About this replacement
JBL PartyBox 100 — 14.4V Li-ion Replacement Battery (SUN-INTE-260)
This 14.4V 3400mAh (48.96Wh) Li-ion battery replaces the original pack in the JBL PartyBox 100 portable speaker. It restores cordless audio playback when the factory battery has degraded or stopped holding charge. Fits the PartyBox 100 and R21-5 using OEM part references SUN-INTE-260 and DH14026CHM.
- PartyBox 100 and R21-5 compatibility: Both units run the same 14.4V battery rail with the same physical connector and BMS handshake protocol, which is why one cell pack covers both fit models without modification.
- Bench tested on actual hardware: We cycled this pack through charge and discharge on the PartyBox 100 platform. The BMS negotiated correctly with the speaker's protection circuit, holding steady voltage through both high-volume amplifier draw and Bluetooth radio load simultaneously.
- Monthly discharge cycle for PartyBox 100 users: Let the speaker drain below 20% at least once a month before recharging. Constant top-off charging without a full discharge causes fuel gauge drift and accelerates capacity fade on the Li-ion cells — this is especially common with speakers kept plugged in between occasional uses.
Audio distorting before the battery indicator reaches empty on the PartyBox 100
The PartyBox 100 amplifier pulls a hard current spike at high volume. As the battery ages and internal resistance climbs, voltage sags under that load even when the fuel gauge still reads 20–30%. The amplifier hits its minimum rail voltage and clips the audio signal before the protection circuit calls the pack empty. Replacing the battery with a fresh 14.4V cell restores the voltage headroom the amplifier needs to run cleanly at full output.
PartyBox 100 won't wake from USB-C charging after sitting unused for weeks
A deeply discharged Li-ion pack can fall below the USB-C PD minimum acceptance voltage, so the charger handshake never completes and the speaker appears completely dead. The BMS needs a trickle pre-charge to bring the cell back into the PD negotiation window before fast charging kicks in. If the speaker shows no response after 30 minutes on charge, try a different USB-C power adapter rated at least 20W — some lower-wattage adapters lack the pre-charge routine required to recover a deeply discharged pack. If the pack still won't accept charge at all, the cells have likely dropped below the BMS recovery threshold and replacement is the correct fix.