About this replacement
Sanyo SCP-8100 / MM-8100 — 3.7V Li-ion Replacement Battery
This 3.7V 1500mAh Li-ion cell replaces the original battery in the Sanyo SCP-8100 and MM-8100 mid-2000s smartphones. It slots into the same battery bay and connects via the original terminal contacts. If your original cell no longer holds charge or the phone shuts down unexpectedly, this is the direct swap.
- SCP-8100 and MM-8100 compatibility: Both models share the same battery bay dimensions, terminal layout, and 3.7V nominal voltage rail. The same cell fits either handset without modification to the contacts or housing.
- Bench tested on actual hardware: We ran full charge and discharge cycles on this cell and confirmed the BMS holds the cutoff voltage correctly at both ends — no premature shutoff at the top of charge, no hard cutout from over-discharge protection triggering too early.
- Fuel gauge recalibration on first use: On first installation, run one complete discharge down to automatic shutoff, then charge uninterrupted to 100% before normal use. The SCP-8100's fuel gauge IC was calibrated to the original cell's discharge curve — one full cycle resets it against the new cell so percentage readings stay accurate.
Why the SCP-8100 reports wrong battery percentage after a cell swap
The SCP-8100 uses a fuel gauge IC that tracks charge by measuring voltage curves against a stored discharge profile from the original cell. A new cell has a slightly different internal resistance and discharge curve, so the IC's stored model no longer matches what it's measuring. This shows up as the percentage jumping around or the phone reporting 40% right before it shuts down. One full discharge-to-shutoff followed by a complete uninterrupted charge forces the IC to relearn the curve against the new cell's actual behaviour.
Phone shuts off suddenly at 20–30% on the replacement cell
This is a voltage cliff issue, not a capacity problem. When the cell voltage drops below approximately 3.5V under load — during a call, screen-on use, or any modem activity — the phone's protection circuit cuts power before the fuel gauge registers empty. The SCP-8100's modem and display draw enough current to cause a sharp voltage sag on a cell the gauge hasn't calibrated to yet. Run the recalibration cycle first: discharge fully to automatic shutoff, charge to 100% without interruption, and the shutoff threshold should stabilise at or below 10%.