About this replacement
ZTE Grand X 3 / Z959 — 3.8V Li-Polymer Replacement Battery (Li3831T43P4H826247)
This is a 3.8V, 2500mAh Li-Polymer cell that replaces the original battery in the ZTE Grand X 3, Grand X 3 LTE, Z959, and Zmax Champ. It fits the same footprint as the OEM unit at 81.30 × 61.90 × 4.70mm. If your Grand X 3 is shutting down unexpectedly, losing charge quickly, or won't hold any charge at all, this cell addresses the failed original.
- Grand X 3 / Z959 platform fit: These models share the same battery bay dimensions, connector pinout, and BMS handshake protocol — one cell covers the full variant list including the LTE and Zmax Champ without modification.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the Grand X 3 platform and confirmed the BMS accepts the charge handshake correctly, with no cutoff trips during a standard draw cycle.
- Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one complete discharge-to-charge cycle. This lets the fuel gauge IC map its coulomb counter against the new cell's discharge curve before high-current charging is applied to an uncalibrated cell.
Sudden shutdown at 20–30% on the Grand X 3 after a cell swap
This happens when the fuel gauge IC is still running its lookup table against the old cell's discharge curve. The new cell hits a voltage cliff under modem or display load before the OS registers low battery. The phone cuts out because actual cell voltage drops below the protection threshold while the OS still shows 20–30% remaining. Running one full discharge cycle without fast charging forces the coulomb counter to rebuild its reference table against the new cell.
Device not powering on after the replacement cell sat in storage
Li-Polymer cells self-discharge in storage, and if voltage drops below approximately 2.5V, the BMS trips a lockout to prevent damage to the cell. The phone will show nothing on screen — no charge indicator, no boot. Connect the phone to a wall charger rated at least 5V/1A and leave it for 20–30 minutes before attempting to power on. The charge IC will trickle current into the cell until voltage climbs above the BMS re-enable threshold, after which normal charging resumes.