Harman/Kardon GO + Play 3 Compatible Battery 10.8V 3500mAh

Harman/Kardon GO + Play 3 — 10.8V Li-ion Replacement Battery (C1146B-18650-3S1P)

This is a 10.8V, 3500mAh Li-ion replacement battery for the Harman/Kardon GO + Play 3 portable Bluetooth speaker. It replaces OEM part numbers C1146B-18650-3S1P and GSP102910201. The cell arrangement is a 3S1P 18650 configuration — three cells in series to hit the 10.8V rail the GO + Play 3 amplifier requires.

• GO + Play 3 fit: The GO + Play 3 uses a dedicated battery bay with a specific connector keyed to its amplifier and BMS handshake circuit. This battery matches that connector pinout, voltage rail, and communication protocol — the speaker's protection board reads cell state correctly on first boot.
• Bench tested on actual hardware: We ran this pack through charge and discharge cycles on the GO + Play 3 platform. The BMS flagged no fault codes, the charge LED sequence completed normally, and the fuel gauge reported accurate state-of-charge throughout the test.
• Fuel gauge reset after install: After fitting this battery, run the speaker down until it shuts off automatically, then charge it uninterrupted to 100%. The GO + Play 3 fuel gauge calibrates on a full discharge-to-charge cycle — skipping this step causes the indicator to read full when actual capacity is lower.

Why the GO + Play 3 audio cuts out before the battery indicator hits empty

The GO + Play 3 amplifier draws a sharp current spike at high volume. When the Li-ion cells age and internal resistance rises, that spike causes a momentary voltage sag below the amplifier's minimum operating threshold — even if the fuel gauge still shows charge remaining. The speaker reads this sag as a fault and shuts audio output to protect the circuit. A fresh cell pack with lower internal resistance handles the same current spike without the sag, and the cutout stops.

GO + Play 3 won't wake from USB-C after sitting unused for months

If the speaker sits uncharged for an extended period, the cells can drop below the USB-C Power Delivery minimum acceptance voltage — typically around 2.5V per cell, or roughly 7.5V across the 3S pack. At that point the charger handshake fails and the speaker appears completely dead. Connect it to a 5V USB-A charger instead of USB-C first — the lower-voltage trickle path can bring the cells back above the PD acceptance threshold. Once the pack reads above approximately 9V, switch to the standard USB-C charger to complete the charge cycle.