About this replacement
KAZAM Thunder2 5.0 — 3.8V Li-Polymer Replacement Battery (KQQ50)
This 3.8V 2000mAh Li-Polymer cell replaces the original battery in the KAZAM Thunder2 5.0 smartphone (model TH25014-01). It matches the OEM part number KQQ50 and fits the phone's internal bay without modification. Capacity is 2000mAh at 7.6Wh — identical to the factory specification.
- Thunder2 5.0 and TH25014-01 fitment: Both model references share the same battery bay dimensions, connector pinout, and BMS handshake protocol. The physical cell measures 76.00 × 58.95 × 3.90mm — a tight tolerance match to the original compartment. No adapter or rewiring needed.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the Thunder2 5.0 platform. The BMS accepted the cell without fault codes, the charge IC reached full termination correctly, and voltage held stable under combined screen and modem load.
- Fuel gauge recalibration on first use: After installation, disable fast charging and run one full discharge down to automatic shutdown, then charge uninterrupted to 100%. This gives the fuel gauge IC a complete discharge curve to map against the new cell — skipping this step causes erratic percentage readings for the first several days.
Sudden shutdown at 20–30% on the Thunder2 5.0
The Thunder2 5.0's modem and display pull current in short spikes. An aged cell cannot sustain voltage under that load — it drops below the BMS cutoff threshold and the phone shuts off even though the fuel gauge still shows charge remaining. This is a voltage cliff, not a capacity problem. A new cell with lower internal resistance holds voltage through those spikes. After fitting this replacement, run one full calibration cycle so the fuel gauge IC recalculates the cliff point on the new cell's actual discharge curve.
Phone won't power on after sitting in a drawer for months
Li-Polymer cells self-discharge during storage. If the cell voltage drops below approximately 2.5V per cell, the BMS locks out to prevent damage — the phone will not respond to a charger or power button. Connect the phone to a low-current charger (a standard 5W USB wall adapter, not a fast charger) and leave it undisturbed for 30–60 minutes. The BMS recovery circuit trickle-charges the cell back above the lockout threshold before allowing normal charging to resume. If the screen shows no charging indicator after 90 minutes, check that the charger output sits at 5V.