Apple MacBook Air 13" A1405 Replacement Battery 7.3V 6700mAh

Apple MacBook Air 13" A1369 Mid-2011 — 7.3V Li-Polymer Replacement Battery (A1405)

This is a 7.3V, 6700mAh (48.91Wh) lithium-polymer battery for the Apple MacBook Air 13-inch A1369, covering the Mid-2011 Core i5 and Core i7 models including MC503 and MC504. It replaces OEM part numbers A1405, 020-7379-A, 661-6055, and 020-8142-A. If your original cell no longer holds a charge or macOS flags battery health as degraded, this cell is the direct swap.

• A1369 platform fitment: All Mid-2011 MacBook Air 13-inch units share the same logic board voltage rail, ZIF connector, and BMS handshake protocol — that is why MC503, MC504, Core i5, and Core i7 variants all use the same A1405 cell pack.
• Bench tested on actual hardware: We ran this cell through a full charge cycle on an A1369 logic board. The BMS communicated correctly with the SMC, charge termination triggered at the expected threshold, and no fault codes were logged in the system controller.
• Post-install calibration on A1369: After fitting, run the battery down until the laptop hibernates on its own, then charge uninterrupted to 100% without interruption. This forces the SMC to relearn the new cell's capacity curve and clears the inaccurate health warning macOS posts after any cell swap.

Why macOS reports "Service Battery" immediately after fitting a new A1405

The MacBook Air's System Management Controller stores cycle count and capacity data from the old cell in EEPROM. When a new cell installs, the SMC reads stale EEPROM values and flags a health mismatch before the new cell has run a single cycle. This is not a fault with the replacement cell — it is a firmware state issue. Running one full discharge-to-hibernate then a full uninterrupted charge resets the learn cycle and clears the warning in most cases.

MacBook Air shutting down at 20–30% charge shown on the menu bar

This happens when the fuel gauge IC's stored charge map no longer matches the new cell's actual voltage curve. Under combined CPU and display load, the cell voltage drops faster than the old map predicts, and the SMC triggers an emergency shutdown before the displayed percentage reaches zero. The fix is calibration: fully discharge to automatic hibernate, then charge straight to 100% without unplugging. After two to three of these full cycles, the fuel gauge IC recalibrates against the new cell and the shutdowns stop. Target a resting open-circuit voltage of 8.2–8.4V at full charge to confirm the cell is seated correctly.