About this replacement
Altec Lansing IMW888 / IMW889 Series — 11.1V Li-ion Replacement Battery (INR18650-3S)
This is an 11.1V, 2600mAh (28.86Wh) Li-ion battery pack for the Altec Lansing IMW888-BLG, IMW888S, IMW889N-BLKC, IMW889, and related waterproof Bluetooth speaker models. It replaces the original INR18650-3S three-cell pack that powers the speaker's amplifier, Bluetooth radio, and DSP board. When the original pack degrades and no longer holds a usable charge, this unit restores full portable operation.
- IMW888 and IMW889 platform fit: Both series run the same 11.1V three-cell architecture with an identical connector pinout and BMS handshake protocol. The shared power rail means one pack covers the IMW888-BLG, IMW888S, IMW889N-BLKC, and IMW889 without any wiring modification.
- Bench tested on actual hardware: We cycled this pack through charge and discharge on the IMW888 platform. The BMS held cutoff voltage correctly at cell-level, and the protection circuit responded to overcurrent conditions at the amplifier draw spike without nuisance tripping during normal playback.
- Fuel gauge calibration on the IMW888: Let the speaker discharge below 15% at least once a month before recharging. Constant top-off charging without a full discharge cycle causes the onboard fuel gauge to drift — the speaker will report full charge and shut down unexpectedly well before the cells are actually depleted.
Audio distorting before the battery indicator reaches empty on the IMW888
As Li-ion cells age, internal resistance rises. Under amplifier load — especially at high volume — the pack voltage sags faster than the indicator circuit can track. The amplifier hits its minimum supply voltage and starts clipping before the fuel gauge shows a low-battery warning. Fitting a fresh 2600mAh pack with lower internal resistance restores the voltage headroom the amplifier needs at full output. If distortion appears immediately after fitting the new battery, charge the pack to full first — voltage on arrival may be below the 11.1V nominal rail.
Bluetooth dropping specifically at high volume — not at low volume
The IMW888 amplifier and Bluetooth radio share the same battery rail. At high volume, the amplifier pulls a sharp current spike that momentarily sags the pack voltage. If the battery's BMS or the cells themselves can't respond fast enough, the radio module browns out and drops its connection. This is distinct from a range or interference problem — it only happens under combined amp and radio draw, and it clears at lower volume. Confirm the battery is fully charged to 12.6V before testing; a partially charged pack has less headroom for current spikes and will exhibit this symptom even if the cells are otherwise healthy.