ZTE Grand S Flex Li3823T43P3h715345 Replacement Battery 3.8V 2300mAh

ZTE Grand S Flex / MF910 — 3.8V Li-Polymer Replacement Battery (Li3823T43P3h715345)

This is a 3.8V, 2300mAh Li-Polymer cell replacing OEM part Li3823T43P3h715345 and Li3820T43P3h715345. It fits the ZTE Grand S Flex smartphone and the MF910, MF910 4G LTE, and MF920 mobile hotspot series. Swap it when the original cell no longer holds a charge through a normal day.

• Grand S Flex and MF910 platform compatibility: These devices share the same 3.8V battery bay dimensions and connector pinout — 71.16 × 52.05 × 4.35mm — so one cell covers both the smartphone and the hotspot variants. The BMS handshake on each device accepts the same charge profile.
• Bench tested on actual hardware: We cycled this cell through full charge and load discharge on the Grand S Flex. The BMS held charge termination correctly at 4.35V and triggered low-voltage cutoff without false trips under steady display and modem load.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one complete discharge-charge cycle at standard rate. This lets the fuel gauge IC map the new cell's discharge curve before high-current charging pushes current into an uncalibrated counter.

Sudden shutdown at 20–30% on the replacement cell

This happens because the fuel gauge IC is still running the discharge curve from the old degraded cell. When the new cell hits a voltage point that the old curve mapped to 20–30%, the OS sees a cliff and forces shutdown — even though real capacity remains. The fix is one full uninterrupted discharge to auto-off, then a full charge without interruption. After that cycle, the coulomb counter resets against the new cell's actual curve and percentage readings stabilise.

USB fast charge not accepted on the first cycle after fitting

On the first cycle, the charge IC on the Grand S Flex may not negotiate the fast-charge protocol with a new high-impedance cell — it defaults to standard 5V/1A as a safety fallback. This is normal BMS behaviour, not a fault with the cell. Let the first full charge complete at standard rate. Fast charge negotiation typically resumes correctly from the second cycle onward once the BMS confirms cell impedance is within range.