About this replacement
Apple MacBook 13" A1278 — 10.8V Li-Polymer Replacement Battery (A1280)
This is a 10.8V, 4200mAh Li-Polymer replacement battery for the Apple MacBook 13" A1278, including the Aluminum Unibody 2008 version and MB466 variants. It replaces OEM part A1280 and fits the physical bay and connector without modification. Capacity is 45.36Wh, matching the original cell specification.
- A1278 and MB466 series fit: These models share the same 10.8V three-cell Li-Polymer configuration, identical connector pinout, and the same BMS communication protocol over the SMBus line — so one cell works across all listed variants without adapter or firmware conflict.
- Bench tested on actual hardware: We ran this cell on an A1278 board and confirmed the SMBus handshake completed, charge current accepted at the expected rate, and the BMS did not trigger a fault or refuse-to-charge condition during initial cycles.
- First-cycle discharge on the A1278: After installing, run the laptop on battery alone until it reaches hibernate-cutoff, then charge uninterrupted to 100%. This forces the MacBook's fuel gauge IC to relearn the new cell's actual capacity range and clears the inaccurate health warning that appears in System Information after every cell swap.
Why macOS shows a different Wh rating than the battery label after replacement
The Wh figure macOS displays in System Information is pulled from the EEPROM on the battery's BMS board, not measured in real time. OEM cells write their rated capacity into that register at the factory. Replacement cells may carry a different EEPROM value depending on the manufacturer, which causes macOS to show a Wh figure that doesn't match the label on the cell. This is a data mismatch, not a fault — the cell still charges and discharges at full capacity. After two to three full calibration cycles the fuel gauge IC will report a value closer to actual measured capacity.
MacBook A1278 shutting down at 20–30% charge shown on the menu bar
This happens when a cell — old or new — cannot hold voltage under combined CPU and display load as it approaches the lower end of its charge range. The fuel gauge IC estimates remaining charge based on voltage curves, but a voltage cliff under load causes the board to cut power before the displayed percentage reaches zero. It is not a fault in the replacement cell itself — it means the fuel gauge IC has not yet mapped the new cell's discharge curve. Run two full discharge-to-hibernate then charge-to-100% cycles; after that the shutdown threshold should track accurately above 5%.