About this replacement
JBL Charge 5 — 3.7V Li-ion Replacement Battery (GSP-1S3P-CH4A)
This 3.7V Li-ion battery replaces the factory cell in the JBL Charge 5 portable Bluetooth speaker. It also fits the Charge 4 using part number GSP-1S3P-CH4A. Capacity is 7800mAh (28.86Wh), matching the original cell specification.
- Charge 4 and Charge 5 compatibility: Both speakers share the same cell footprint and connector orientation. The GSP-1S3P-CH4A part number covers both generations. The BMS handshake protocol and voltage rail are identical across these two models, so no firmware mismatch occurs on install.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a Charge 5 unit. The BMS accepted the pack without error flags, balanced the cells correctly, and the speaker's LED fuel gauge reported accurately across the full voltage range.
- Fuel gauge calibration tip: If you use this speaker on a desk and top it off constantly, let it discharge below 20% at least once a month before reconnecting the charger. Constant shallow cycling causes fuel gauge drift — the indicator will show full charge while actual capacity quietly erodes.
Audio distorting before the battery indicator reaches empty
The Charge 5 amplifier draws a sharp current spike at high volume. When the cell voltage sags under that combined amplifier and radio load, the amp clips before the battery indicator triggers its low-charge warning. The indicator reads the resting voltage, not the loaded voltage under peak draw. If you hear distortion while the gauge still shows one or two bars, check that the cell is above 3.5V under load — a healthy cell at this capacity holds that rail without sag.
Speaker won't respond to USB-C charging after sitting unused for months
A deeply discharged Li-ion cell can fall below the USB-C Power Delivery minimum acceptance voltage — typically around 2.5V per cell. At that point the speaker's charging circuit doesn't negotiate a PD handshake and nothing happens when you plug in. Connect the speaker to a 5V USB-A charger instead of a USB-C PD source first; the lower-current path can tickle the BMS back into accepting charge. Once the cell reaches roughly 3.0V, switch to the standard USB-C cable and charge normally.