Sony SRS-XB501 Replacement Battery 7.4V 5200mAh ID659B

Sony SRS-XB501 / SRS-XB501G — 7.4V Li-ion Replacement Battery (ID659B)

This is a 7.4V, 5200mAh (38.48Wh) Li-ion replacement battery for the Sony SRS-XB501 and SRS-XB501G portable Bluetooth speakers. It matches the OEM part number ID659B and fits the original battery bay directly. If your speaker no longer holds a charge or shuts down during playback, this swap restores full operating voltage to the audio and Bluetooth amplifier circuits.

• SRS-XB501 and SRS-XB501G compatibility: Both variants run the same 7.4V power rail, use the same connector pinout, and communicate with the same BMS. One battery covers both model suffixes without any hardware modification.
• Bench tested on actual hardware: We ran the ID659B replacement through full charge and discharge cycles on the SRS-XB501 platform. The BMS handshake cleared on first connection — no fault codes, no charge refusal. Cell voltage held stable across the amplifier's peak current draw at high volume output.
• Fuel gauge calibration for the SRS-XB501: Let the battery discharge below 20% at least once a month before recharging. The SRS-XB501 is typically kept topped off near a desk or bag, which causes fuel gauge drift over time. Skipping occasional deeper cycles makes the indicator read inaccurately before the cell actually empties.

Why the SRS-XB501 cuts out at high volume even on a full charge

At maximum volume, the SRS-XB501's amplifier pulls a sharp current spike that can exceed what a degraded cell will deliver without sagging below the BMS cutoff threshold. The protection circuit reads the voltage dip as a fault condition and interrupts output to avoid cell damage. A fresh cell with low internal resistance handles the transient load without tripping. If drop-outs only happen above 70% volume, internal resistance on the old cell is the cause — not the BMS configuration.

Speaker won't wake from USB charge after sitting unused for weeks

Li-ion cells left in deep discharge drop below the minimum acceptance voltage for USB-C PD negotiation — typically under 2.5V per cell on a 7.4V pack. At that level, the charger handshake fails and the speaker appears completely dead. Plug into a USB port rather than a wall adapter first — lower initial current lets the BMS recover the cell incrementally. Once the pack reaches approximately 3.0V per cell, standard charging resumes and the speaker powers on normally.