Simvalley SX-325 Compatible Battery 3.7V 1050mAh PX-3402

Simvalley SX-325 — 3.7V Li-ion Replacement Battery (PX-3402)

This 3.7V 1050mAh lithium-ion battery is a direct replacement for the Simvalley SX-325 smartphone. It fits the OEM part numbers PX-3402, PX-3402-675, and PX-3402-912. Install it when the original cell no longer holds a charge or fails to power the handset through normal use.

• SX-325 compatibility: All three OEM part variants — PX-3402, PX-3402-675, and PX-3402-912 — share the same 3.7V nominal voltage rail, connector pinout, and BMS handshake protocol. The same physical cell dimensions (58.00 × 37.05 × 5.20mm) apply across all three, so one replacement covers the full SX-325 production run.
• Bench tested on actual hardware: We cycled this cell through a full discharge-to-cutoff and charge-to-termination sequence on the SX-325 platform. The BMS accepted charge termination correctly, and protection circuits triggered at expected voltage thresholds with no false cutoffs.
• Fuel gauge recalibration after swap: On first use after installing this cell, disable fast charging if your SX-325 supports it, then run one complete discharge down to auto-shutoff followed by a full charge. This lets the fuel gauge IC map its coulomb counter against the new cell's actual discharge curve before fast-charge current is applied.

Why the SX-325 reports wrong battery percentage after a cell swap

The SX-325 fuel gauge IC stores a charge curve calibrated to the original cell's internal impedance profile. When a new cell goes in, that stored curve no longer matches the actual discharge behaviour of the replacement — so the OS reads a percentage based on stale data. You may see the indicator sit at 100% longer than expected, then drop sharply. One full discharge-to-shutoff followed by an uninterrupted charge to 100% forces the IC to rebuild its internal model against the new cell. After that cycle, percentage reporting stabilises.

Sudden shutdown at 20–30% on the replacement cell

This happens when the cell voltage collapses under high-current load — typically when the modem transmits or the screen brightness spikes — before the fuel gauge reads zero. The new cell's open-circuit voltage looks healthy at rest, but under draw it drops below the BMS cutoff threshold before the gauge expects it. This is a fuel gauge calibration lag, not a faulty cell. Run one full cycle without fast charging: discharge to auto-shutoff, charge uninterrupted to 4.2V termination, and the shutoffs at 20–30% should stop.