Tecno Spark 2 Replacement Battery BL-34BT 3.8V 3200mAh

Tecno Spark 2 (KA7 / KA7O) — 3.8V Li-Polymer Replacement Battery (BL-34BT)

This is a 3.8V, 3200mAh Li-Polymer replacement battery for the Tecno Spark 2 smartphone, covering KA7 and KA7O variants. It replaces OEM part number BL-34BT. Fit this when the original cell no longer holds a useful charge or the phone shuts down unpredictably under load.

• KA7 and KA7O compatibility: Both KA7 and KA7O variants use the same BL-34BT footprint — 87.70 × 64.70 × 3.60mm — with the same connector orientation and BMS handshake. No modification needed for either board revision.
• Bench tested on actual hardware: We ran this cell through full charge and load cycles on a KA7 board. The BMS accepted the connection without fault flags, charge current ramped correctly, and the protection circuit tripped at expected cutoff thresholds.
• Fuel gauge recalibration on first use: After fitting, disable fast charging and run one complete discharge-to-charge cycle at standard current. This forces the fuel gauge IC to map its coulomb counter against the new cell's actual discharge curve before any high-current session begins on an uncalibrated reference.

Why the Spark 2 reports wrong battery percentage after a cell swap

The Spark 2 uses a fuel gauge IC that builds its state-of-charge model from accumulated charge and discharge data on the original cell. When a new cell goes in, that learned curve no longer matches the new cell's actual voltage-to-capacity relationship. The IC keeps using its old reference, so the percentage shown on screen drifts from reality. One full discharge down to automatic cutoff, followed by a full charge at standard rate, resets the coulomb counter baseline against the new cell and brings the reported percentage back into alignment.

Sudden shutdown at 20–30% charge remaining on the replacement cell

This happens when the modem, display, or a background process pulls a current spike the new cell cannot sustain at that state of charge — the cell voltage drops below the BMS cutoff threshold and the phone powers off even though the fuel gauge still shows charge remaining. It is a voltage sag event, not a capacity defect. The fuel gauge IC has not yet mapped the new cell's voltage cliff, so it does not warn before shutdown. Complete two or three full discharge-charge cycles at standard rate and the gauge IC recalibrates to the correct cutoff point, typically resolving the early shutdown.