KAZAM Thunder 350L TH305L Replacement Battery 3.8V 2000mAh

KAZAM Thunder 350L — 3.8V Li-ion Replacement Battery (TH305L)

This is a 3.8V, 2000mAh Li-ion battery for the KAZAM Thunder 350L smartphone. It replaces part number TH305L when the original cell has degraded, lost capacity, or failed outright. Voltage and physical dimensions match the original: 76.66 × 60.95 × 3.85mm.

• Thunder 350L fit: The Thunder 350L uses a removable 3.8V single-cell Li-ion pack on a connector that matches this cell exactly. The BMS embedded in the pack communicates charge state back to the phone's fuel gauge IC — a mismatch here causes erratic percentage readings and early shutdowns.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the bench, monitoring BMS handshake, cutoff voltages, and charge acceptance. The protection circuit tripped correctly at low-voltage cutoff and released cleanly on reconnection at normal charge.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one complete discharge-to-charge cycle at standard rate. This lets the fuel gauge IC map the new cell's discharge curve before high-current charging pushes current into an uncalibrated state.

Why the Thunder 350L reports wrong battery percentage after a cell swap

The Thunder 350L tracks charge state using a fuel gauge IC that learns the cell's discharge curve over time. When you install a new cell, the IC is still calibrated to the old cell's internal resistance and voltage profile. Until it recalibrates, the displayed percentage drifts — often reading 20–30% higher or lower than the actual state of charge. One full slow-charge cycle resets the coulomb counter against the new cell and brings the percentage back in line.

Sudden shutdown at 20–25% on the replacement cell

This happens when the modem, screen, or both pull a brief high-current spike that the cell cannot sustain without the voltage sagging below the BMS cutoff threshold. The phone interprets this as a dead cell and shuts down, even though the percentage indicator still shows charge remaining. It is most common in the first few cycles on a new cell before the BMS and fuel gauge IC have aligned their voltage references. Charge to 100% and discharge fully twice — after that, the cutoff threshold and the displayed percentage should converge correctly.