MacBook no longer charges
the battery

Isolate the failure point

MacBook charging failures split into three distinct failure paths: charger/USB-C port issue, charging circuit failure (SMC/PMU/PMIC), or battery connector/cell failure. Correctly identifying which path saves diagnosis time.

Start with bench testing the power adapter. Use a multimeter to measure DC output at the USB-C connector. Most MacBook chargers output 14.5V–20.2V depending on model. If voltage is absent or significantly lower than spec, the charger is faulty—replace and test again.

If charger output is correct, connect it to the MacBook while the machine is off. Measure voltage on the USB-C power rail inside the device. Test points vary by model, but typically PPBUS_G3H (main bus) should read 16.5V–20V when a valid charger is connected. If rail voltage is missing or drops below 3.3V, the charging circuit has failed.

Confirm the charger output

MacBook chargers are PFC (power factor correction) switched-mode supplies. Use a bench supply or calibrated multimeter set to DC voltage mode.

Chargers fail most commonly at the primary-side power MOSFET or the feedback control IC. On Apple's newer chargers, the controller is typically SyV83201A or equivalent. If output voltage is missing entirely, measure 5V standby on the secondary side. No standby voltage indicates an open transformer primary or dead front-end rectifier.

Test the power management IC

Once charger output is confirmed good, the PMIC (Power Management IC) is the next suspect. On modern MacBooks, charging is orchestrated by the ISL6259 or TPS51125 series buck regulator, paired with a charging control IC like LP8550 or proprietary Apple SMC firmware.

Measure the input voltage to the PMIC with the charger connected. This is typically the PPBUS_G3H or VBUS rail. Should be within 16.5V–20V. Next, measure the PMIC's output rail—usually PP5V0_S0 or similar. Expected range: 4.8V–5.2V. If input is present but output is 0V, the PMIC's enable pin (PGOOD, EN) is held low or the IC itself is shorted.

Check for DC bias on the PMIC enable and feedback pins. Typical enable voltage for a healthy IC: 1.8V–3.3V. If stuck at ground, check for a short on the supply rail or a failed decoupling capacitor.

Measure ESR (Equivalent Series Resistance) on bulk capacitors feeding the PMIC input. Use an ESR meter if available. Capacitors with ESR > 500 mΩ fail the charging loop stability and must be replaced. Aged tantalum capacitors in pre-2019 MacBooks frequently show this failure.

Trace the battery charging path

If the PMIC rails are alive and stable, measure continuity on the battery charging connector. Disconnect the battery first—this prevents parasitic paths that mask open connections. Measure resistance between the main charge sense pin and ground. Should be < 1 Ω. Resistance > 10 Ω indicates oxidation or a cracked trace.

Battery connector failures are mechanical: corrosion from humidity, repeated mating/unmating wear, or thermal cycling solder cracking. Clean the connector pads with isopropyl alcohol (90%+ purity) and inspect under magnification for green oxidation. If present, use a brass wire brush to gently scrub the pins and solder pad surface.

Measure DC voltage directly across the battery cell terminals with the charger connected and SMC/firmware enabled. A healthy charging algorithm delivers 8.0V–8.4V on a 2S (two-cell series) battery, ramping up from 0.1A to 2.5A as bulk charge progresses. If cell voltage remains at 0V or the voltage climbs above 8.5V, the battery protection circuit (BMS) inside the battery pack has faulted or the charging IC is not communicating with the SMC.

If all power rail voltages are correct but the battery remains uncharged, the fault is inside the battery pack: open cell connection, faulty BMS IC, or aged cells that cannot accept charge. Battery packs cannot be field-repaired; they must be replaced as an assembly.

Diagnostic decision tree

1. Charger produces correct DC voltage (14.5V–20V)? If NO: Charger is faulty, replace.
2. PPBUS_G3H rail measures 16.5V–20V with charger connected? If NO: Check USB-C connector for corrosion, measure continuity on power traces (0.1–0.5 Ω expected). If traces fail, micro-welding repair required.
3. PMIC output (5V rail) is stable? If NO: Measure PMIC enable pin. If stuck low, check for shorted capacitor on enable net. If output shorted, PMIC IC is likely open or has a gate-drive failure.
4. Battery connector shows <1 Ω continuity? If NO: Clean connector, inspect for corrosion. If corrosion is deep, reflow the connector pads.
5. i2c clock/data lines toggle? If NO: SMC communication is dead. Reflash SMC firmware or replace the SMC IC if shorted.
6. All voltages correct but battery remains at 0V charge? Battery pack internal BMS has failed, replace battery.