Motorola C333 Li-ion Replacement Battery 3.7V 600mAh

Motorola C330 / C331 / C332 / C333 — 3.7V Li-ion Replacement Battery

This is a 3.7V, 600mAh Li-ion replacement cell for the Motorola C330, C331, C332, and C333 mobile handsets. These early-2000s compact phones share a common battery bay and connector, so one cell covers the whole family. Capacity is 2.22Wh, matching the original specification.

• C330 / C331 / C332 / C333 platform fit: All four handsets use the same 3.7V single-cell pack with an identical connector pitch and locking tab. The BMS handshake on each model expects the same charge termination voltage, so the cell slots in without wiring changes.
• Bench tested on actual hardware: We cycled this cell through a full discharge and charge sequence on the C333 platform. The BMS accepted the cell on first connect, charge termination triggered correctly at 4.2V, and the protection circuit tripped cleanly on a simulated over-discharge event below 2.5V.
• Fuel gauge recalibration on first use: After fitting this cell, run one complete discharge down to automatic shutoff, then charge uninterrupted to 100% before normal use. The C333 fuel gauge IC uses a stored discharge curve from the old cell — one full cycle overwrites it with the new cell's actual curve, so percentage readings stay accurate.

Why the C333 reports wrong battery percentage after a cell swap

The C333 stores a learned discharge curve in the fuel gauge IC — built up over hundreds of cycles on the original cell. When a new cell goes in, the IC still references that old curve. The mismatch means the phone can report 40% remaining while the actual cell voltage is already near cutoff. One full uninterrupted discharge-to-charge cycle forces the IC to relearn against the new cell's real voltage profile. After that cycle, percentage readouts track accurately.

Sudden shutdown at 20–30% on the replacement cell

This happens when the cell voltage drops below the modem's minimum rail during a transmit burst — even though the fuel gauge still reads 20–30%. A new Li-ion cell at 600mAh has a steep voltage cliff toward the bottom of its discharge curve. The phone's processor detects the voltage sag and shuts down to protect the BMS, regardless of the displayed percentage. After the fuel gauge recalibration cycle described above, the shutoff point moves back in line with the cell's actual usable range — expect clean operation down to roughly 3.4V under load.