Sharp SH22 Replacement Battery 3.7V 650mAh Li-ion

Sharp SH-06A / SH-07A — 3.7V Li-ion Replacement Battery (SH22, ASH29242)

This is a 3.7V 650mAh (2.41Wh) Li-ion replacement battery for the Sharp SH-06A and SH-07A smartphones. It matches the original SH22 cell dimensions at 47.44 × 37.40 × 3.85mm and drops into the same battery bay without modification. Fit either model with the same part.

• SH-06A and SH-07A compatibility: Both models share the same battery bay dimensions, connector pinout, and BMS handshake protocol — one cell covers both. The fuel gauge IC on each device reads voltage and current from the same register addresses, so no firmware mismatch occurs.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on an SH-series test unit. The BMS accepted the cell without triggering a fault flag, and the charge IC held the correct 4.2V cutoff at end of charge.
• Fuel gauge recalibration on first cycle: After fitting this battery, disable fast charging and run one complete discharge-charge cycle before returning to normal use. This gives the fuel gauge IC a clean discharge curve from the new cell to calibrate its coulomb counter against — skipping this step can cause the percentage readout to drift or report sudden low battery.

Why the SH-06A reports wrong battery percentage after a cell swap

The SH-06A uses a fuel gauge IC that builds its capacity model from the previous cell's charge and discharge history. When a new cell goes in, that model is stale — the IC is predicting voltage curves it no longer sees. The result is a percentage reading that doesn't match actual remaining charge. One full discharge-to-shutdown followed by a full charge resets the coulomb counter against the new cell's actual curve. After that single cycle, the readout stabilises.

Sudden shutdown at 20–30% on the replacement cell

This happens when the modem or display draws a current spike and the cell voltage drops below the BMS cutoff threshold before the fuel gauge has time to update its register. The phone interprets this as a dead battery even though the gauge was showing 20–30%. It is more common in the first few cycles on a fresh cell, before the internal resistance settles and the fuel gauge IC has recalibrated. Run two full discharge-charge cycles and confirm the resting cell voltage reads at or above 3.7V before closing the phone back up.