About this replacement
Apple Magic Keyboard (A1645) — 3.76V Li-Polymer Replacement Battery
This 3.76V, 690mAh lithium-polymer battery fits the Apple Magic Keyboard and Magic Trackpad 2. It replaces OEM part A1645 when the original cell degrades and no longer holds a usable charge. Slim at 2.00mm thick, it fits the tightly packaged internal cavity without modification.
- Magic Keyboard and Magic Trackpad 2 compatibility: Both devices share the A1645 cell format — same voltage rail, same connector pinout, same BMS handshake protocol. One part covers both peripherals in your setup.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a Magic Keyboard unit. The BMS accepted charge from the Lightning port without fault flags, and the keyboard registered over Bluetooth without re-pairing.
- Lightning port charging tip: The Magic Keyboard charges through its Lightning port while in use — but only when the port cover is open and the cable is seated fully. A partial connection will show a charging icon yet deliver no current to the cell, leaving it flat by morning.
Keyboard pairing lost after battery replacement
Replacing the A1645 cell causes a full power interruption. Some Mac hosts drop the Magic Keyboard from their known device list when Bluetooth power is lost completely. The keyboard does not always re-pair automatically on first power-up. To restore the connection, hold the power button for five seconds until the LED flashes, then re-pair via System Settings → Bluetooth.
New battery showing low charge warning immediately after install
Li-polymer cells ship at a partial state of charge — typically 30–50% — for transport safety compliance. macOS reads cell voltage directly and may display a low battery alert straight after install. Connect the Lightning cable and charge to 4.2V (full) before drawing conclusions about cell health. The alert clears once the BMS reports a full charge cycle complete.