Audio-Technica LI-210 Portable Speaker Compatible Battery 3.7V 2600mAh

Audio-Technica AT-SB727 Sound Burger — 3.7V Li-ion Replacement Battery (LI-210)

The LI-210 is a 3.7V, 2600mAh Li-ion cell that powers the Audio-Technica AT-SB727 Sound Burger portable turntable speaker. It replaces the original pack when the unit no longer holds a charge or cuts out during playback. Dimensions are 65.70 × 21.50 × 18.30mm — confirm these against your existing cell before ordering.

• AT-SB727 and AUATSB727 compatibility: Both model designations use the same LI-210 pack. The voltage rail, connector pinout, and BMS handshake are identical across the AT-SB727 and AUATSB727 variants, so one cell fits both.
• Bench tested on actual hardware: We cycled the LI-210 through charge and discharge on the AT-SB727 platform. The BMS held protection thresholds correctly — no false overcurrent trips, no undervoltage cutoff at idle draw, and charge termination landed at the expected 4.2V cell ceiling.
• Monthly discharge cycle for the AT-SB727: This unit gets left on a desk and topped off constantly. That shallow cycling causes fuel gauge drift — the indicator reads full while actual capacity is 60% or less. Run the speaker down below 20% at least once a month before recharging to reset the fuel gauge and slow capacity fade on the Li-ion cell.

Bluetooth dropping at high volume on a new LI-210

At high volume the AT-SB727 amplifier draws a spike of current on top of the constant Bluetooth radio draw. If the cell has any internal resistance — even on a new pack that was shipped in partial-charge state — the combined load causes a momentary voltage sag. The BMS reads that sag as an undervoltage event and briefly cuts the radio before the amp recovers. Charge the LI-210 fully to 4.2V before first use; that sag window narrows significantly on a fully conditioned cell.

Audio distorting before the battery indicator reaches empty

The AT-SB727 amplifier begins clipping when cell voltage drops below roughly 3.5V, even though the indicator may still show one or two bars. The battery gauge uses a voltage-to-capacity curve that can drift after months of shallow cycling, so the display lags behind real cell state. You hear the distortion first — it is not a speaker fault. Swap in a charged LI-210 and confirm voltage at the cell terminals reads 3.7V or above before ruling out the amplifier.