About this replacement
Sanyo SCP-8100 / MM-8100 — 3.7V Li-ion Replacement Battery
This 3.7V 950mAh Li-ion cell is a direct swap for the original battery in the Sanyo SCP-8100 and MM-8100 flip phones. Both models share the same battery bay geometry and connector orientation. Capacity is 950mAh (3.52Wh), matching the factory specification.
- SCP-8100 and MM-8100 compatibility: These two models use the same battery housing, contact pad layout, and charge IC handshake — one cell fits both without modification or adapter.
- Bench tested on actual hardware: We cycled this cell through full charge and discharge on the SCP-8100 platform. The BMS accepted charge current correctly, balanced to 4.2V at termination, and showed no false cutoff on discharge.
- Fuel gauge recalibration on first cycle: After fitting this cell, run one complete discharge down to auto-shutoff, then charge uninterrupted to 100%. The SCP-8100's fuel gauge IC maps its percentage curve to the old cell — one full cycle resets that mapping against the new cell's actual discharge profile.
Why the SCP-8100 reports wrong battery percentage after a cell swap
The SCP-8100 uses a fuel gauge IC that builds its percentage model from the previous cell's discharge curve over many cycles. When a new cell goes in, the IC still references the old curve — which means percentage readings can read high or low by a wide margin. This is not a fault in the replacement cell. One complete discharge-to-shutoff followed by a full charge gives the IC enough data to recalibrate. After that cycle, percentage accuracy returns to normal.
Sudden shutdown at 20–30% on the replacement cell
This happens when the cell voltage drops below the load threshold before the displayed percentage reaches zero. On a mid-2000s flip phone, the backlight and RF transmit load can pull the cell below 3.2V faster than the fuel gauge tracks it. The BMS trips a hard cutoff to protect the cell — the phone shuts off even though the gauge still shows charge remaining. If this occurs repeatedly after one recalibration cycle, check that the battery contacts in the bay are clean and making full contact — a high-resistance connection causes a steeper voltage drop under load.