Monster Ncredible Ntune Replacement Battery 3.7V 400mAh

Monster Ncredible Ntune / Ncredible 1 — 3.7V Li-Polymer Replacement Battery (SC-EP-N0020-U)

This is a 3.7V, 400mAh Li-Polymer replacement battery for the Monster Ncredible Ntune and Ncredible 1 wireless headphones. It restores power to the onboard audio circuit and Bluetooth radio when the original cell no longer holds a usable charge. Dimensions are 37.00 × 30.00 × 5.12mm — measure your existing cell before ordering.

• Ncredible Ntune and Ncredible 1 compatibility: Both headphones run the same 3.7V cell with an identical footprint and connector orientation. The BMS in each headset accepts this cell without modification or firmware changes.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the Ncredible platform. The protection circuit held cutoff at the correct low-voltage threshold and accepted a full charge without triggering an overcurrent fault.
• First-cycle charging on the Ncredible: After fitting a new cell, run a complete charge-to-full cycle before extended use. The headset's charge indicator calibrates against the new cell's actual capacity on that first cycle — skipping it causes the LED to misread remaining charge on early uses.

Why the Ncredible Ntune cuts out mid-track on a new battery

The Ncredible Ntune draws from a single small cell powering both the audio amplifier and the Bluetooth radio simultaneously. At high volume, the combined current spike can exceed 400mA momentarily. If the replacement cell has not completed a full conditioning cycle, internal resistance stays elevated and voltage sags enough to trigger the low-voltage cutoff, shutting the headset off. After two to three full charge-discharge cycles, internal resistance drops and the cutoff trips less frequently.

Charge LED shows full but headset goes silent after a few songs

A new cell ships at storage voltage — typically around 3.6V — not a full charge. The headset's charge circuit can interpret this as near-full and stop charging early on the first attempt, showing a full indicator. The cell is not actually at 4.2V and cannot sustain the draw. Plug the headset in for a complete uninterrupted charge until the LED confirms full, then use it until it cuts off naturally — that one full cycle resets the gauge.