MegaFon SP-A10 Compatible Battery 3.7V 1500mAh Li-ion

MegaFon SP-A10 — 3.7V Li-ion Replacement Battery

This is a 3.7V, 1500mAh Li-ion battery for the MegaFon SP-A10 smartphone. It replaces the original cell when the phone no longer holds charge, shuts down unexpectedly, or fails to power on after a full charge cycle. Capacity is rated at 5.55Wh and the cell measures 64.60 × 43.95 × 5.10mm.

• SP-A10 fit: The SP-A10 uses a compact removable cell at 3.7V nominal. This replacement matches the original voltage rail and connector footprint so the phone's charge IC communicates with the new cell without modification.
• Bench tested on actual hardware: We cycled this cell through a full discharge and charge on the SP-A10 platform. The BMS accepted the cell without triggering overcurrent cutoff, and the charge IC reached termination at the expected voltage ceiling.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC recalibrate against the new cell's discharge curve before high-current charging pushes current into an uncalibrated cell.

Why the SP-A10 reports wrong battery percentage after a cell swap

The SP-A10's fuel gauge IC stores a learned discharge curve from the original cell. When a new cell goes in, the IC is still referencing that old curve, so percentage readings drift from the actual state of charge. The gauge may report 40% when the cell is near depletion, or show 100% shortly after plug-in. One full discharge-charge cycle — run with fast charging disabled — gives the coulomb counter enough data to rebuild an accurate curve against the new cell's actual capacity.

Sudden shutdown at 20–30% on the replacement cell

This happens when the modem or display draws a current spike the cell cannot sustain at that state of charge, causing voltage to dip below the BMS cutoff threshold momentarily. The phone shuts down even though the reported percentage still looks safe. It is a voltage-cliff symptom, not a capacity fault. Run one full slow-charge cycle and check whether shutdowns persist below 3.6V resting voltage — if they do, reseat the cell connector and confirm the contact is clean and flush.