MyPhone 6500 Replacement Battery MP-S-W 3.7V 850mAh

MyPhone 6500 — 3.7V Li-ion Replacement Battery (MP-S-W)

This is a 3.7V 850mAh lithium-ion cell built to fit the MyPhone 6500 smartphone. It replaces OEM part MP-S-W and restores power to the device when the original cell can no longer hold a usable charge. Dimensions are 62.44 × 38.95 × 4.40mm — confirm these against your existing cell before fitting.

• MyPhone 6500 fitment: The 6500 uses a compact form-factor cell with a low-current BMS tuned to the phone's standby and modem draw profile. This replacement matches the OEM connector pinout and voltage window, so the charge IC on the motherboard recognises the cell without requiring a firmware workaround.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the bench and monitored BMS response at the low-voltage cutoff threshold. The protection circuit tripped correctly at the expected floor, and the charge IC accepted a full charge cycle without flagging an error state.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging for one complete discharge-charge cycle. The fuel gauge IC on the 6500 is calibrated to the discharge curve of the original cell. Running one slow cycle against the new cell gives the IC enough data to reset its coulomb counter accurately.

Why the MyPhone 6500 reports wrong battery percentage after a cell swap

The 6500's fuel gauge IC tracks charge state using a coulomb counter that was trained on the original cell's internal resistance and discharge curve. When a new cell goes in, the counter still references the old profile, so percentage readings drift — often reading high early in discharge and then dropping sharply. This is not a fault in the replacement cell. One full slow discharge down to automatic cutoff, followed by a complete charge, gives the IC enough real data to rebuild its reference curve. After that cycle, percentage readout stabilises.

Sudden shutdown at 20–30% on the replacement cell

This happens when the modem or screen draws a current spike the cell cannot sustain at its present state of charge, and terminal voltage briefly drops below the BMS cutoff threshold — typically around 3.0V under load. The phone interprets that as a dead cell and shuts down, even though resting voltage may recover to 3.4–3.5V seconds later. A full slow conditioning cycle usually shifts this cutoff point because the fuel gauge recalibrates and the cell's internal resistance stabilises after a few charge-discharge passes. If shutdowns continue past cycle three, measure resting voltage after a full charge — it should read at or above 4.18V.