MyPhone 1230 Replacement Battery MP-Y-1 3.7V 700mAh

MyPhone 1230 — 3.7V Li-ion Replacement Battery (MP-Y-1)

This is a 3.7V, 700mAh Li-ion replacement battery for the MyPhone 1230 smartphone. It matches the OEM part number MP-Y-1 and fits the original battery bay without modification. Voltage and cell dimensions (46.63 × 33.76 × 4.57mm) match the factory specification.

• MyPhone 1230 fit: The 1230 uses a fixed voltage rail at 3.7V nominal with a connector and form factor locked to the MP-Y-1 spec. This cell matches that rail, the physical footprint, and the connector orientation — no adapter needed.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the 1230 platform. The BMS accepted the cell without error flags, and the charge IC engaged at the correct constant-current setpoint.
• First-cycle calibration on the 1230: 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 MyPhone 1230 reports wrong battery percentage after a cell swap

The 1230's fuel gauge IC stores a learned discharge curve from the original cell. When a new cell goes in, that stored curve no longer matches the new cell's actual voltage-to-capacity profile. The OS reads voltage from the gauge and maps it to a percentage using the old data — so the number on screen drifts from reality. One full discharge-to-cutoff followed by a full charge resets the coulomb counter and lets the IC rebuild the curve against the new cell.

Sudden shutdown at 20–30% on the replacement cell

This happens when the cell voltage drops below the modem or display load threshold faster than the fuel gauge predicts — a voltage cliff. The gauge still shows 20–30% but the cell can no longer sustain voltage under peak draw, so the phone shuts down to protect the BMS. It is most common in the first few cycles before the fuel gauge IC recalibrates. Run two full discharge-charge cycles without fast charging and the cutoff point will shift back toward the correct level — confirm the cell is holding above 3.5V under load after cycle two.