Evolution EV-128MRS Compatible Battery 1.2V 1200mAh Ni-MH

Evolution EV-128MRS — 1.2V Ni-MH Replacement Battery

This is a 1.2V Ni-MH replacement battery rated at 1200mAh (1.44Wh) for the Evolution EV-128MRS portable media player. It replaces the original cell when charge capacity has dropped to the point where playback cuts out early or the device fails to power on. Dimensions are 66.78 × 16.70 × 5.96mm — confirm against your existing cell before fitting.

• EV-128MRS fit: This cell matches the voltage rail and physical envelope of the original Evolution EV-128MRS battery. The 1.2V nominal output keeps the audio amplifier and display within their operating range across the full discharge curve.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the EV-128MRS platform and confirmed the protection circuit responds correctly to end-of-charge cutoff. No thermal event was observed across multiple charge cycles.
• Post-install charge cycle on the EV-128MRS: After fitting this cell, place the player on charge for a full cycle before first use. Media players can enter deep discharge protection after extended storage, and the device may not accept normal charge current until a slow trickle brings the cell voltage above the threshold — typically around 1.0V per cell.

Battery percentage jumping after cell swap on the EV-128MRS

The EV-128MRS reads battery level by tracking voltage thresholds, not a fuel gauge IC. A fresh Ni-MH cell has a flatter discharge curve than a worn original, so the indicator recalibrates over the first few charge cycles. Expect the displayed percentage to jump or read inaccurately for two to three full charge-discharge cycles. Run the battery down to auto-shutoff and then charge fully each time — the indicator stabilises once the device maps the new cell's voltage profile.

Playback cutting out before the battery indicator shows empty

The audio amplifier in the EV-128MRS draws a higher current burst during playback than the display circuit does at rest. At the end of a Ni-MH discharge curve, cell voltage sags under that load even when the resting voltage still reads as partial charge. The result is audio dropout or sudden shutdown while the battery indicator still shows one or two bars. If this happens, connect the charger immediately — the resting cell voltage at that point is typically at or below 1.05V, which is the amplifier's lower operating limit.