SeaLife NP-900 Reefmaster DC 500 Compatible Battery 3.7V 600mAh

SeaLife Reefmaster DC 500 — 3.7V Li-ion Replacement Battery (NP-900)

This is a 3.7V, 600mAh Li-ion cell built to fit the SeaLife Reefmaster DC 500 underwater camera and the S5 variant. It replaces OEM part numbers NP-900, 02491-0015-00, BATS4, and 02491-0037-00. If your original cell no longer holds charge through a dive session, this is the direct swap.

• Reefmaster DC 500 / S5 compatibility: These models share the same battery bay dimensions and 3.7V single-cell architecture. The connector orientation and cell footprint — 43.70 x 31.30 x 7.00mm — are identical across the DC500 and S5 variants, so one SKU covers both without adapter modification.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on DC 500 hardware. The BMS accepted the cell on initial insertion, reported charge state correctly, and held voltage through sustained shooting without triggering an early cutoff.
• First-use charge cycle on the Reefmaster DC 500: Charge the new cell inside the camera body using the OEM cable before your first dive. The DC 500's battery indicator calibrates to the cell's discharge curve during that first in-body charge cycle — skipping it can cause the remaining-charge display to read inaccurately underwater.

Battery percentage jumping erratically on the DC 500 display

The Reefmaster DC 500 maps its battery indicator to fixed voltage thresholds tuned to the original cell's discharge curve. A new replacement cell discharges at a slightly different rate, especially in the mid-range, which causes the indicator to skip levels or drop suddenly. This is a calibration issue, not a cell fault. Run one full charge-to-empty cycle in the camera body and the indicator will track more accurately on subsequent charges.

DC 500 showing dead battery indicator on a freshly charged replacement cell

A replacement cell that has self-discharged during storage can drop below the DC 500's minimum recognition voltage — typically around 3.0V for single Li-ion cells. The camera's BMS sees the low resting voltage and flags it as a dead or incompatible battery rather than attempting to charge it. Place the cell in an external Li-ion charger first and bring it above 3.2V, then insert it into the camera. The body will then recognise the cell and complete the charge normally.