NP-900 Maginon Slimline X50 Replacement Battery 3.7V 600mAh

Maginon Slimline X50 Series — 3.7V Li-ion Replacement Battery (NP-900)

This is a 3.7V, 600mAh Li-ion cell built to the NP-900 form factor. It fits the Maginon Slimline X50, Slimline X4, Slimline X60, and DC-6600, among others. Dimensions are 43.70 × 31.30 × 7.00mm — same physical footprint as the original cell.

• Slimline and DC-6600 compatibility: These models share the NP-900 voltage rail and connector pinout. The BMS in each body reads cell voltage the same way, so one battery type covers the full lineup without adapter or modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the bench. The BMS accepted the cell without error flags, and voltage held steady across the discharge curve with no mid-cycle cutoff events.
• First-use charge cycle in the camera body: Insert this battery and charge it once through the camera body before shooting. Some Maginon BMS firmware maps the battery-remaining display against the first charge cycle it records — skipping this step can cause the indicator to read inaccurately from the start.

Why the Slimline X50 shows a dead battery indicator on a partially charged replacement cell

The Slimline X50 battery indicator maps display segments to voltage thresholds calibrated against the original cell's discharge curve. A new third-party cell can have a slightly different curve shape — the camera reads voltage correctly but assigns it to the wrong display segment. This is not a fault with the cell. One full charge-discharge cycle inside the camera body lets the BMS re-anchor its threshold mapping to the new cell.

Battery percentage jumping erratically on the Slimline display mid-shoot

Erratic percentage jumps happen when the camera's voltage-to-percentage lookup table doesn't align with the replacement cell's discharge profile. Under load — autofocus, flash recharge, image write — voltage briefly dips, and the camera interprets that dip as a lower state of charge than it actually is. The reading then recovers when draw drops. Complete one full discharge to below 3.4V, then charge to 4.2V in the camera body to recalibrate the indicator.