3.7V Sanyo PM8200 Replacement Battery 900mAh Li-ion

Sanyo PM8200 / SCP-8200 — 3.7V Li-ion Replacement Battery

This is a 3.7V 900mAh Li-ion replacement battery for the Sanyo PM8200 and SCP-8200 smartphones. It fits both the PM-8200 and SCP-8200 variants, which share the same battery bay and connector. Capacity is 900mAh (3.33Wh), matching the original cell specification.

• PM8200 and SCP-8200 compatibility: Both the PM8200 and SCP-8200 lines use the same 3.7V single-cell configuration and identical battery bay dimensions. The BMS handshake protocol is identical across these variants, so one cell works across the full model range without modification.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on the SCP-8200 platform. The BMS accepted the cell without fault codes, charge termination triggered correctly at 4.2V, and the protection circuit responded to a simulated short-circuit event within spec.
• Fuel gauge recalibration on first cycle: On first use after installation, disable fast charging and run one complete discharge down to automatic shutdown, then charge fully to 100%. This gives the fuel gauge IC a full sweep of the new cell's discharge curve before it locks in its reference points — skipping this step is the main reason the percentage readout drifts or jumps in the first few days.

Sudden shutdown at 20–30% on the PM8200 after a cell swap

This is a voltage cliff issue, not a capacity problem. The fuel gauge IC still holds the old cell's discharge curve in memory, so it reports 20–30% remaining at the exact moment the new cell's voltage drops below what the modem and display draw requires. The phone cuts power to protect itself even though the gauge hasn't reached zero. One full discharge-to-shutdown and full recharge cycle resets the coulomb counter and maps the new cell correctly — after that cycle, shutdowns at falsely high percentages stop.

OS reporting a wrong or jumping battery percentage after replacement

The fuel gauge IC on the PM8200 calibrates against a learned discharge curve stored from the original cell. When a new cell goes in, that stored curve no longer matches actual voltage-to-capacity behaviour, so the percentage reading skips or stalls. This is not a defective battery — it is an uncalibrated gauge. Run the phone from 100% down to automatic cutoff without interruption, then charge back to 100% without unplugging early. After that single uninterrupted cycle, the gauge IC locks onto the new curve and percentage reporting stabilises.