Sony WH-1000XM5 Replacement Battery 3.8V 1200mAh SP723741

Sony WH-1000XM5 — 3.8V Li-Polymer Replacement Battery (SP723741)

This 3.8V, 1200mAh Li-Polymer cell replaces the original SP723741 battery inside the Sony WH-1000XM5 wireless noise-cancelling headphones. It fits the WH-1000XM5 and WF-1000XM5 models. Capacity is 4.56Wh — matching the factory specification from the product data.

• WH-1000XM5 and WF-1000XM5 compatibility: Both models use the same SP723741 cell format, voltage rail, and connector footprint. The BMS on each headset communicates directly with this cell's protection circuit, so charge termination and low-voltage cutoff behave exactly as they do with the factory pack.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the WH-1000XM5 platform. The BMS accepted the new pack without error flags, and the protection circuit triggered at the expected low-voltage threshold with no false cutoffs during audio plus ANC combined draw.
• First-cycle charge on the WH-1000XM5: After fitting the new cell, run one complete charge through the headset's USB-C port before use. The onboard fuel gauge resets its capacity estimate during that first full cycle — skipping it leaves the battery indicator inaccurate for the first several sessions.

Why the WH-1000XM5 cuts out mid-listening on a new battery

The WH-1000XM5 draws current from two systems at once: the audio amplifier and the active noise cancellation processor. Under peak ANC load combined with high-volume output, instantaneous current demand spikes sharply. If the cell's protection circuit is set conservatively — common in a freshly installed pack — it can interpret that spike as an overcurrent event and trip the BMS. After two or three full charge-discharge cycles, the protection circuit settles and the cutoffs stop. If the problem persists beyond five cycles, check that the replacement cell is seated flush and the connector is fully latched.

Headset shows full charge but cuts off after a few tracks

This happens when the new cell arrives at storage voltage — typically around 3.6V — and the fuel gauge hasn't yet mapped actual cell capacity. The headset reads a surface voltage, reports full, then hits the low-voltage cutoff quickly once current flows. One complete charge from near-empty to 100% via USB-C gives the BMS enough data to calibrate the state-of-charge curve. After that cycle, reported charge levels will track actual capacity correctly.