About this replacement
KAZAM Thunder2 4.5L — 3.8V Li-ion Replacement Battery (KQ45L)
This is a 3.8V, 1700mAh Li-ion cell for the KAZAM Thunder2 4.5L smartphone. It fits the Thunder2 4.5L, Thunder 2 4.5L, and Thunder 2 Q4.5L variants — all share the same battery bay and connector. The KQ45L part number covers all three model name formats KAZAM used across regional markets.
- Thunder2 4.5L variant compatibility: The Thunder2 4.5L, Thunder 2 4.5L, and Thunder 2 Q4.5L are the same hardware platform with different regional branding. The battery connector, voltage rail, and BMS handshake are identical across all three — one cell fits them all.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on Thunder2 4.5L hardware. The BMS accepted the cell on first connection, charge termination triggered correctly at 4.2V, and the protection circuit tripped cleanly at the low-voltage threshold under load.
- Fuel gauge recalibration on first use: Disable fast charging for the first full discharge-charge cycle after installation. The fuel gauge IC in the Thunder2 4.5L calibrates its coulomb counter against the cell's actual discharge curve — letting it run one uninterrupted cycle at standard current gives the IC accurate data before higher charge currents are applied.
Sudden shutdown at 20–30% on the Thunder2 4.5L after a cell swap
This happens because the fuel gauge IC is still using the discharge curve from the old, degraded cell. A new cell has a steeper voltage drop at the low end of its curve than the worn cell it replaced. The phone's modem or screen draws a current spike, the voltage dips below the BMS cutoff threshold momentarily, and the phone shuts off even though the displayed percentage looks safe. One full discharge-charge cycle — run from 100% down to automatic shutdown, then charged to 100% — lets the coulomb counter remap against the new cell and this behaviour stops.
Phone reports wrong battery percentage after replacing the KQ45L cell
The fuel gauge IC stores a learned model of the previous cell's impedance and capacity. When a new cell goes in, that stored model is wrong from the first moment. The percentage displayed can read 80% and drop to 10% within minutes, or the phone may shut down well above 0%. A single full discharge from 100% to cutoff — without interruption — followed by an uninterrupted charge back to 100% forces the IC to reset its reference points against the actual new cell. After that cycle, percentage readings stabilise.