About this replacement
JBL Partybox Encore Essential — 3.7V Li-ion Replacement Battery (GSP-1S2P-F5A)
This 3.7V 6800mAh Li-ion battery replaces the GSP-1S2P-F5A cell inside the JBL Partybox Encore Essential portable speaker. It restores power when the original pack no longer holds adequate charge. Voltage and capacity match the factory spec exactly — 3.7V, 6800mAh (25.16Wh).
- Partybox Encore Essential compatibility: The Encore Essential runs a single-cell 1S2P Li-ion configuration tied to its onboard charging and protection circuit. This pack matches that rail and connector, so the BMS handshake completes without triggering a fault code on the speaker's charge controller.
- Bench tested on actual hardware: We cycled this pack through charge and discharge on the Encore Essential platform. The BMS handled both the amplifier draw at high volume and the simultaneous Bluetooth radio current without tripping an undervoltage cutoff.
- Monthly discharge cycle on the Encore Essential: Let the speaker run below 20% at least once a month before plugging in. The Encore Essential is frequently kept on a desk and topped off constantly — this shallow cycling causes fuel gauge drift and accelerates capacity fade on the Li-ion cell faster than deeper discharge cycles would.
Audio distorting before the battery indicator reaches empty
As the cell discharges past roughly 3.5V, the amplifier inside the Encore Essential begins to clip because the supply voltage can no longer sustain peak output current. The speaker's fuel gauge still shows one bar remaining, but the amp is already starved. This is voltage sag under load — not a sign the battery is faulty. If you hear distortion early in what looks like a partial charge, the cell is likely degraded and holding a surface charge rather than a full 6800mAh. Replacing the pack clears this symptom immediately once the new cell is cycled once.
Speaker won't wake from USB-C after sitting discharged for weeks
Li-ion cells that drop below approximately 2.5V enter a deep-discharge state where most USB-C PD chargers refuse to negotiate power delivery — the charger sees the pack voltage as too low to accept a charge handshake. The Encore Essential will appear completely dead. Connect the speaker to a USB-C charger rated at least 10W and leave it untouched for 20–30 minutes before pressing the power button — most BMS circuits include a trickle pre-charge mode that slowly brings the cell back above the 2.8V threshold needed to resume normal charging. If the indicator light still does not appear after 45 minutes, the original cell has likely degraded past recovery and needs replacement.