About this replacement
KAZAM Trooper X4.5 — 3.7V Li-ion Replacement Battery (KAX45)
This is a 3.7V, 1750mAh Li-ion battery for the KAZAM Trooper X4.5 smartphone. It replaces OEM part numbers KAX45 and KAX45-XJFA007879. Fits the Trooper X4.5 and TR4543049-01 variants directly.
- Trooper X4.5 and TR4543049-01 compatibility: Both variants share the same 3.7V power rail, physical footprint, and connector pinout. The BMS on this cell communicates with the same charge IC used across the Trooper X4.5 platform, so neither model requires adaptation.
- Bench tested on actual hardware: We cycled this cell through full charge and discharge on the Trooper X4.5 platform. The BMS held voltage within spec under display and modem load, and charge termination triggered correctly at 4.2V without overrun.
- Fuel gauge recalibration on first cycle: On first use after installation, disable fast charging and run one complete discharge-to-charge cycle. The fuel gauge IC in the Trooper X4.5 is calibrated to the original cell's discharge curve — giving it one full cycle against the new cell lets the coulomb counter reset its baseline before high-current charging begins.
Sudden shutdown at 20–30% on the Trooper X4.5
This happens when the cell voltage drops sharply under load — the modem radio, screen, and CPU briefly pull more current than the cell can sustain at that state of charge. The phone's protection circuit interprets the voltage dip as a critically low cell and cuts power before the displayed percentage reaches zero. It is not a fault with the replacement cell itself. A full calibration cycle — one uninterrupted discharge from 100% to automatic shutdown, then a full charge — resets the fuel gauge and eliminates most of these premature cutoffs.
Phone not powering on after the battery sat in storage
Li-ion cells self-discharge in storage, and if voltage drops below roughly 2.5V per cell, the BMS enters a lockout state and will not respond to a normal charge attempt. Plugging in and seeing no charge indicator at all is the tell. Connect the phone to a low-current charger — a 5V/500mA USB port rather than a fast charger — and leave it for 20–30 minutes without pressing the power button. This trickle current is enough to bring the cell above the BMS re-initialisation threshold, after which normal charging resumes.