CP-HK03 Harman/Kardon Esquire 2 Compatible Battery 3.7V 2800mAh

Harman/Kardon Esquire 2 — 3.7V Li-Polymer Replacement Battery (CP-HK03)

This 3.7V 2800mAh lithium-polymer cell replaces the original CP-HK03 battery in the Harman/Kardon Esquire 2 portable Bluetooth speaker. It matches the OEM dimensions at 67.86 × 48.10 × 7.00mm and fits the existing connector and housing without modification. Swap it when the original pack no longer holds a charge or causes audio to cut out before the indicator reads empty.

• Esquire 2 fitment: The Esquire 2 uses a flat Li-Polymer pouch cell with a specific footprint and connector pinout tied to its fuel gauge IC. This cell matches those dimensions and connector orientation, so the BMS can read state-of-charge correctly through the same communication line the original used.
• Bench tested on actual hardware: We ran the pack through charge and full-discharge cycles on an Esquire 2 unit. The BMS accepted the cell without error flags, the fuel gauge tracked accurately across the range, and the amplifier maintained clean output under combined Bluetooth and high-volume draw.
• Monthly full-discharge cycle for Esquire 2 users: The Esquire 2 spends most of its life on a desk, topped off constantly. Let the speaker play down below 20% at least once a month before plugging it back in — the fuel gauge IC recalibrates on a full cycle, and skipping this accelerates capacity fade on the pouch cell.

Audio distorting before the battery indicator reaches empty on the Esquire 2

The Esquire 2's Class D amplifier draws sharp current spikes at high volume. When the cell ages and internal resistance rises, those spikes cause voltage sag below the amplifier's clean-operating threshold before the fuel gauge registers critical. The result is audible distortion and clipping while the LED still shows charge remaining. Fitting a fresh cell with lower internal resistance eliminates the sag — confirm the pack is at or above 3.7V resting voltage before the first charge cycle.

Esquire 2 not waking from USB when battery is deeply discharged

If the speaker sat unused for several months, the cell may have self-discharged below the USB acceptance threshold — typically around 2.5V for Li-Polymer. The charger controller won't initiate a standard charge handshake below that floor, so the speaker appears completely dead on USB. Connect it to a 5V USB-A source rather than USB-C PD, which can be more forgiving during trickle pre-charge recovery. Leave it connected for 20–30 minutes before attempting to power on; the BMS needs to confirm the cell is above 2.8V before enabling the main charge path.