Fey Elektronik PA-UL-LNB46 Compatible Battery 3.7V 5200mAh

Fey Elektronik PA-UL-LNB46 — 3.7V Li-ion Replacement Battery

This is a 3.7V Li-ion battery pack rated at 5200mAh (19.24Wh), built to replace the original unit in the Fey Elektronik PA-UL-LNB46. It matches the OEM voltage and form factor. If your original pack has stopped holding charge or the device no longer powers on, this is the direct replacement.

• PA-UL-LNB46 fit: This pack matches the voltage rail and physical dimensions of the PA-UL-LNB46 battery bay. The 65.90 × 39.80 × 18.80mm footprint seats without modification, and the 3.7V nominal output stays within the device's accepted input range.
• Bench tested on actual hardware: We cycled this pack through charge and discharge on a matched load. The integrated BMS held voltage above cutoff throughout the draw cycle and triggered protection correctly at the low-voltage threshold — no passive drop-off.
• First-cycle calibration: If your device uses a fuel gauge or capacity indicator, run one full charge-discharge cycle immediately after install. New cells ship at storage voltage — the gauge reads inaccurately until it calibrates against a full cycle on fresh cells.

Pack running at lower voltage than rated on first install

Li-ion packs ship at storage voltage — typically 3.6V to 3.85V — not at full charge. On first insert, the device may display low battery or behave sluggishly because the resting voltage reads below the operating threshold. This is not a fault with the pack. Charge it fully before drawing any load, and the voltage will rise to the 3.7V nominal operating point.

Pack not reaching full charge on the first cycle

Some charge controllers limit current when they detect new or cold cells — the charge cycle appears to terminate early. The pack is not defective. The charge IC steps down input current on the first pass as a conditioning measure. By the second full cycle, the controller recognises the cell capacity correctly and charges to the full 5200mAh ceiling.