

---

Summary – Step-by-Step Fix

🔹 Step 1: Check Battery First

• Measure battery voltage at the connector.
  • If below 11V, battery might be dead. Try another battery.
• Check battery resistance.
  • If resistance is too low, there could be an internal short.

🔹 Step 2: Measure U7000 (Charging IC)

• Check CHGR_ACOK, BATGATE, CHGR_BMON
  • If missing, U7000 might be faulty. Reflow or replace.

🔹 Step 3: Check Q7130 (Charging MOSFET)

• If PPBUS_G3H drops when battery is connected, MOSFET might not be switching correctly.
• Measure Source, Drain, and Gate voltages.

🔹 Step 4: Check for Shorts on PPBUS_G3H

• Measure resistance (should be 10kΩ+).
• Use a thermal camera or alcohol to find heating components.

🔹 Step 5: Inspect SMC Communication

• Check SMC_BC_ACOK (should be 3.42V).
• Try an SMC Reset.
• Inspect for corrosion on SMC signals.

Most Likely Fixes Based on Symptoms:

1. Faulty Battery – If voltage is too low, replace it.
2. Bad U7000 (Charging IC) – If signals are missing, reflow or replace.
3. Faulty Q7130 (MOSFET) – If gate voltage is incorrect, replace.
4. Partial Short on PPBUS_G3H – If resistance is low, locate and remove the faulty component.
5. SMC Issue – If signals are missing, reflash or replace SMC.

[Sancho Marcelino]

PM_BATLOW_L is 3.34V without battery connected, but only with charger connected

MacBook A1502 (820-3476-A) Battery & Charging Issue

• PM_BATLOW_L = 3.34V with charger, no battery → Normal behavior (since it's pulled up to 3.42V).
• PPBUS_G3H is too low (~10-11V with charger, 12.65V without battery) → Charging circuit issue.
• Battery does not charge when completely discharged.

---

Step-by-Step Deep Diagnosis

Step 1: Check Charger & Adapter Sense Circuit (ADAPTER_SENSE)

• You measured ADAPTER_SENSE = 2.8V.
• Normal range should be around 3.3V.
• If ADAPTER_SENSE is too low, the MacBook might be misreading the charger wattage → throttling charging power.

What to Check?

1. Measure voltage on R7011 (1.87MΩ) & R7012 (1.1MΩ) divider.
   • These resistors create the ADAPTER_SENSE voltage.
   • If one is bad, it can cause incorrect charger recognition.
2. Check U7000 (ISL6259) pin 6 (ACIN).
   • If this voltage is abnormal, charging logic is affected.

---

Step 2: Measure & Inspect U7000 (ISL6259) - Charging Controller

• U7000 is the main charging IC, regulating PPBUS_G3H.
• If PPBUS_G3H is unstable (10-11V), U7000 might be faulty or missing an enable signal.

What to Check?

1. Pin 2 (DCIN) → Should match charger voltage (~16.5-20V).
2. Pin 5 (ACOK) → Must be HIGH (~3.4V) for charging to enable.
3. Pin 17 (CHGR_ACOK) → Should be HIGH (~3.4V) to indicate charger is valid.
4. Pin 20 (BATDRV) → Must be HIGH for battery charging to activate.
5. Pin 27 (PPBUS_G3H) → Must be 12.6V under normal conditions.

If ACOK = 0V → U7000 does not recognize the charger.
If CHGR_ACOK = 0V → The charger is not seen as valid.
If BATDRV = LOW → U7000 is not enabling battery charging.

---

Step 3: Check Q7130 (Chargers MOSFET)

• Q7130 (SMC 7051) is a MOSFET that controls current flow to PPBUS_G3H.
• If Q7130 is faulty, PPBUS_G3H will be too low, affecting battery charging.

What to Check?

1. Measure voltage at Q7130 Drain (PPBUS_G3H side) → Should be 12.6V.
2. Measure Q7130 Gate voltage:
   • If Gate is LOW (~0V) → U7000 is not enabling Q7130.
   • If Gate is HIGH (~20V) but Drain is low → Q7130 is defective.

If Q7130 is bad, replace it with a known good one.

---

Step 4: Check SCL/SDA (Battery Communication)

• The battery communicates with the SMC via SMBUS (SCL/SDA lines).
• If communication fails, the battery won't charge properly.

What to Check?

1. Measure voltage on SCL (Clock) and SDA (Data).
   • Both should be ~3.3V when idle.
   • If both are 0V, there's a short or SMC is not pulling them up.
   • If one is 0V and the other is 3.3V, check the pull-up resistor on the low line.
2. Check R5421 & R5422 (3.3kΩ pull-up resistors for SCL/SDA).

If SMBUS is bad, the MacBook won't recognize the battery, even if it's good.

---

Step 5: Thermal & Short Circuit Check


If all voltages seem correct but the issue persists:

1. Use IPA (Isopropyl Alcohol) or Thermal Camera to check for hot components near U7000, Q7130, or the battery circuit.
2. Check resistance to ground on PPBUS_G3H:
   • Normal: 6-8 kΩ.
   • If < 1 kΩ, there's a possible short (faulty capacitor or MOSFET).

---

1. Reconnect the battery and measure PM_BATLOW_L again.
2. Check U7000 (ISL6259) pins 2, 5, 17, 20, 27.
3. Measure Q7130 Drain and Gate voltages.
4. Check SCL/SDA lines for battery communication.
5. Check for heat or short circuits using IPA or thermal imaging.

[dclass-pro]

Hi and thanks for the very detailed guide, but I started checking these points:
"You measured ADAPTER_SENSE = 2.8V.
The normal range should be around 3.3V.
If ADAPTER_SENSE is too low, the MacBook may misread the power of the charger → limiting the charging power.
What to check?
Measure the voltage on the divider R7011 (1.87MΩ) and R7012 (1.1MΩ)."
but on my schematic R7011 is 10k and R7012 is 68K, I don't know if the guide is reliable.
Thanks

[Sancho Marcelino]

Data Analysis & Test Point Isolation – MacBook A1502 (820-3476-A) Battery Won't Charge After Full Discharge


This guide will use data-driven testing and precise test point measurements to isolate the root cause of the issue.

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Problem Breakdown & Failure Mode Analysis

Battery charges after manual reconnection	SMC detects battery, U7000 enables charging	SMBus failure, battery low protection triggered, or wake-up issue
Battery does NOT charge after full discharge	U7000 should initiate charge cycle	SMC ignores deep-discharged battery, CHGR_BMON failure, or U7000 misfire
MagSafe LED turns orange	Charger is detected	U7000 failing to enable battery charging, or incorrect PM_BATLOW_L

---

Data Analysis & Test Points

Step 1: Battery I²C Communication (SMBus Analysis)

Test: Capture I²C Communication on SMBus


Test Points:

• SMBUS_SMC_5_G3_SCL (Clock)
• SMBUS_SMC_5_G3_SDA (Data)

Perform Test:

• Use oscilloscope or logic analyzer to capture SMBus activity.
• Expected Data:
  • 100kHz square wave on both lines when battery is connected.
• Abnormal Readings:
  • Both lines stuck HIGH (3.3V) → Battery not responding.
  • Both lines stuck LOW (0V) → Short circuit on SMBus.

If No SMBus Activity:
Check Pull-up Resistors:

• R5421 (3.3KΩ) - SCL Pull-up
• R5422 (3.3KΩ) - SDA Pull-up
• If resistors are open, replace them and retest.

Force Inject 3.3V on SDA (Wake-Up Test):

• If this restores communication, the battery EEPROM is failing to wake up.

---

Step 2: Battery Charging Current Analysis (CHGR_BMON)

Test: Monitor Battery Current Flow


Test Points:

• CHGR_BMON (Pin 20 on U7000)
• PPBUS_G3H (Main Power Rail - 12.56V)

Perform Test:

• Use a Multimeter (DC Voltage Mode):
  • Expected: CHGR_BMON = 0.8V - 1.2V during charging.
• Oscilloscope Analysis:
  • Should show voltage fluctuations as charge current varies.

If CHGR_BMON is Stuck at 0V:
Check Shunt Resistor R7150 (0.005Ω):

• This resistor allows U7000 to measure current flow.
• If open or burned, U7000 won't detect current and charging will fail.

Check for Trace Damage:

• Use a continuity test from R7150 to U7000 (Pin 20).
• If there's a break, repair the PCB trace.

---

Step 3: Battery Low Protection (PM_BATLOW_L)

Test: Verify Battery Low Logic


Test Points:

• PM_BATLOW_L (Battery Low Protection)
• R5380 (10KΩ Pull-Up Resistor to 3.42V)

Perform Test:

• Measure PM_BATLOW_L voltage when the battery is fully discharged.
  • Expected: 3.3V when battery is OK.
  • Abnormal: 0V → Battery stays in deep discharge mode.

If PM_BATLOW_L Stuck LOW (0V):
Inject 3.3V Manually (Force Charging Test):

• Temporarily apply 3.3V to PM_BATLOW_L using a power supply.
• If charging starts, SMC is not properly releasing battery low protection.

Check R5380 (10KΩ Pull-Up Resistor):

• If open, replace it and retest.

Reflash SMC Firmware:

• If issue persists, SMC may have corrupted firmware causing it to ignore battery wake-up.

---

Step 4: U7000 Debugging (Charging Enable Logic)

Test: Force-Activate Battery Charging


Test Points:

• BATDRV (Pin 20 on U7000)
• CHGR_ACOK (Pin 17 on U7000)
• ACOK (Pin 5 on U7000)
• PPBUS_G3H (Pin 27 on U7000 - Main Power Rail, 12.56V)

Perform Test:

• Measure BATDRV voltage with the charger connected:
  • Expected: 12.6V when charging.
  • If 0V, U7000 is not enabling battery charge.

If BATDRV is 0V (No Charge Enabled):
Force Inject 12.6V to BATDRV:

• Temporarily apply 12.6V to BATDRV using a power supply.
• If battery starts charging, U7000 is not switching properly → Replace U7000.

Measure CHGR_ACOK (Pin 17 on U7000):

• Expected: 3.42V when charger is valid.
• If 0V, U7000 is not detecting charger correctly.

Measure ACOK (Pin 5 on U7000):

• Expected: 3.42V when MagSafe is connected.
• If 0V, check C7012, R7011, and R7012 (voltage divider resistors).

---

Advanced Debugging Summary & Next Steps

Battery I²C (SMBus Analysis)	SMBUS_SMC_5_G3_SCL, SMBUS_SMC_5_G3_SDA	100kHz square wave	Check R5421, R5422 pull-ups, try wake-up test
Battery Current Monitoring (CHGR_BMON)	CHGR_BMON (Pin 20 U7000)	0.8V - 1.2V	Check R7150 (shunt resistor)
Battery Low Protection (PM_BATLOW_L)	PM_BATLOW_L, R5380	3.3V (normal)	If 0V, force HIGH or reflash SMC
Battery Enable (BATDRV - U7000 Pin 20)	BATDRV (Pin 20 U7000)	12.6V if charging	If 0V, force HIGH, replace U7000

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Final Advanced Action Plan


Probe SMBus (SCL/SDA) with an oscilloscope. If inactive, check pull-ups & try forcing 3.3V on SDA.
Measure CHGR_BMON. If 0V, check R7150 shunt resistor.
Check PM_BATLOW_L. If LOW, force it HIGH (3.3V) and see if charging starts.
Manually inject 12.6V into BATDRV to test U7000 response.
If everything else fails, reflash SMC firmware.

Capture the data, and report back with the results. We can isolate the failure down to the exact component!

[Sancho Marcelino]

Correction:
R5380 is NOT 10KΩ – It is 2.0KΩ (confirmed from the schematic).

The overall test method is still valid, but the resistor value must be corrected to 2KΩ instead of 10KΩ to match the real circuit design.

[dclass-pro]

Hi Sancho Marcelino,
thanks for the guide but by doing all the tests I checked:
Where on the 2 pins of the battery data exchange (Present)
the battery is charging correctly in fact the power supply starts to absorb about 2A.
If I disconnect and reconnect the battery the macbook starts and works and sees the battery charged with the percentage.
If I put the mac on charge during use, the battery charge increases and works well.
the problem is present only and only if the battery discharges to 0 and I put it on charge, the power supply charges it because the absorption increases to 2a but the mac does not turn on until I disconnect the battery and reconnect it.