Sony Ericsson A2218 Replacement Battery BHC-11 3.6V 750mAh

Sony Ericsson A2218 / A2638 / R300 Series — 3.6V Ni-MH Replacement Battery (BHC-11)

This is a 3.6V, 750mAh Ni-MH replacement battery for Sony Ericsson handsets using the BHC-11 cell. It fits the A2218, A2638, R300, and A2618s, along with two additional compatible models. If the original cell is swelling, dropping charge quickly, or refusing to hold voltage under screen or call load, this is the direct swap.

• A2218 / A2638 / R300 platform compatibility: These models share the same battery bay dimensions, connector pinout, and charge IC handshake. The BHC-11 cell slot is physically keyed the same across the range, and the charge circuit expects a 3.6V Ni-MH cell — this replacement meets that spec without modification.
• Bench tested on actual hardware: We ran the cell through charge and discharge cycles on the A2618s platform. The charge IC accepted the cell without fault codes, and the BMS held voltage steady across the discharge curve without premature cutoff.
• Fuel gauge recalibration on first use: After fitting this cell, run one full discharge down to auto-shutoff, then charge uninterrupted to 100%. Ni-MH cells don't carry a calibration curve from the factory — the fuel gauge IC on these handsets needs one complete cycle to map the new cell's discharge profile before percentage readings stabilise.

Why the A2218 reports wrong battery percentage after a cell swap

Sony Ericsson handsets from this era use a simple fuel gauge IC that tracks charge state by comparing current draw against a stored discharge curve from the original cell. A new Ni-MH cell has a slightly different internal resistance and discharge profile. Until the IC maps the new curve, it reads against the old one — so percentage jumps or sits frozen. One full discharge-to-shutoff followed by a complete uninterrupted charge resets the reference. After that cycle, the percentage display tracks accurately.

Sudden shutdown at 20–30% on the replacement cell

This happens when the cell voltage drops sharply under load — typically during a call or with the backlight active — faster than the fuel gauge IC predicts. Ni-MH cells have a voltage cliff near end-of-discharge that the IC hasn't yet learned on a fresh cell. The phone cuts out because the voltage falls below the low-voltage protection threshold before the displayed percentage reaches zero. Run the full recalibration cycle described above. If shutdowns continue past the second full cycle, check that the battery contacts are clean and making firm contact — a high-resistance connection at the connector causes the same voltage sag symptom.