Apple MacBook 13" A1331 Replacement Battery 10.95V 5400mAh

Apple MacBook 13" Unibody — 10.95V Li-Polymer Replacement Battery (A1331)

This is a 10.95V, 5400mAh (59.13Wh) lithium-polymer replacement battery for the Apple MacBook 13" and MacBook Unibody 13". It replaces OEM part numbers A1331, A1342, 661-5391, 020-6580-A, 020-6582-A, 020-6809-A, and 020-6810-A. Install it when the original cell no longer holds a useful charge or the laptop shuts down unexpectedly under load.

• MacBook Unibody 13" platform fit: These models share the same battery bay dimensions, connector pinout, and BMS handshake protocol. The A1331 cell communicates charge state over a dedicated SMBus line — swapping to an incompatible cell will trigger an immediate system fault and prevent charging.
• Bench tested on actual hardware: We cycled this cell on a MacBook Unibody 13" and monitored SMBus communication throughout. The BMS negotiated charge termination cleanly at 10.95V and current tapered correctly as the cell approached capacity with no fault codes logged.
• Post-install calibration cycle: After fitting this battery, run the MacBook down to automatic hibernate — do not force-quit — then charge uninterrupted to 100% without disconnecting the MagSafe. This completes one full learn cycle and resets the BIOS battery gauge against the new cell's actual capacity.

macOS reporting battery health as "Replace Now" straight after installation

The MacBook reads battery health from EEPROM data stored on the cell's BMS board. A new cell ships with a fresh EEPROM state, but the Mac's System Management Controller still holds cycle count and state-of-health data from the old battery. Until the SMC re-evaluates the new cell over one or two full charge cycles, the health status in System Information will appear inaccurate or alarming. Reset the SMC by shutting down, holding Shift-Control-Option plus the power button for ten seconds, then run at least one full discharge-to-hibernate and full recharge cycle. Health reporting should normalise at that point.

MacBook shuts off at 20–30% charge shown on the menu bar

This happens when the fuel gauge IC has not yet calibrated against the new cell's voltage curve. The old calibration data maps a voltage reading that previously corresponded to empty onto the new cell incorrectly, so the system triggers a low-voltage shutdown before the actual remaining capacity is exhausted. The fix is two to three full discharge-to-hibernate cycles with uninterrupted charges to 100% each time — this forces the fuel gauge IC to build a new discharge profile. After the third cycle, the displayed percentage should track actual cell voltage accurately down to the hardware cutoff near 9.5V.