Caseroxx 1100 Replacement Battery 3.7V 1200mAh Li-ion

Caseroxx 1100 — 3.7V Li-ion 1200mAh Replacement Battery

This is a 3.7V lithium-ion cell rated at 1200mAh (4.44Wh) from Caseroxx's X-Longer series. It fits the 1100 smartphone when the original cell can no longer hold a usable charge. Physical dimensions are 53.00 × 33.90 × 5.70mm — confirm these against your existing cell before fitting.

• 1100 platform fit: The 1100 uses a single-cell 3.7V nominal architecture with a standardised connector pinout. This cell matches that voltage rail and physical envelope, so the BMS on the mainboard can read charge state and apply cutoff thresholds correctly.
• Bench tested on actual hardware: We cycled this cell through full discharge and recharge on a 3.7V single-cell rig. The BMS accepted the cell without triggering overcurrent cutoff, and charge termination fired correctly at 4.2V.
• First-cycle fuel gauge reset: On first use after installation, disable fast charging and run one complete discharge-to-charge cycle. This lets the fuel gauge IC map the new cell's discharge curve before reporting percentage to the OS — skipping it causes erratic readings from the first hour.

Why the 1100 reports wrong battery percentage after a cell swap

The fuel gauge IC on the 1100 mainboard stores a learned discharge curve from the original cell. When a new cell goes in, that stored curve no longer matches the actual voltage-to-capacity relationship of the replacement. The OS then reads percentage from a mismatched model, so it can show 40% while the cell is actually near cutoff. One full discharge cycle — taken to automatic shutdown, then charged uninterrupted to 100% — forces the coulomb counter to rebuild its reference map against the new cell.

Sudden shutdown at 20–30% on the replacement cell

This happens when the cell voltage drops below the mainboard's cutoff threshold under load — typically during screen-on or a data burst — even though the reported percentage looks safe. The gauge IC is still using the old cell's curve, so it overestimates remaining capacity. The fix is the same full recalibration cycle above. If shutdowns persist after two full cycles, check resting cell voltage with a multimeter: a healthy cell at 30% reported charge should read between 3.70V and 3.80V at rest.