ZTE Mono MO-01J Replacement Battery 3.8V 2400mAh Li-Polymer

ZTE Mono MO-01J / MO-01K — 3.8V Li-Polymer Replacement Battery (Li3824T43P8H655845)

This is a 3.8V, 2400mAh Li-Polymer cell built to replace the original Li3824T43P8H655845 battery. It fits the ZTE Mono MO-01J, MO-01J TD-LTE, MO-01K, and MO-01K TD-LTE smartphones. Dimensions are 64.00 × 57.70 × 4.16mm — matching the original footprint in the battery bay.

• MO-01J and MO-01K platform fit: Both the MO-01J and MO-01K series share the same battery bay geometry, connector pinout, and BMS handshake protocol. One cell covers all four variants listed without modification or adapter.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge sequences on the MO-01J platform. The BMS accepted the cell on first recognition, charge termination triggered correctly at 4.35V, and protection cutoff engaged at the expected low-voltage threshold.
• Fuel gauge recalibration on first use: After fitting this cell, disable fast charging and run one complete discharge-to-charge cycle before resuming normal use. The fuel gauge IC on these devices calibrates against the cell's discharge curve — skipping this step causes the percentage readout to lag or jump until the IC resets its coulomb counter baseline.

Sudden shutdown at 20–30% on the MO-01J after a cell swap

This happens because the fuel gauge IC is still running the discharge model it built for the degraded original cell. A worn cell has a compressed voltage curve, so the IC shifts cutoff high to compensate. When a new cell with a full voltage range is installed, the IC triggers shutdown early — the phone cuts out well before the cell is actually depleted. The fix is one full discharge cycle from 100% to automatic shutdown, then a full charge without interruption. After that cycle, the coulomb counter resets its reference point against the new cell's actual curve.

Phone won't power on after the replacement battery sat in storage

Li-Polymer cells self-discharge during storage, and if the cell drops below approximately 2.5V, the BMS enters lockout mode to prevent cell damage — the phone will not respond to the power button or show a charging indicator. Connect the phone to a wall charger, not a USB port, and leave it for 15–20 minutes without attempting to power it on. The charge IC on the MO-01J will trickle current into the cell at a reduced rate until it clears the BMS recovery threshold, at which point normal charging resumes. If there is still no response after 30 minutes on a wall charger, check that the battery connector is fully seated.