Logitech NTA2479 Pure-Fi Anywhere Speaker 1st Replacement Battery 3.7V 3000mAh

Logitech Pure-Fi Anywhere 1st Gen / MM50 — 3.7V Li-ion Replacement Battery (NTA2479)

This is a 3.7V, 3000mAh Li-ion cell built to the NTA2479 spec, fitting the Logitech Pure-Fi Anywhere Speaker 1st generation and MM50. Both models share the same battery bay, connector, and BMS handshake. Swap it in when the original cell no longer holds a charge or the speaker won't power on.

• Pure-Fi Anywhere 1st Gen and MM50 fit: These two models use the same 3.7V single-cell pack with identical connector orientation and BMS communication lines. One replacement covers both platforms without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the Pure-Fi Anywhere platform. The BMS accepted the cell without fault codes, balanced correctly at 4.2V, and cut off cleanly at the low-voltage threshold without triggering false empty readings.
• Monthly full-discharge cycle: These speakers often sit on a desk and get plugged in before the battery drops below 50%. That shallow cycling causes fuel gauge drift over time. Run the speaker down below 20% at least once a month before recharging to keep the charge indicator accurate.

Audio distortion before the battery indicator reaches empty

As the cell voltage sags under amplifier load, the Pure-Fi Anywhere's amp stage clips before the BMS triggers a low-battery warning. The speaker sounds distorted or crackly while the LED still shows charge remaining. This happens because the fuel gauge reads resting voltage, not loaded voltage — the two diverge when the cell ages or has accumulated shallow cycles. If distortion starts appearing consistently at around 30–40% indicated charge, the cell is no longer holding its voltage under load and needs replacement.

Speaker won't wake from USB after sitting unused for weeks

Leave a lithium-ion cell discharged long enough and it drops below the USB charging circuit's minimum acceptance voltage — typically around 2.5V for this cell chemistry. When that happens, the charger sees the pack as invalid and won't initiate a charge cycle. If the speaker is completely unresponsive on USB, connect it to a wall adapter rather than a computer port, which delivers a consistent 5V and is more likely to trigger the pre-charge trickle mode. Hold the charge for at least 15 minutes before attempting to power on.