Emporia Supereasy AK-S3M Replacement Battery 3.8V 2500mAh

Emporia Supereasy SE — 3.8V Li-Polymer Replacement Battery (AK-S3M)

The AK-S3M is a 3.8V 2500mAh Li-Polymer cell that fits the Emporia Supereasy and SE smartphones. It replaces a failing or depleted original battery when the phone can no longer hold a usable charge. Physical dimensions are 72.00 × 52.00 × 5.30mm — confirm these against your existing cell before fitting.

• Supereasy and SE coverage: Both the Supereasy and SE variants share the same battery bay dimensions, connector pinout, and BMS handshake protocol, so one cell covers both. Voltage rail is 3.8V nominal with the same charge termination threshold across the platform.
• Bench tested on actual hardware: We ran the AK-S3M through full charge and load cycles on the Supereasy platform. The BMS accepted charge termination correctly and protection circuits triggered at expected voltage floor without nuisance cutoffs.
• Fuel gauge recalibration on first use: After fitting, disable any fast-charge mode and run one complete discharge-to-charge cycle at standard current. This lets the fuel gauge IC map the new cell's discharge curve before high-current charging pushes amps into an uncalibrated register.

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

A fresh Li-Polymer cell has a steeper voltage cliff than a worn original, meaning the phone's modem or display draws enough current to collapse the cell voltage below the BMS cutoff threshold — even when the fuel gauge still reads 20–30%. The fuel gauge IC is still calibrated to the old cell's internal resistance profile, so it misreads remaining capacity under load. This is not a faulty battery. One full discharge-charge cycle without fast charging resets the coulomb counter against the actual new cell curve. After that cycle, the shutdown threshold should align correctly with real remaining capacity.

Phone will not power on after the AK-S3M sat in storage

Li-Polymer cells self-discharge slowly in storage. If the replacement cell drops below approximately 2.5V, the BMS enters lockout mode and will not pass current to the phone — the device appears completely dead. Connect the phone to a wall charger and leave it for 15–20 minutes without attempting to power it on. Most BMS circuits include a trickle pre-charge path that slowly raises cell voltage back above the 2.7V recovery threshold before unlocking full charge current. If the charge indicator light does not appear within 30 minutes, check the charging cable and port before assuming a cell fault.