Nokia BL-4C 2650 Replacement Battery 3.7V 900mAh

Nokia 2650 / 2651 / 2652 / 3108 — 3.7V Li-ion Replacement Battery (BL-4C)

This is a 3.7V, 900mAh Li-ion replacement battery for the Nokia BL-4C platform. It fits the Nokia 2650, 2651, 2652, and 3108, along with over 30 additional Nokia handsets that share the same BL-4C cell format. Capacity figure is taken directly from the product specification — 900mAh / 3.33Wh.

• BL-4C platform compatibility: These models share the same contact pitch, physical footprint, and BMS handshake requirements. The BL-4C cell format was Nokia's standardised mid-range battery across several product lines released in the 2000s, so a single cell revision covers all of them without modification.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a BL-4C compatible handset. The BMS accepted charge current without fault, contact resistance stayed within range, and the fuel gauge IC responded correctly after one full discharge-charge cycle.
• Fuel gauge recalibration on first use: After installing this cell, run one complete discharge down to automatic shutoff, then charge uninterrupted to 100%. The phone's fuel gauge IC is calibrated against the old cell's discharge curve — skipping this step causes the percentage readout to jump or report incorrectly until it recalibrates.

Why the Nokia 2650 shuts down suddenly at 20–30% battery remaining

This is a voltage cliff failure, not a capacity problem. When the cell ages, its internal resistance rises. Under load — a call connecting, backlight at full brightness — the terminal voltage drops faster than the fuel gauge expects and hits the BMS cutoff threshold before the displayed percentage reaches zero. The phone reads 25% but the cell cannot hold voltage under that brief current surge. Replacing the cell eliminates the resistance spike, but the gauge will still report the wrong percentage until recalibrated with one full discharge-charge cycle.

Phone does not power on after sitting in a drawer for months

Li-ion cells that self-discharge below approximately 2.5V per cell trigger a BMS lockout to prevent reverse-polarity damage. The phone will show nothing on screen — no Nokia logo, no charging indicator — even with a charger connected. Connect the phone to a low-current charger and leave it for 20–30 minutes before attempting to power on. If the BMS accepts a trickle recovery current, the cell will rise above the lockout threshold and normal charging will resume. If the cell has been below 2.5V for an extended period, recovery may not be possible and the cell should be replaced.