Emporia Telme C120 Replacement Battery 3.7V 1050mAh

Emporia Telme C120 / C121 — 3.7V Li-ion Replacement Battery (BAT-C120)

This is a 3.7V 1050mAh Li-ion cell that fits the Emporia Telme C120 and Telme C121. Both models share the same battery bay dimensions (53.00 × 33.90 × 5.60mm), connector pinout, and BMS handshake, so one part number covers both. Capacity is 1050mAh (3.89Wh), matching the original Emporia BAT-C120 specification.

• C120 and C121 shared platform: Both handsets run the same voltage rail, use the same physical connector, and present identical BMS communication requirements. Emporia carried the battery design across both models unchanged, which is why a single BAT-C120 cell works in either device without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge under standard GSM standby and call load conditions. The BMS accepted charge handshake on first connection and held voltage within spec across the full discharge curve without tripping protection cutoff.
• Fuel gauge recalibration on first use: On first use after installation, run one complete discharge-charge cycle with fast charging disabled if your charger supports it. This gives the fuel gauge IC a clean reference curve against the new cell before any high-current charging pushes current into an uncalibrated state.

Sudden shutdown at 20–30% on the Telme C120 after a cell swap

The Telme C120 fuel gauge IC calibrates its percentage readout against the discharge curve of the original cell. A new cell has a slightly different impedance profile, so the IC misreads remaining charge and triggers shutdown before the display reaches zero. This is not a faulty battery — it is the fuel gauge losing track of the actual voltage floor. One full discharge to automatic shutoff followed by a complete charge resets the coulomb counter and re-anchors the percentage readout to the new cell curve. After that cycle, shutdowns at 20–30% should not recur.

Phone not powering on after the replacement battery sat in storage

Li-ion cells shipped or stored without a charge can drop below 2.5V per cell, which triggers BMS lockout to prevent damage. The Telme C120 will show no sign of life — no boot screen, no charging indicator — when the cell is in this state. Connect to a wall charger rather than a USB port on a PC, as wall adapters supply enough current to wake the BMS out of deep-discharge protection. Leave it connected for at least 15–20 minutes before attempting to power on; once the cell climbs above 3.0V, the BMS releases the lockout and normal charging resumes.