About this replacement
LG VX1 / TM520 Series — 3.7V Li-ion Replacement Battery (LGLI-AATM)
This is a 3.7V, 1000mAh Li-ion battery that replaces the original LGLI-AATM cell. It fits the LG VX1, VX10, TM520, and TM525 mobile phones. Capacity is rated at 1000mAh (3.7Wh) — matching the original specification.
- VX1, VX10, TM520, TM525 compatibility: These four models share the same battery bay dimensions, 3.7V single-cell architecture, and connector pinout. The LGLI-AATM form factor fits all four without modification.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the TM520 platform. The BMS accepted the cell without error flags, and the charge IC completed a full cycle without interruption.
- Fuel gauge recalibration on first use: Disable any fast-charge mode for the first complete discharge-charge cycle after installation. This allows the fuel gauge IC to recalibrate its discharge curve against the new cell before high-current charging is applied to an uncalibrated cell.
Sudden shutdown at 20–30% on the replacement cell
This is a voltage cliff issue. Under load — modem transmission bursts or screen-on current — the new cell's voltage drops sharply before the fuel gauge IC registers a low-battery state. The phone shuts down because actual cell voltage collapses below the cutoff threshold, even though the reported percentage looks acceptable. Run one full discharge to near-zero, then a full charge to 100% without interruption. After that cycle the fuel gauge IC maps the real discharge curve and the shutdowns stop.
Phone not powering on after the battery sat in storage
Li-ion cells in storage self-discharge over time. If the cell drops below approximately 2.5V, the BMS enters a lockout state and the phone will not power on or show a charge indicator. Connect the phone to a wall charger — not a USB port — and leave it for 20–30 minutes without pressing the power button. The charger trickle-feeds current at a safe rate until the cell climbs above the BMS re-enable threshold, at which point normal charging resumes. Target at least 3.0V before attempting to power on.