SP-A5 Мегафон Replacement Battery 3.7V 1300mAh Li-ion

Mегафон SP-A5 — 3.7V Li-ion Replacement Battery

This is a 3.7V 1300mAh Li-ion battery for the Mегафон SP-A5 smartphone. It slots in as a direct cell replacement when the original has degraded through repeated charge cycles. Dimensions are 43.50 × 47.00 × 6.10mm — confirm these against your existing cell before ordering.

• SP-A5 platform fit: The SP-A5 runs a single-cell 3.7V architecture with a fixed connector layout. This cell matches that voltage rail and physical footprint, so the charge IC on the board sees the correct cell characteristics at startup.
• Bench tested on actual hardware: We cycled the cell through charge and discharge on the bench. The BMS accepted the charge handshake without fault flags, and the protection circuit tripped correctly at the low-voltage cutoff threshold.
• Fuel gauge recalibration after installation: On first use, disable any fast-charging mode and run one full discharge-to-charge cycle at standard current. This lets the fuel gauge IC map its coulomb counter against the new cell's actual discharge curve before high-current charging begins.

Sudden shutdown at 20–30% on the SP-A5 after a cell swap

The SP-A5 fuel gauge IC holds a discharge curve calibrated to the old cell. A new cell with a different internal resistance profile will hit a voltage cliff under modem or screen load that the gauge did not predict. The phone reads 25% but the cell voltage collapses below the protection threshold under that instantaneous current draw. Run two full discharge-charge cycles at standard charge current — by the second cycle the coulomb counter has enough data to track the new cell accurately.

Phone shows wrong battery percentage after fitting the replacement

The fuel gauge IC on the SP-A5 stores a learned capacity value tied to the original cell's impedance and discharge slope. Swapping the cell does not reset that stored value automatically. The result is percentage readings that jump erratically or plateau for long stretches before dropping fast. Drain the phone fully until it shuts off, then charge uninterrupted to 100% — this forces the IC to rewrite its reference curve against the new cell.