ZTE Z850 Replacement Battery Li3824T44P3H706145 3.85V 2450mAh

ZTE Z850 / Grand X2 — 3.85V Li-ion Replacement Battery (Li3824T44P3H706145)

This is a 3.85V, 2450mAh (9.43Wh) Li-ion cell built to the same dimensions as the factory battery in the ZTE Z850, Grand X2, and Grand X 2. It fits all three model names — ZTE used the same battery across this lineup. Install it when your original cell no longer holds a charge or fails to power the device through a normal day.

• Z850 / Grand X2 fitment: All three model names share an identical battery bay, connector pin-out, and BMS handshake protocol. One cell covers the full group — no adapter or modification needed.
• Bench tested on actual hardware: We ran this cell through a full charge-discharge cycle and confirmed BMS communication, charge termination, and voltage hold under load. The cell hit 3.85V nominal and the protection circuit tripped correctly at the low-voltage cutoff.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging for one complete discharge-charge cycle. The fuel gauge IC in the Z850 is still calibrated to your old cell's discharge curve. Let it map the new cell at a steady current rate before re-enabling high-current charging.

Sudden shutdown at 20–30% on the Z850 after a cell swap

This happens because the fuel gauge IC is reading a state-of-charge curve that belongs to the old, degraded cell. A fresh cell holds a steeper voltage curve near the bottom of its charge range. When the modem fires a high-current burst — during a call or a data transfer — the phone's actual cell voltage briefly dips below what the gauge expects, and the protection circuit cuts power. One full discharge down to auto-off followed by a full charge resets the coulomb counter and eliminates most of these premature shutdowns.

ZTE Z850 not powering on after the replacement battery sat in storage

Li-ion cells self-discharge in storage. If this cell was stored long enough to drop below 2.5V, the BMS enters a deep-discharge lockout state and the phone will show no response when you press power. Connect the phone to a wall charger — not a PC port — and leave it for 20–30 minutes without pressing any button. The charge IC will trickle current into the cell until it clears the BMS lockout threshold, typically around 2.9–3.0V, at which point normal charging resumes.