About this replacement
Soundcast ICO420 / ICO421 — 24V Ni-MH Replacement Battery (2-540-001-01)
This is a 24V, 2000mAh (48Wh) Ni-MH replacement battery for the Soundcast ICO420 and ICO421 portable Bluetooth speakers. It replaces OEM part numbers 2-540-001-01, ICOB2, and OUTCAST 20S-1P. Fit also covers units sold under the Outcast ICO420 and Outcast ICO421 names.
- ICO420 and ICO421 platform compatibility: Both the ICO420 and ICO421 share the same 24V battery rail, connector pinout, and BMS handshake protocol — one pack covers both units without modification.
- Bench tested on actual hardware: We cycled this pack through full charge and discharge runs on the ICO420. The BMS held steady at 24V nominal, protection circuitry tripped correctly at low-cell threshold, and the speaker's charge indicator tracked accurately throughout.
- Ni-MH discharge cycle tip: Ni-MH cells in the ICO420 are susceptible to voltage depression from repeated shallow discharges. Run the speaker down to near-empty at least once a month before recharging — this keeps the cell voltage curves balanced and prevents the fuel gauge from reading full when actual capacity has dropped.
Why the ICO420 reads full charge but audio cuts out after an hour
Ni-MH cells develop voltage depression after months of partial-discharge cycling — the pack appears full on the indicator but actual deliverable capacity is a fraction of the rated 2000mAh. The BMS reads voltage, not true stored charge, so it reports full even when the cells are degraded. A replacement pack restores the full 48Wh capacity the amplifier circuit expects. After fitting this battery, run one complete discharge before topping off to let the BMS recalibrate its voltage-to-capacity mapping.
Bluetooth signal dropping at high volume on a freshly charged pack
At high volume the ICO420's amplifier and Bluetooth radio draw simultaneously, creating current spikes that cause momentary voltage sag across the pack. On a degraded original battery, internal resistance is high enough that these spikes pull cell voltage below the radio module's minimum operating threshold, dropping the Bluetooth link. This replacement pack has lower internal resistance at 24V, keeping the voltage rail stable under combined amp and radio load. If dropouts persist after fitting, check that the battery connector is fully seated — a loose connection adds resistance and recreates the same sag.