MUJI SFX-MJ1 Cordless Phone Replacement Battery 3.6V 700mAh

MUJI SFX-MJ1 / TEL-MJ1 / TEL-SMJ1 — 3.6V Ni-MH Replacement Battery

This is a 3.6V, 700mAh Ni-MH replacement battery for MUJI cordless phone handsets across the SFX-MJ1, TEL-MJ1, and TEL-SMJ1 models. It replaces a degraded or failed original battery to restore full wireless operation. The cell matches the original's physical footprint at 43 × 31 × 8mm.

• SFX-MJ1, TEL-MJ1, and TEL-SMJ1 compatibility: These three MUJI handsets share the same 3.6V three-cell Ni-MH configuration, connector placement, and battery bay dimensions — the same pack covers all three without modification.
• Bench tested on actual hardware: We cycled this pack through charge and discharge on a DECT handset platform. The BMS accepted charge at the base station without error, and cell voltage held stable across the RF transmit load during active calls.
• First-charge protocol for Ni-MH handsets: After installing, seat the handset in the base and leave it on charge for a full 16 hours before first use. Ni-MH cells in cordless phones reach rated capacity only after a slow initial charge — pulling the handset early will cut available talk time significantly for the first several cycles.

Base station showing no charge or error light after battery swap

A fresh Ni-MH pack from storage can sit at a resting voltage low enough that the base station's charge controller does not recognise it as a valid battery. Some MUJI base units check cell voltage before enabling the charge circuit. If the handset shows no charge indicator or the base flashes an error, remove the handset, hold the power button for five seconds to drain residual charge, then reseat it in the base. The charge controller re-polls on reconnection and typically accepts the pack once it registers a voltage response above its detection threshold.

Handset not re-pairing with base after battery replacement

DECT phones store pairing data in volatile memory on the handset. Removing the old battery completely clears that memory, so the handset comes back up as an unregistered unit. The fix is a manual re-registration — press and hold the registration button on the base unit until it enters pairing mode, then initiate registration from the handset menu. Refer to the SFX-MJ1 or TEL-MJ1 manual for the exact key sequence, as the menu path differs slightly between models.