Nokia BL-4C Replacement Battery 3.7V 550mAh

Nokia 107 / 108 Series — 3.7V Li-ion Replacement Battery (BL-4C)

This is a 3.7V, 550mAh Li-ion cell built to the BL-4C form factor. It fits the Nokia 107, 108, 1265, 1325, and 34 additional Nokia models that share the same battery bay and connector. Dimensions are 53.00 × 34.00 × 4.80mm — a direct physical match to the original cell.

• Multi-model Nokia compatibility: The 107, 108, 1265, and 1325 all run from the same 3.7V rail and use an identical 3-pin connector with the same BMS handshake protocol. One cell fits all of them without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on a Nokia 107 unit. The BMS accepted the charge curve without fault flags, and the protection circuit tripped correctly at the low-voltage cutoff threshold during deep discharge testing.
• Fuel gauge recalibration on first install: After fitting this cell, run one full discharge to auto-shutoff, then charge uninterrupted to 100% before normal use. The Nokia 107's fuel gauge IC was calibrated to the old cell's discharge curve — one complete cycle resets it to the new cell's actual capacity.

Sudden shutdown at 20–30% on the Nokia 107 after a cell swap

The Nokia 107 uses a basic coulomb counter that tracks charge in and out of the cell. When you fit a new cell, that counter has no valid reference for the new cell's voltage-to-capacity curve. Under even modest load — a call, an SMS burst — the cell voltage drops below the phone's cutoff threshold before the displayed percentage reaches zero. The phone shuts off not because the battery is defective, but because the fuel gauge IC is reading from stale calibration data. One full discharge-to-shutoff followed by a complete charge cycle resets the reference curve and eliminates the early cutoff.

Nokia 107 not powering on after the replacement cell sat in storage

Li-ion cells in storage self-discharge over time. If the BL-4C cell drops below approximately 2.5V per cell, the BMS triggers a lockout to prevent damage — and the phone will not respond to the power button or show any charging indicator. Connect the phone to a charger and leave it for 15–20 minutes without pressing anything. The charge IC will trickle current into the cell at a reduced rate until voltage climbs above the BMS re-enable threshold, typically around 2.9V, after which normal charging resumes and the phone will power on.