Nokia 6340 BLB-3 Replacement Battery 3.7V 900mAh

Nokia 6340 / 8260 / 8290 Series — 3.7V Li-ion Replacement Battery (BLB-3)

This is a 3.7V 900mAh Li-ion replacement for the Nokia BLB-3 cell. It fits the Nokia 6340, 6340i, 8260, 8290, and several other models that share the same form factor and connector. Dimensions are 52.89 × 33.28 × 7.33mm — a direct physical match to the original cell bay.

• 6340, 8260, 8290 platform compatibility: These models share the BLB-3 footprint, voltage rail, and contact layout. The same connector orientation and BMS communication protocol runs across all of them, so one cell covers the group without modification.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a Nokia 8260. The BMS accepted the charge handshake on the first cycle, protection thresholds triggered correctly at the expected voltage floor, and the fuel gauge IC began tracking within the first full discharge.
• Fuel gauge recalibration on first use: After installation, run one complete discharge down to automatic shutoff, then charge uninterrupted to 100% before enabling any fast-charge mode. This gives the fuel gauge IC a clean reference curve against the new cell — skipping this step is the main cause of erratic percentage readings on Nokia devices.

Why the Nokia 6340 reports wrong battery percentage after a cell swap

Nokia's fuel gauge IC builds its capacity model from the discharge history of the cell it first calibrated against. When you swap in a new cell, that stored model no longer matches the actual discharge curve. The gauge reads against the old curve, so the percentage it displays drifts from the true state of charge. One full discharge-charge cycle overwrites the reference data and brings the display back into alignment with the new cell.

Sudden shutdown at 20–30% on the replacement cell

This is a voltage cliff issue, not a capacity problem. Under load — an active call, backlight at full, or network search — the cell voltage drops faster than the fuel gauge expects. When the cell voltage hits the BMS cutoff threshold, the phone shuts off even though the displayed percentage still looks safe. The fix is completing that first full calibration cycle so the gauge IC maps the actual voltage-to-capacity curve of the new cell. After one proper cycle, the shutdown point and the displayed percentage track together at roughly 3.4–3.5V under load.