iRiver Clix Plus M1-F1228C-C Replacement Battery 3.7V 950mAh

iRiver Clix Plus / U20 — 3.7V Li-Polymer Replacement Battery (M1-F1228C-C)

This is a 3.7V, 950mAh Li-Polymer replacement battery for the iRiver Clix Plus and U20 portable media players. It fits a compact 51.58 × 36.31 × 3.06mm cell footprint inside the original housing. If your Clix Plus no longer holds a charge or won't power on after storage, this cell replaces the degraded original.

• Clix Plus and U20 compatibility: Both devices share the same cell format, connector pinout, and voltage rail. The Clix Plus and U20 also appear under the retail model codes REI-iriverclix1 and REI-iriverclix2 — all use the same M1-F1228C-C cell.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the Clix Plus platform. The onboard protection circuit responded correctly to charge cutoff at 4.2V and discharge cutoff near 3.0V with no tripping anomalies.
• First charge after a swap: After installing, charge the device fully before first use. Media players that have sat unused often enter a deep discharge protection state. The cell needs a slow trickle charge before the device accepts normal charge current — skipping this step can leave the indicator stuck at zero.

Battery percentage jumping after a cell swap on the Clix Plus

The Clix Plus uses a voltage-threshold fuel gauge — it reads cell voltage and maps it to percentage steps. After a new cell goes in, the firmware's stored reference points no longer match the new cell's discharge curve. The indicator may jump from 80% to 20% mid-session or report full charge immediately after a short charge. Run two full charge-to-cutoff cycles and the gauge recalibrates to the new cell's actual voltage profile.

Playback cutting out before the battery indicator shows empty

The audio amplifier inside the Clix Plus draws a surge of current at the end of the discharge curve, when cell voltage is already low. A degraded or deeply discharged cell cannot sustain that load — voltage sags below the device's minimum operating threshold and the player shuts off, even though the indicator hasn't reached zero. This is a cell voltage issue, not a firmware bug. A fresh cell at 950mAh capacity holds voltage stable through that final draw phase — confirm the replacement cell is fully charged to 4.2V before testing.