Simplehuman Mirror SH1S2P Replacement Battery 3.7V 5200mAh

Simplehuman Mirror SH1S2P — 3.7V Li-ion Replacement Battery (SH03)

This 3.7V 5200mAh Li-ion battery replaces the original SH03 cell in the Simplehuman Mirror SH1S2P. It powers the mirror's sensor activation, touch controls, and LED lighting array. Swap it in when the original cell no longer holds charge after repeated cycles.

• SH1S2P compatibility: The SH1S2P runs a single-cell 3.7V architecture with a specific BMS handshake for the LED driver and proximity sensor. This cell matches that voltage rail and connector, so the mirror's control board recognises the battery and drives the LED string at full current from the first power-on.
• Bench tested on actual hardware: We ran this cell through the SH1S2P's charge and discharge cycle on the bench. The BMS accepted charge without a fault flag, the sensor activation responded normally, and the LED driver maintained stable constant-current output across the full discharge curve.
• First-use charging on the SH1S2P: Charge the mirror fully before the first use after installation. The LED driver in this mirror calibrates its constant-current output against the cell voltage on first use. A partially charged cell on first power-on can cause uneven brightness across the LED ring on that initial session.

Why the SH1S2P LEDs dim before the battery indicator shows low

The SH1S2P's LED driver operates in constant-current mode, but only down to a minimum input voltage threshold — typically around 3.4V for this class of driver. When the cell voltage sags below that threshold under load, the driver can no longer sustain full current, and the LEDs dim noticeably. The battery indicator circuit reads resting voltage, not load voltage, so it still shows partial charge while the LEDs are already pulling less light. This is a cell-condition issue: a degraded original battery sags harder under the LED load than a fresh cell at the same state of charge.

Mirror not charging via USB after battery replacement

The SH1S2P's charge circuit requires a stable 5V input to initiate charging — some lower-output USB adapters and multi-port hubs drop below 4.8V under load, which causes the charge controller to not start. If the mirror shows no charge activity after a battery swap, test with a single-port USB adapter rated at 5V/1A or higher. Also check the USB cable — a cable with high resistance will drop voltage before it reaches the mirror's charge port. Swap to a known-good cable and a dedicated wall adapter; charge should initiate within 30 seconds.