Vivitar ViviCam 3945S Replacement Battery NP-900 3.7V 600mAh

Vivitar ViviCam 3945S — 3.7V Li-ion Replacement Battery (NP-900)

This is a 3.7V, 600mAh lithium-ion replacement for the OEM NP-900 battery cell. It fits the Vivitar ViviCam 3945S and several other ViviCam compact digital cameras including the 3830, 5340s, and V45. Dimensions are 43.70 × 31.30 × 7.00mm — verify against your original cell before ordering.

• ViviCam compact platform fit: The ViviCam 3945S, 3830, 5340s, and V45 share the same battery bay geometry and voltage rail. All run the NP-900 footprint, so one cell covers the group without modification.
• Bench tested on actual hardware: We cycled this cell through the ViviCam body and monitored BMS handshake on first charge. The protection circuit triggered correctly at cutoff voltage and the camera body accepted the cell without error flags on subsequent power-on.
• First-use charge protocol for ViviCam BMS: Run the first full charge cycle inside the camera body using the original charger cable, not a third-party USB adapter. The ViviCam BMS calibrates its fuel gauge against the charge curve during this first cycle — skipping it causes the battery indicator to read inaccurately throughout the cell's life.

Why the ViviCam 3945S battery indicator jumps erratically after replacement

The ViviCam's battery display maps percentage to voltage thresholds calibrated against the discharge curve of the original cell. A new replacement cell — even at the same rated capacity — discharges along a slightly different voltage slope until it is broken in. This mismatch makes the indicator skip from 80% to 20% without warning, or hold at full then drop suddenly. Run two full charge-discharge cycles through the camera body and the gauge mapping stabilises against the actual cell curve.

ViviCam showing "no battery" with a freshly inserted replacement cell

This happens when the cell arrives at or near the BMS low-voltage lockout threshold — typically below 3.0V — after sitting in storage. The camera cannot draw enough current to boot and flags the bay as empty rather than reporting a low charge state. Do not assume the cell is faulty. Place it in the camera, connect the OEM charger, and allow a minimum 15-minute charge before powering on. If the camera accepts charge and the LED activates, the cell is functional.