AK-V500 Emporia Prime Replacement Battery 3.7V 950mAh

Emporia Prime V500 Series — 3.7V Li-ion Replacement Battery (AK-V500)

This is a 3.7V, 950mAh Li-ion replacement battery for the Emporia Prime flip phone, including the Prime V500 and Prime V500.3G. It replaces the original AK-V500 cell when the factory battery no longer holds charge or fails to power the device.

• Prime V500 and V500.3G compatibility: Both variants run the same 3.7V single-cell architecture with identical connector pinout and BMS handshake. One cell fits both builds without modification.
• Bench tested on actual hardware: We ran this cell through a full charge and discharge cycle on a Prime V500.3G unit. The BMS accepted the cell without fault codes, and the charge IC ramped to full current within the first few minutes of the initial charge.
• Fuel gauge recalibration on first use: After fitting this cell, disable fast charging if available and let the phone complete one full discharge-to-charge cycle before resuming normal use. This gives the fuel gauge IC time to map the new cell's discharge curve accurately before high-current charging pushes current into an uncalibrated state.

Why the Emporia Prime reports wrong battery percentage after a cell swap

The Prime's fuel gauge IC stores a learned discharge curve from the original cell. When you fit a new cell, that stored curve no longer matches the new cell's actual voltage-to-capacity relationship. The gauge reads voltage and maps it against old data, so it reports incorrect percentages — often too high early in discharge and then dropping suddenly. One complete discharge cycle, down to automatic shutdown and back to 100%, forces the IC to relearn the curve against the new cell.

Sudden shutdown at 20–30% on the replacement cell

This happens when the cell voltage drops sharply under the combined load of the 3G modem and screen — a voltage cliff the fuel gauge did not predict. The BMS triggers a hard cutoff before the displayed percentage reaches zero. It is not a faulty cell; it is an uncalibrated gauge reading a flat part of the discharge curve as if it were mid-charge. Run one full discharge cycle to let the coulomb counter reset, then charge back to 4.2V before normal use.