About this replacement
Wiko Ozzy / Ozzy Double Sim — 3.7V Li-ion Replacement Battery (OZZY)
This 3.7V 1100mAh Li-ion cell replaces the factory battery in the Wiko Ozzy and Ozzy Double Sim smartphones. It fits both single-SIM and dual-SIM variants of the Ozzy — same physical dimensions at 65.10 × 44.00 × 4.50mm and same voltage rail. Swap it when the original cell no longer holds charge through a normal day.
- Ozzy and Ozzy Double Sim compatibility: Both models share the same PCB voltage rail, connector pinout, and BMS handshake protocol. One cell fits either variant — no hardware differences affect the swap.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the Ozzy platform. The BMS accepted the cell without fault codes, and the charge IC reached full-charge termination correctly on each cycle.
- First cycle after installation: On first use, disable any fast-charge mode and run one full discharge-to-charge cycle. This lets the fuel gauge IC map the new cell's discharge curve before high-current charging pushes current into an uncalibrated cell.
Why the Ozzy reports the wrong battery percentage after a cell swap
The Ozzy's fuel gauge IC builds its percentage model from the discharge curve of the original cell over many cycles. When you install a new cell, that stored curve no longer matches actual cell behaviour. The gauge reads voltage and converts it to a percentage using the old map — which is now wrong. One complete discharge from 100% down to auto-shutdown, followed by a full charge to 100%, forces the coulomb counter to recalibrate against the new cell and restore accurate readings.
Sudden shutdown at 20–30% on the replacement cell
This happens when the cell voltage drops sharply under load — modem transmit bursts and screen brightness spikes draw enough current to pull the cell below the BMS cutoff threshold even while the gauge still reads 20–30%. It is a voltage-sag event, not a capacity fault. Let the phone power back on and check the resting voltage — if it climbs back above 3.5V within 30 seconds, the cell is fine and the fuel gauge simply needs a full recalibration cycle to account for the new cell's internal resistance profile.