LG VX1200 Li-ion Replacement Battery 3.7V 950mAh

LG VX1200 / LX1200 — 3.7V Li-ion Replacement Battery

This 3.7V Li-ion cell replaces the original battery in the LG VX1200 and LX1200 flip phones. Capacity is 950mAh (3.52Wh), matching the stock specification for these mid-2000s compact handsets. It slots into the rear battery bay and connects via the original three-contact terminal.

• VX1200 and LX1200 platform fit: Both models share the same battery bay dimensions, contact layout, and 3.7V nominal voltage rail. One cell covers both without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the VX1200 platform. The BMS accepted charge current correctly and the protection circuit tripped as expected at low-voltage cutoff — no thermal anomalies observed.
• Fuel gauge recalibration on first use: After fitting this cell, run one complete discharge to cutoff followed by a full charge before relying on the percentage reading. The phone's fuel gauge IC carries the old cell's discharge curve in memory and will report inaccurate percentages until it recalibrates against the new cell's actual characteristics.

Sudden shutdown at 20–30% on the VX1200 after a cell swap

This is a voltage cliff problem, not a capacity problem. The fuel gauge IC still uses the old cell's discharge curve, so it reads 25% while the actual cell voltage has already dropped below the threshold the phone's modem and display can sustain under load. When the screen backlight or a call draws current, voltage sags past the cutoff point and the phone shuts off instantly. One full discharge-charge cycle forces the coulomb counter to rebuild its map against the new cell. After that cycle, shutdowns at falsely high percentages stop.

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

Li-ion cells self-discharge during storage. If the replacement cell dropped below 2.5V per cell before installation, the BMS enters a protective lockout state and blocks normal charge current. The phone will show nothing — no charging indicator, no boot screen. Connect the phone to a charger and leave it undisturbed for 20–40 minutes. The charge IC will trickle current at a low rate to recover the cell voltage above the BMS re-enable threshold, typically around 2.9V, at which point normal charging resumes and the phone will power on.