Sanyo SCP-7400 Replacement Battery 3.7V 1600mAh Li-ion

Sanyo SCP-7400 / MM-7400 — 3.7V Li-ion Replacement Battery (SCP-13LBPS)

This is a 3.7V, 1600mAh Li-ion battery for the Sanyo SCP-7400 and MM-7400 candybar-style phones. It replaces OEM part numbers SCP-13LBPS and CSYO7400LIO. If your phone no longer holds a charge or shuts off unexpectedly, this cell restores full operating voltage to the device.

• SCP-7400 and MM-7400 compatibility: Both models share the same battery bay dimensions, connector pinout, and 3.7V nominal voltage rail. One cell fits all variants listed — SCP7400, MM7400, and MM-7400 — because the housing and BMS handshake are identical across the range.
• Bench tested on actual hardware: We cycled this cell through charge and load on the SCP-7400 platform. The BMS held cutoff at the correct thresholds, charge acceptance was normal from 0%, and the protection circuit tripped cleanly at the expected over-discharge floor.
• Fuel gauge recalibration on first use: After fitting this cell, disable any fast-charge accessory for the first full discharge-to-charge cycle. The phone's fuel gauge IC is calibrated to the old cell's discharge curve. One uninterrupted cycle at standard current lets it relearn the new cell before high-current charging begins.

Why the SCP-7400 reports wrong battery percentage after a cell swap

The SCP-7400 uses a fuel gauge IC that tracks charge state by measuring voltage against a stored discharge curve from the original cell. A new cell has a different internal impedance profile, so the IC maps voltage to percentage incorrectly at first. The phone may show 80% when the actual state of charge is closer to 50%, or jump erratically between readings. One full discharge down to automatic shutoff, followed by an uninterrupted charge to 100%, resets the coulomb counter against the new cell's actual curve.

Sudden shutdown at 20–30% on the replacement cell

This happens when the cell voltage drops sharply under load — the screen backlight and RF transmitter together pull enough current to cause a voltage cliff the fuel gauge did not predict. The phone reads 25% but the cell is already below the BMS cutoff threshold under that combined load. It is not a faulty battery; it is the IC still using the old cell's voltage-to-capacity map. After the first full calibration cycle, the percentage at shutdown should align to below 5% at a resting cell voltage of approximately 3.5V.