Allstar Z818L Replacement Battery 3.8V 2300mAh Li-ion

Allstar Z818L / Z818G (Straight Talk) — 3.8V Li-ion Replacement Battery

This 3.8V, 2300mAh lithium-ion cell replaces the factory battery in the Allstar Z818L and Z818G smartphones sold through Straight Talk. When the original cell swells, loses hold, or refuses to charge past a low percentage, this swap restores the phone to a working power supply. Dimensions are 72.90 × 53.60 × 4.70mm — measure your existing cell before ordering.

• Z818L and Z818G share the same cell: Both handsets run the same motherboard power rail at 3.8V nominal and use the same physical bay. The connector pinout and BMS handshake requirements are identical across both variants, so one cell covers both models.
• Bench tested on actual hardware: We cycled this cell through a full discharge-charge sequence on the Z818 platform and confirmed the BMS accepted the charge profile without triggering an overcurrent cutoff. Voltage at delivery sits between 3.6V and 3.7V — a safe shipping state.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC map the new cell's actual discharge curve before the charge IC pushes higher current into an uncalibrated cell — preventing early percentage jumps.

Sudden shutdown at 20–30% on the Z818 after a cell swap

The Z818's fuel gauge IC was calibrated against the original cell's discharge curve. A new cell has a slightly different voltage-to-capacity slope, so the gauge reads 25% while the actual cell voltage has already dropped to the cutoff threshold under modem or screen load. The phone shuts down because the hardware voltage floor is hit before the software percentage reaches zero. One full discharge-charge cycle — draining to automatic shutdown, then charging uninterrupted to 100% — resets the coulomb counter and aligns the gauge to the new cell.

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

If this cell spent time in storage below 3.0V per cell, the BMS may have tripped its deep-discharge lockout to protect the lithium chemistry. The phone will show no response to the power button and may not show a charging indicator for the first several minutes on the cable. Connect to a wall adapter — not a PC port — and leave it for 15–20 minutes without touching it. Once the cell climbs back above 3.2V, the BMS releases the lockout and the phone boots normally.