LGIP-A750 LG KE820 Replacement Battery 3.7V 750mAh

LG KE820 / KE850 Series — 3.7V Li-ion Replacement Battery (LGIP-A750)

This is a 3.7V, 750mAh lithium-ion cell that replaces the original LGIP-A750 and LGIP-C800 batteries. It fits the LG KE820, KE850, KG99, and KB6100 flip phones — compact mid-2000s handsets whose original cells have typically degraded past usable capacity after years of storage or light cycling. Dimensions are 44.09 × 38.14 × 4.75mm.

• KE820 / KE850 platform compatibility: These models share the same battery bay geometry, connector pinout, and BMS handshake protocol. The LGIP-A750 and LGIP-C800 part numbers are interchangeable across this family — same voltage rail, same contact layout, same charge IC communication.
• Bench tested on actual hardware: We cycled this cell through the KE850 charge IC and confirmed the BMS accepted the cell without tripping a fault code. Charge termination occurred correctly at 4.2V, and the protection circuit responded to short-circuit simulation within spec.
• Fuel gauge recalibration on first use: After fitting this cell, run the phone from a full charge down to automatic shutdown — do not interrupt the cycle. The fuel gauge IC on these LG handsets calibrates its discharge curve on the first full cycle. Skipping this step causes erratic percentage readings for weeks.

Sudden shutdown at 20–30% on the KE820 after a cell swap

The KE820's fuel gauge IC retains the discharge curve of the old, degraded cell in memory. When a fresh 750mAh cell is installed, the IC expects voltage to sag earlier than it actually does — until it sees an actual cliff. On the first few cycles, the phone may cut power when the new cell still has usable charge remaining, because the gauge flags a low-voltage condition based on stale calibration data. Run one uninterrupted discharge-to-shutdown cycle and the IC rewrites its curve against the new cell. After that cycle, shutdowns at 20–30% should stop.

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

Li-ion cells shipped or stored for extended periods can drop below 3.0V per cell — sometimes below the 2.5V threshold where the BMS engages a lockout to prevent damage. The KE820 will show no signs of life: no boot screen, no charging indicator. Connect the phone to a low-current USB charger and leave it for 20–30 minutes before attempting to power on — the charge IC needs time to trickle current into the cell until the BMS releases its lockout. If the phone still won't respond, check that the charger is delivering at least 5V at the port.