About this replacement
Apple Magic Mouse 2 A1657 / A1672 — 3.7V Li-ion Replacement Battery (020-00633)
This 3.7V 1850mAh Li-ion battery replaces the internal rechargeable cell in the Apple Magic Mouse 2. It fits models A1657 and A1672 — both share the same battery footprint and connector. Dimensions are 51.50 × 33.80 × 10.20mm, matching the original cell's slot exactly.
- A1657 and A1672 compatibility: Both Magic Mouse 2 revisions use the same 3.7V Li-ion cell with the same BMS communication protocol. Voltage rail and connector are identical across both model numbers, so one battery fits both without modification.
- Bench tested on actual hardware: We ran this cell in a Magic Mouse 2 A1657 unit. The BMS handshake completed on first connection, macOS reported battery percentage correctly in the menu bar, and charge acceptance from the Lightning port was normal with no error state triggered.
- Lightning port orientation during charging: The Magic Mouse 2 charges through a port on its underside, making it unusable while plugged in. Charge the mouse fully before a session rather than mid-use — connecting the cable during active work flips the mouse upside down and cuts off tracking entirely.
Why the Magic Mouse 2 stops reconnecting after a battery swap
When the internal cell is fully depleted before replacement, the mouse loses its stored Bluetooth pairing state. The BMS cuts power completely at low voltage to protect the cell, and the onboard memory loses context. After fitting a new battery, the mouse may not automatically reconnect to the paired Mac. Hold the power switch on the underside for three seconds, then toggle Bluetooth off and on in macOS System Settings to force a reconnection without a full re-pair.
Mouse pointer stuttering or skipping as battery voltage drops
The Magic Mouse 2 reduces its Bluetooth polling rate when cell voltage falls below approximately 3.5V. This is normal end-of-life behaviour — the firmware throttles radio activity to stretch remaining charge. The result is visible as intermittent pointer lag or short freezes that worsen progressively. If stuttering persists after fitting a new battery, check macOS System Settings → Battery and confirm the mouse is showing above 20% before dismissing a fault in the new cell.