Doro Primo 368 Replacement Battery RCBNTC05 3.7V 1000mAh

Doro Primo 368 — 3.7V Li-ion Replacement Battery (RCBNTC05)

This is a 3.7V, 1000mAh Li-ion replacement battery for the Doro Primo 368 mobile phone. It replaces part number RCBNTC05 and restores power to a phone that no longer holds a charge or fails to turn on. Dimensions are 62.15 x 38.10 x 4.60mm — confirm these against your original cell before installing.

• Primo 368 fitment: The Primo 368 uses a removable cell behind the rear cover. This battery matches the original voltage rail, connector position, and BMS handshake so the phone's charge IC accepts the cell without errors.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on a Primo 368 unit. The BMS negotiated correctly with the charge IC on the first cycle, with no overcharge or thermal cutoff events recorded.
• Fuel gauge recalibration on first use: On first use after installation, disable any fast-charge mode for one full discharge-charge cycle. This allows the fuel gauge IC to build an accurate discharge curve against the new cell before high-current charging is applied to an uncalibrated system.

Sudden shutdown at 20–30% on the Primo 368 after a cell swap

This happens because the fuel gauge IC is still using the discharge curve of the old, degraded cell. The new cell has a different voltage-to-capacity profile, so the IC misreads the state of charge. When load spikes — a call, screen brightness surge, or network scan — the actual cell voltage drops below the shutdown threshold before the gauge reaches zero. One full discharge-charge cycle without interruption resets the coulomb counter and corrects the reported percentage.

Phone won't power on after the replacement battery was left uncharged in storage

Li-ion cells self-discharge in storage. If the cell voltage drops below approximately 2.5V, the BMS enters a lockout state to prevent damage and the phone will not respond to the power button. Connect the phone to a wall charger — not a USB port — and leave it for 15–20 minutes without pressing anything. The charge IC will trickle-charge the cell back above the BMS recovery threshold, after which normal charging resumes.