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

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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).

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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).

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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.