About this replacement
JBL Charge 4 Series — 3.7V Li-ion Replacement Battery (ID998)
This is a 3.7V, 10200mAh Li-ion replacement battery for the JBL Charge 4, Charge 4J, and Charge 4BLK portable Bluetooth speakers. It slots into the same position as the original cell and connects to the same BMS board. Use this when the original pack no longer holds a full charge or causes unexpected shutdowns during playback.
- Charge 4 and 4J compatibility: All variants in this lineup — JBLCHARGE4BLUAM, Charge 4BLK, Charge 4J — share the same battery bay dimensions (66.30 × 38.50 × 36.30mm), voltage rail, and connector pinout. The BMS handshake is identical across the range, so one SKU covers all four models without modification.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a Charge 4 unit. The BMS accepted the pack without fault codes, balanced across the protection circuit correctly, and the fuel gauge reported accurately through the speaker's LED indicator strip.
- Monthly discharge cycle for the Charge 4: The Charge 4 is typically used as a desk or countertop speaker and topped off constantly. Let the cell drop below 20% at least once a month before recharging. Continuous shallow cycling without a full discharge causes fuel gauge drift and accelerates capacity fade on the Li-ion cell faster than deep-cycle use would.
Voltage sag under combined amplifier and Bluetooth radio draw
At high volume, the Charge 4 amplifier pulls a sharp current spike at the same time the Bluetooth radio is transmitting. A degraded or partially discharged cell cannot sustain voltage under that combined load. The BMS interprets the sag as a low-cell event and reduces output before the indicator shows empty. A fresh 10200mAh cell at full charge holds the voltage rail stable through those peaks without triggering early cutoff.
Speaker not waking from USB-C charge after sitting unused for weeks
If the Charge 4 sits uncharged for an extended period, the cell can drop below the minimum acceptance voltage for USB-C Power Delivery — typically under 2.5V per cell. At that point the charger handshake fails and the speaker shows no response. Connect the original JBL USB-C cable, hold the power button for 10 seconds while plugged in, then leave it connected for at least 30 minutes before attempting a normal power-on. This nudges the BMS into pre-charge mode and lets the cell recover to a level where standard charging resumes.