NiKon EN-EL20 Replacement Battery 7.4V 850mAh Li-ion

NiKon 1 J1 / 1 J2 / 1 J3 / Coolpix A — 7.4V Li-ion Replacement Battery (EN-EL20)

This is a 7.4V, 850mAh Li-ion cell built to the EN-EL20 / EN-EL20a specification. It fits the NiKon 1 J1, 1 J2, 1 J3, and Coolpix A mirrorless cameras, along with five additional compatible bodies. The battery powers the camera's sensor, autofocus motor, and image processing unit.

• 1-series and Coolpix A compatibility: These bodies share the same EN-EL20 form factor, contact pinout, and BMS handshake protocol. One cell covers the full list — no hardware differences between variants.
• Bench tested on actual hardware: We cycled this cell through the 1 J1 body and monitored BMS communication across charge and discharge. The protection circuit responded correctly to cutoff thresholds and the body accepted the cell without error flags on repeated insertion.
• First-cycle charge protocol: Run the first full charge from inside the camera body using the OEM MH-27 charger or USB body-charge if supported. Some NiKon BMS builds require one internal charge cycle before the battery-remaining indicator maps correctly to the new cell's discharge curve.

Why the 1 J1 battery indicator reads full then drops sharply mid-shoot

The 1 J1 maps remaining charge by reading cell voltage against a stored discharge curve from the original NiKon cell. A new third-party cell has a slightly different voltage-to-capacity curve, so the indicator can read optimistic at the top of the charge then fall steeply once voltage drops past the camera's first threshold point. This is a calibration lag in the BMS, not a cell fault. After one or two full charge-discharge cycles through the camera body, the indicator tracking stabilises and becomes consistent.

Camera displaying "no battery" on a charged replacement cell at first insert

The 1-series body runs an authentication check on every new cell at insertion. If the BMS has not yet completed a full charge handshake with the replacement cell, it can flag the cell as unrecognised even when the cell carries a charge. The fix is straightforward: insert the cell, place the camera on charge via the MH-27 charger, and allow a full charge cycle to complete. Once the handshake completes, the body accepts the cell and the error clears — typically resolved at 8.4V full-charge state.