About this replacement
Sony SRS-X30 / SRS-XB30 Series — 7.4V Li-ion Replacement Battery (ID659)
This is a 7.4V, 6800mAh (50.32Wh) Li-ion replacement battery for the Sony SRS-X30, SRS-XB3, SRS-XB30, and SRS-XB43 portable Bluetooth speakers. It slots into the same housing as the original pack and connects to the same BMS interface. Capacity figures come from the product data, not estimates.
- SRS-X30 / XB3 / XB30 / XB43 platform fit: These four models share the same internal battery bay, connector pinout, and BMS communication protocol — which is why a single cell replacement covers all four. The 7.4V nominal rail feeds both the Class D amplifier and the Bluetooth radio from a common battery bus.
- Bench tested on actual hardware: We ran this pack through charge and discharge cycles on the SRS-XB30. The BMS handshake completed on first connection, fuel gauge calibrated correctly by the second full cycle, and the protection circuit tripped cleanly at the low-voltage cutoff threshold without nuisance shutdowns.
- Monthly discharge cycle for SRS series speakers: If this speaker sits on a desk and gets topped off before it drops below 50%, the fuel gauge will drift within a few months. Let the speaker play down past 20% at least once a month before recharging — this keeps the Li-ion cell's state-of-charge estimate accurate and slows capacity fade.
Audio distortion before the battery indicator reaches empty on the SRS-XB30
As a Li-ion cell ages, its internal resistance rises. Under the combined current draw of the amplifier and Bluetooth radio at high volume, terminal voltage sags faster than the fuel gauge expects. The amplifier hits its minimum supply voltage and starts clipping the audio signal — this shows up as crackling or thinning bass — while the battery indicator still reads one or two bars. A fresh cell at 6800mAh has lower internal resistance, which reduces the sag under load and pushes that clipping threshold further down the discharge curve.
Speaker shows full charge but audio cuts out after extended play
This is fuel gauge drift, not a faulty charge circuit. Years of shallow top-off charging — never completing a full discharge — cause the BMS to lose accurate track of the cell's actual capacity. It reports "full" based on voltage alone, but the usable window has shrunk. After fitting this replacement pack, run two full discharge-to-recharge cycles before trusting the indicator. By the end of the second cycle the BMS recalibrates against the cell's real capacity and the gauge reads accurately again.