GJ802540 JBL Wind Replacement Battery 3.7V 800mAh

JBL Wind — 3.7V Li-Polymer Replacement Battery (GJ802540)

This is a 3.7V, 800mAh Li-Polymer replacement battery for the JBL Wind portable Bluetooth speaker. Part number GJ802540 matches the original cell geometry at 42.50 × 31.20 × 6.00mm. It restores power to a Wind unit where the original cell no longer holds a full charge.

• JBL Wind fit: The Wind shares a single-cell Li-Polymer architecture with a tight housing — voltage rail sits at 3.7V nominal, and the BMS handshake is keyed to that cell profile. Swapping in a mismatched cell trips the protection circuit and prevents charging entirely.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the Wind platform. The BMS accepted the cell without flagging a fault, charge termination occurred correctly at 4.2V, and undervoltage cutoff triggered at the expected threshold.
• Fuel gauge calibration on the Wind: Let the speaker discharge below 20% at least once a month before recharging. The Wind's fuel gauge drifts when the cell is constantly topped off from 60–70%, causing the indicator to read full while actual capacity has dropped significantly.

Portable speaker showing full charge but audio drops after an hour

This happens when the cell has lost usable capacity through shallow cycling but the fuel gauge still reports 100%. The BMS reads voltage, not true state of charge — so a degraded cell appears full until it sags under amplifier load. Once voltage drops below the BMS cutoff threshold, the speaker shuts down abruptly. Replacing the cell and running two full discharge-to-recharge cycles resets the gauge baseline.

JBL Wind USB charging not starting after the battery ran fully flat

When a Li-Polymer cell discharges below roughly 2.5V, the BMS locks the charge path to prevent damage. USB-C PD negotiation cannot begin because the charger sees a pack voltage below its minimum acceptance threshold. Most chargers simply show no charging activity and draw no current. Connect to a charger capable of trickle or pre-charge mode and leave it for 15–20 minutes — once the cell climbs above 2.8V, the BMS releases the charge path and normal charging resumes.