LGIP-420A Replacement Battery for LG AX500 3.7V 1700mAh

LG AX500 / UX500 — 3.7V Li-ion Replacement Battery (LGIP-420A)

This is a 3.7V, 1700mAh Li-ion cell replacement for the LG AX500 and UX500 smartphones. It slots into the same battery bay as the original LGIP-420A and restores power to a phone that no longer holds charge through a full day of use. Capacity figure is 1700mAh — sourced from product data, not estimated.

• AX500 and UX500 compatibility: Both models share the same battery bay dimensions, connector pinout, and 3.7V nominal voltage rail. The LGIP-420A cell fits either device without modification. The BMS handshake is identical across the two variants, so the phone's charge IC accepts the new cell on first boot.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the AX500 platform. The BMS reported correct voltage at each charge stage, and the protection circuit tripped as expected at the low-voltage cutoff threshold — no runaway, no false full-charge signal.
• Fuel gauge recalibration after cell swap: On first use after installation, disable fast charging if available and run one complete discharge-to-charge cycle. This lets the fuel gauge IC map its internal table to the new cell's actual discharge curve before estimating state-of-charge under cellular modem load.

Sudden shutdown at 20–30% on the AX500 after a cell swap

The AX500's fuel gauge IC stores a learned discharge curve from the old cell. When a new cell goes in, the gauge's calibration no longer matches the actual voltage-to-capacity relationship of the replacement. At around 20–30% reported charge, the phone's modem or display draws a current spike that the new cell can sustain — but the gauge reads the resulting voltage dip as a crash below the shutdown threshold. One full discharge-charge cycle forces the coulomb counter to rebuild its internal table. After that cycle, the phone should stop cutting out early.

Device not powering on after the replacement cell sat in storage

Li-ion cells self-discharge in storage. If the replacement battery dropped below approximately 2.5V per cell before installation, the BMS protection circuit will have triggered a lockout to prevent charging a deeply discharged cell. The phone will show no response — no boot, no charge indicator. Connect the phone to a wall charger and leave it undisturbed for 15–20 minutes; some chargers deliver a trickle recovery current that nudges the cell above the BMS re-enable threshold. Once the charge LED activates, normal charging can resume.