About this replacement
Braven 405 — 3.7V Li-Polymer Replacement Battery (GSP103465)
This is a 3.7V, 1900mAh Li-Polymer cell replacing the original GSP103465 pack in the Braven 405 portable Bluetooth speaker. It fits the compact 405 chassis directly, restoring cordless audio playback and Bluetooth functionality. Capacity figure is sourced from the product data, not estimated.
- Braven 405 fitment: The 405 uses a slim Li-Polymer cell at 71.30 x 39.40 x 6.10mm — a tight envelope shared by no other Braven model in this series. Connector orientation and BMS communication are matched to the 405 motherboard, so the fuel gauge reads correctly from first charge.
- Bench tested on actual hardware: We cycled this cell through the 405 charge circuit and confirmed the BMS accepted the pack without fault flags. Audio output held steady across the draw range from low-volume streaming to max amplifier output.
- Monthly discharge cycle for the 405: The 405 sits on desks and gets topped off constantly — that shallow cycling pattern drifts the fuel gauge and accelerates cell degradation. Run the speaker down below 20% at least once a month before plugging in, to keep the gauge calibrated and the cell cycling through its full capacity range.
Braven 405 showing full charge but audio cuts out after extended play
A worn cell loses usable capacity but the fuel gauge still reports high charge because it was calibrated on the original cell's cycle history. The 405 amplifier draws a combined load with the Bluetooth radio — under that combined pull, a degraded cell sags below the BMS cutoff threshold faster than the indicator reflects. The speaker shuts off not because the battery is physically empty, but because cell voltage dropped below the BMS floor under load. Replacing the cell and running one full discharge cycle resets the gauge baseline.
Audio distorting at high volume before the battery indicator reaches empty
This is amplifier clipping driven by voltage sag, not a speaker fault. At high volume, the 405 amplifier pulls a current spike that the cell can't sustain cleanly — voltage dips momentarily, and the amplifier clips the waveform on the low rail. The distortion appears well before the battery indicator shows critical because the average voltage reads acceptable while instantaneous sag is already too deep. A fresh cell with lower internal resistance holds the voltage rail steady under those spikes — check that the replacement cell measures above 3.7V at rest before first charge.