LGIP-400N Compatible Battery for LG P509 3.7V 1500mAh

LG Optimus S / P509 Series — 3.7V Li-ion Replacement Battery (LGIP-400N)

This is a 3.7V, 1500mAh Li-ion battery for the LG P509, Optimus S (LS670), and MS690 smartphones. It replaces the original LGIP-400N cell and shares cross-compatible part numbers SBPL0102301, LGIP-400V, and SBPL0102302. The battery slots into the standard rear compartment with no hardware modification.

• Optimus S platform compatibility: The P509, LS670, and MS690 all run the same LG Qualcomm MSM7627 platform and share an identical battery bay, connector pitch, and BMS handshake protocol — that is why one cell covers all three variants.
• Bench tested on actual hardware: We ran this cell in an LS670 and logged the BMS charge acceptance across three full cycles. The protection circuit held cutoff at 4.20V on charge and tripped at 3.0V on discharge with no anomalies detected.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging and let the phone run one complete discharge-to-charge cycle. This gives the fuel gauge IC time to map the new cell's discharge curve before the charge controller starts pushing higher current into an uncalibrated cell.

Why the P509 reports wrong battery percentage after a cell swap

The LG Optimus S uses a coulomb counter in the fuel gauge IC that builds its capacity model from cycle history on the original cell. When you install a fresh cell, that stored model no longer matches the new cell's discharge curve. The phone reads voltage and interprets it against stale calibration data, so the percentage shown can be several points off. One full discharge below 10% and a complete charge to 100% resets the calibration baseline. After that cycle the reported percentage tracks the actual state of charge correctly.

Sudden shutdown at 20–30% on the replacement cell

This happens when the modem radio or screen backlight spikes current draw and the cell voltage sags below the BMS cutoff threshold before the fuel gauge registers the drop. It is a voltage-cliff failure — the cell still shows charge percentage but cannot sustain the voltage under load. The fix is to complete two full calibration cycles so the fuel gauge IC learns the actual usable voltage window of the new cell. If shutdowns persist past two cycles, check that the battery connector pins seat flush — a partial contact increases resistance and worsens voltage sag under load.