About this replacement
BLU Yezz YZ1120 — 3.7V Li-ion Replacement Battery (C535051145T)
This is a 3.7V Li-ion cell rated at 1400mAh (5.18Wh), built to the same form factor as the original C535051145T. It fits the BLU Yezz and YZ1120 smartphones. Swap it in when the original cell no longer holds a charge or causes unexpected shutdowns.
- Yezz and YZ1120 fit: Both models share the same battery bay dimensions (53.36 x 49.80 x 4.95mm), connector pinout, and BMS handshake protocol — a single cell covers the full Yezz line under part number C535051145T.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on a YZ1120 unit, confirming the BMS accepted the cell without triggering a protection cutoff and that the fuel gauge IC registered capacity correctly after one full cycle.
- First-cycle fuel gauge calibration: On first use after installation, disable fast charging and run one complete discharge-charge cycle at standard current. 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 Yezz reports wrong battery percentage after a cell swap
The fuel gauge IC in the YZ1120 stores a learned discharge curve from the original cell. When a new cell goes in, that stored curve no longer matches actual cell behaviour. The OS reads a percentage based on stale data, so the number shown can lag or jump. One full discharge down to auto-shutoff, followed by a full charge, forces the coulomb counter to rebuild its reference against the new cell.
Sudden shutdown at 20–30% on the replacement cell
This happens when the cell voltage drops sharply under high-draw loads — modem bursts, screen at full brightness, or GPS — faster than the fuel gauge IC predicted. The BMS reads a voltage cliff and cuts power to protect the cell, even though the percentage display still showed headroom. It is not a faulty cell; it is an uncalibrated gauge. Run two full discharge-charge cycles at standard current and the shutoffs will stop once the IC has an accurate low-voltage threshold mapped to this cell's curve.