DOCKIN D Fine 11.1V Replacement Battery 2600mAh Li-ion

DOCKIN D Fine Series — 11.1V Li-ion Replacement Battery (INR18650-3S1P)

This is an 11.1V 2600mAh Li-ion replacement battery for the DOCKIN D Fine, D Fine 2, and D Fine+ 2 portable Bluetooth speakers. It replaces the original INR18650-3S1P pack when the internal cell has degraded or the speaker no longer holds a charge. Capacity listed here comes directly from the product specification — 2600mAh, 28.86Wh.

• D Fine series compatibility: The D Fine, D Fine 2, and D Fine+ 2 share the same internal battery bay dimensions and the same 11.1V three-cell series configuration. The BMS connector and voltage rail are unchanged across that model run, so one replacement pack covers all three variants.
• Bench tested on actual hardware: We ran this pack through charge and discharge cycles on the D Fine platform. The BMS negotiated correctly at every state of charge, with no false low-battery cutoffs and no unexpected shutdowns during sustained audio output at high amplifier load.
• Monthly discharge cycling on desk-use speakers: If the D Fine lives on a desk and gets topped off constantly, discharge it below 20% at least once a month before recharging. Constant shallow cycling causes fuel gauge drift on the Li-ion cells, and the speaker will start reporting full charge while actual usable capacity quietly drops.

Bluetooth dropping at high volume on the D Fine after battery replacement

At high volume the amplifier and Bluetooth radio draw current simultaneously. On a degraded or mismatched cell, that combined spike causes a voltage sag the BMS reads as an unsafe undervoltage event, and it disconnects the load. The result looks like a Bluetooth dropout but it's actually a brief pack cutoff. A correctly rated 11.1V 2600mAh cell with a healthy internal resistance holds the voltage rail stable through those peaks. If dropouts still occur after fitting a fresh pack, check that the connector is fully seated — a loose contact adds resistance exactly where the current spike happens.

Audio distorting well before the battery indicator reaches empty

This is amplifier clipping under voltage sag, not a speaker fault. As cell capacity degrades, internal resistance rises and the pack voltage drops faster under load — the amplifier hits its minimum supply voltage before the fuel gauge catches up. The indicator still shows bars while the audio breaks up because the gauge is tracking average voltage, not instantaneous sag under load. Fitting a fresh cell restores the voltage headroom. After installation, run one full charge to 100% before the first extended play session so the BMS can calibrate the gauge to the new cell's actual capacity.