About this replacement
JBL Pulse 4 — 3.7V Li-ion Replacement Battery (SUN-INTE-168)
This 3.7V, 10200mAh Li-ion battery replaces the original cell in the JBL Pulse 4 portable Bluetooth speaker. It fits the Pulse 4's internal battery bay and works with the speaker's onboard charging and protection circuit. Capacity figure is 10200mAh — use this number, not third-party listings that vary.
- Pulse 4 fitment: The Pulse 4 uses a single large-format Li-ion cell to power both the amplifier stage and the LED ring simultaneously. That combined draw is higher than most speakers of the same size, so cell capacity and discharge rate both matter here.
- Bench tested on actual hardware: We ran this cell through the Pulse 4's BMS handshake at full LED and audio load. The protection circuit accepted the pack without fault codes, and charge termination fired correctly at 4.2V.
- Fuel gauge reset after install: The Pulse 4 tracks charge state through its BMS, not a separate gas gauge IC. After fitting a new cell, run the speaker down until it shuts off automatically, then charge it uninterrupted to 100%. This recalibrates the charge indicator — skipping it causes the battery bar to misread from day one.
Why the Pulse 4 cuts out when the LED ring is at full brightness
The Pulse 4 drives its LED array and Class D amplifier from the same cell. At maximum LED brightness combined with loud playback, instantaneous current draw spikes sharply. A degraded or undersized cell can't sustain that draw without the terminal voltage dropping below the BMS cutoff threshold. The speaker then shuts off to protect the cell — even if the charge indicator still shows bars. A fresh 10200mAh cell with adequate discharge headroom handles the combined load without triggering the cutoff.
Audio distortion before the battery indicator reaches empty
This happens when the cell voltage sags under amplifier load before the BMS registers a low-battery condition. The amplifier clips because its supply rail drops below the voltage it needs to reproduce the signal cleanly — the battery indicator hasn't caught up yet. It's not a speaker fault; it's voltage sag from a worn cell that can't hold terminal voltage under dynamic load. Replacing the cell and running a full discharge-to-shutoff cycle, then a full recharge, resets the fuel gauge and eliminates false readings.