Sony NP-BJ1 RXO Replacement Battery 3.7V 700mAh

Sony RXO / DSC-RX0 Series — 3.7V Li-ion Replacement Battery (NP-BJ1)

This is a 3.7V, 700mAh Li-ion replacement cell built to the NP-BJ1 specification. It fits the Sony RXO, RX0, RX0 Ultra, and DSC-RX0 compact action cameras. Slot it in where the original sits — same footprint at 39.60 × 31.15 × 6.10mm.

• RXO series compatibility: These models share the same NP-BJ1 battery slot, voltage rail, and BMS handshake. The connector orientation and physical housing are identical across the RXO, RX0, and RX0 Ultra, so one replacement cell covers the full lineup.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on RXO hardware. The BMS accepted the cell, reported charge state correctly, and did not trigger low-voltage cutoff prematurely at the 3.7V nominal rail.
• First-use charge cycle on RXO bodies: Insert the cell and charge it fully inside the camera body or via the OEM charger before your first shoot. Sony's BMS on the RXO maps battery-remaining display to a charge profile it builds on the first full cycle — skipping this step can produce inaccurate percentage readings from the start.

Why the RXO drains its cell faster under 4K video than stills shooting

The DSC-RX0 runs a 1-inch stacked CMOS sensor alongside continuous image processing when recording 4K. That combined draw — sensor readout, processor load, and constant write to card — pulls significantly more current than single-frame stills capture. At 700mAh, the NP-BJ1 is a small cell by design; the camera body is built for compactness, not extended recording. Keep a second cell charged when shooting video, because the draw differential between stills and continuous 4K is substantial on this platform.

Battery percentage jumping or dropping suddenly on the RXO display

If the remaining battery indicator skips — say, from 60% to 20% without warning — the camera's voltage-threshold map hasn't calibrated to the new cell's discharge curve. This happens because the BMS built its reference table on the original cell over many cycles. Run one full charge-to-discharge cycle without interruption to let the BMS re-map thresholds to the replacement cell. After that cycle, the display should track steadily from 100% down to the low-voltage cutoff near 3.0V.