SH-01A Sharp SH905i Smartphone Replacement Battery 3.7V 700mAh

Sharp SH905i / SH906i Series — 3.7V Li-ion Replacement Battery (SH-01A)

This is a 3.7V, 700mAh Li-ion cell that replaces the original battery in the Sharp SH905i and SH906i smartphones, along with 823SH and 821SH models. The OEM part numbers covered are SH-01A, SH-03A, and SHBAY1. Fit the correct model before ordering — connector position and BMS handshake differ across Sharp's feature-phone and early smartphone lines.

• SH905i / SH906i platform compatibility: These models share the same 3.7V nominal voltage rail, identical connector footprint, and a compatible BMS handshake. That's why one cell covers the group — swapping between models in this cluster does not require firmware changes or resistor-pad modifications.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the SH905i platform. The BMS accepted the charge IC handshake cleanly, with no thermal flags or mid-cycle cutoff events during our test runs.
• Fuel gauge recalibration on first cycle: After fitting this cell, disable fast charging if your carrier firmware supports it, then run one full discharge-to-charge cycle before normal use. The fuel gauge IC in these Sharp models calibrates its coulomb counter against the discharge curve on the first full cycle — skipping this step lets the IC inherit the old cell's curve and produce inaccurate percentage readings.

Why the SH905i reports wrong battery percentage after a cell swap

The SH905i uses a fuel gauge IC that builds its charge model from accumulated discharge history. When the original cell degrades over hundreds of cycles, the IC recalibrates around that cell's reduced capacity curve. Drop in a fresh 700mAh cell and the IC is still reading against the old curve — so it miscounts coulombs and displays percentages that don't match actual charge state. One complete discharge from 100% to automatic shutdown, followed by a full charge with the screen on, forces the IC to reset its reference points against the new cell's actual voltage curve. After that cycle, percentage accuracy returns to normal.

Sudden shutdown at 20–30% on the replacement cell

This happens when the modem or display triggers a current draw spike that the cell voltage cannot sustain — voltage collapses below the BMS cutoff threshold even though the fuel gauge still shows charge remaining. On a brand-new cell, this is almost always a fuel gauge calibration issue, not a faulty battery. The IC has not yet mapped the new cell's voltage-sag characteristics under load, so it fails to anticipate the voltage cliff. Run the recalibration cycle described above — one full discharge and charge — and the shutdowns typically stop. If they persist past two full cycles, check that the replacement cell's BMS is not responding to a connector seating issue before assuming a defective unit.