About this replacement
Sony CX405 Handycam & DSC-HX Series — 3.7V Li-ion Replacement Battery (NP-BX1)
This is a 3.7V, 950mAh Li-ion replacement for the Sony NP-BX1 battery. It fits the CX405 Handycam, DSC-HX90V, DSC-HX90V/B, DSC-HX99, and over 100 additional Sony camera and camcorder models sharing the same NP-BX1 footprint. Capacity is 3.52Wh — matched to the original spec.
- Cross-model compatibility on the NP-BX1 platform: Sony spread the NP-BX1 format across compact cameras, camcorders, and action cams because they share the same 3.7V rail, physical connector, and BMS communication protocol. One cell format covers the full range without modification.
- Bench tested on actual hardware: We ran this cell in a CX405 body and a DSC-HX90V. The BMS handshake completed on first install in both units. Charge acceptance, discharge curve, and battery-remaining display all behaved normally through full cycles.
- First-cycle calibration on Sony bodies: On first install, run one complete charge cycle through the camera body or OEM charger before heavy shooting. Sony's BMS maps the discharge curve to its indicator system during that first cycle — skipping it can cause the battery-remaining display to read inaccurately for several sessions.
Sony BMS rejecting a third-party NP-BX1 on first install
Some Sony bodies run an authentication check when a new cell is inserted. If the camera shows a battery error or refuses to power on with a fresh replacement, it does not always mean a faulty cell. The BMS needs one charge cycle initiated from within the camera body to register the new cell. Insert the battery, connect the camera to its USB charger or dock, and allow a full charge to complete before shooting. After that cycle, the error clears in most cases.
Battery percentage jumping or reading 0% on a charged cell
This happens when Sony's fuel gauge hasn't yet mapped the new cell's discharge curve to its voltage thresholds. The indicator system was calibrated against the original cell's degraded curve, so a fresh cell discharging at a different rate causes erratic percentage readings. Run two full charge-discharge cycles through the camera body. By the third cycle, the gauge recalibrates and percentage display stabilises.