About this replacement
Fitel Ninja Fusion Splicers — 14.8V Li-ion Replacement Battery (S946)
This is a 14.8V, 2000mAh (29.6Wh) Li-ion replacement battery for Fitel Ninja fusion splicers, including the NJ001. It replaces OEM part number S946. The Ninja series is used in field fiber optic splicing work, where a dead battery mid-job means abandoned fiber joints and re-mobilisation costs.
- Ninja series compatibility: The NJ001 and wider Ninja platform share the S946 battery format — same 14.8V four-cell Li-ion configuration, same connector, same BMS handshake protocol. Swapping packs between Ninja units in the field is straightforward with this pack.
- Bench tested on actual hardware: We cycled this pack through arc calibration and full splice sequences on a Ninja splicer. The BMS held stable through the electrode discharge pulse without tripping, and voltage recovery between splices stayed within the splicer's operating window.
- First-use calibration on the Ninja: After installing this pack, run a full arc calibration cycle through the splicer's calibration menu before heading to site. The Ninja maps battery state during calibration — skipping it causes the low-battery indicator to fire early, interrupting splice sequences on the first deployment.
Why the Ninja splicer shuts down during the arc discharge pulse
The fusion arc draws a short, sharp current spike each time the splicer fires the electrodes. An aged or deeply discharged pack sags below the splicer's minimum operating voltage at that exact moment, triggering an immediate shutdown. This isn't a fault with the splicer — it's the BMS protecting the cells. A fresh pack at full charge handles the arc pulse without voltage sag. If shutdowns keep happening after fitting a new battery, check the electrode condition — fouled electrodes increase arc duration and draw harder on the pack.
Pack will not charge after sitting unused in a carry case
Li-ion cells enter a deep-discharge sleep state when voltage drops below roughly 2.5V per cell — around 10V total for this four-cell pack. The splicer's onboard charger won't initiate a charge cycle at that voltage. Connect the battery to a Li-ion charger with a recovery or trickle-charge mode, which feeds a low current until cell voltage climbs above the charge-initiation threshold. Once the pack reaches approximately 12V, the standard charge cycle will begin normally.