About this replacement
Kyocera DuraMax / E4210 / E4225 / E4277 — 3.7V Li-ion Replacement Battery (SCP-43LBPS)
This is a 3.7V, 1450mAh Li-ion replacement battery for the Kyocera DuraMax and its E4210, E4225, and E4277 variants. It matches the original cell footprint at 53.90 × 34.00 × 7.20mm. OEM part numbers SCP-43LBPS and 5AAXBT048GEA both cross-reference to this cell.
- DuraMax / E42xx series fit: The E4210, E4225, and E4277 share the same battery bay dimensions, connector pinout, and BMS handshake protocol as the DuraMax — one cell covers the full group.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a DuraMax unit. The BMS accepted the cell without a protection trip, and the fuel gauge IC registered a full 1450mAh draw before cutoff voltage was reached.
- Fuel gauge recalibration on first install: On first use after installation, disable fast charging and run one complete discharge-to-charge cycle. This gives the fuel gauge IC time to map its coulomb counter against the new cell's discharge curve before high-current charging begins on an uncalibrated cell.
Sudden shutdown at 20–30% on the DuraMax after a cell swap
The DuraMax modem and screen together draw enough current to cause a brief voltage sag on a new cell. If the fuel gauge IC is still calibrated to the old cell's discharge curve, it misreads remaining capacity. The phone's protection circuit then sees a voltage reading that falls below the shutdown threshold — even though the cell has charge left. One full discharge-charge cycle without fast charging resets the coulomb counter and clears this behaviour.
OS reporting erratic or jumping battery percentage after replacement
After a cell swap, the fuel gauge IC carries forward calibration data from the old cell. The new cell's impedance and discharge curve differ enough that the percentage readout can jump — sometimes several points in either direction — during normal use. This is a calibration mismatch, not a fault in the cell itself. Charge the phone to 100%, allow it to discharge fully without interruption, then recharge to 100% to give the IC a clean reference cycle. The readout stabilises at 3.7V nominal after that cycle completes.