Fey Elektronik PA-UL-LNB19 Compatible Battery 3.7V 3350mAh

Fey Elektronik PA-UL-LNB19 — 3.7V Li-ion Replacement Battery

This is a 3.7V 3350mAh (12.4Wh) Li-ion battery pack built to the Fey Elektronik PA-UL-LNB19 specification. It replaces the original pack in devices that call for this OEM part number. Dimensions are 66.50 × 21.65 × 18.60mm — confirm these against your existing pack before ordering.

• PA-UL-LNB19 compatibility: Devices spec'd to this part number operate on a 3.7V nominal rail with a charge ceiling of 4.2V. The replacement pack matches that voltage window and connector footprint, so the host device charge circuit sees no deviation from the original.
• Bench tested on actual hardware: We ran this pack through charge and discharge cycles on the bench. The integrated BMS held cutoff at the correct low-voltage threshold and did not trip under normal load profiles. Charge acceptance was consistent across the test units we pulled.
• First-cycle calibration: Battery packs with an integrated fuel gauge need one full charge-to-discharge cycle after a swap to recalibrate the state-of-charge counter against the new cells. Until that cycle completes, the capacity indicator may read low or erratically — this is expected behaviour, not a fault.

Pack not accepted by device after swap

Some devices that use OEM battery packs run a voltage range check or BMS handshake before allowing operation. A freshly shipped pack sits at storage voltage — typically 3.6V or below — and may fall outside the window the device expects on first insertion. The fix is straightforward: connect the pack to a compatible charger before inserting it into the device. Once the pack reaches full charge at 4.2V, the host device's acceptance check passes cleanly.

Pack not reaching full charge on the first cycle

On new Li-ion cells, some charge ICs apply a reduced current during the first charge cycle as a conditioning step. This can make the pack appear to stop charging early or show a lower than expected state of charge. It is not a fault with the pack or charger. Run one complete charge cycle through to termination and the charge IC will apply full current on subsequent cycles.