Nightstick XPP-5570 Replacement Battery 3.7V 3400mAh

Nightstick XPP-5570 / XPR-5572 — 3.7V Li-ion Replacement Battery (5572-BATT)

This is a 3.7V, 3400mAh Li-ion replacement battery for the Nightstick XPP-5570 and XPR-5572 rechargeable flashlights. It uses OEM part number 5572-BATT and slots directly into the battery compartment on both models. Capacity is rated at 12.58Wh — matching the original cell specification.

• XPP-5570 and XPR-5572 compatibility: Both lights share the same battery format, voltage rail, and connector pinout. The XPR-5572 adds a charging contact plate on the tail, but the cell itself is identical — same 3.7V nominal, same physical dimensions at 116.00 x 47.65 x 26.20mm.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the XPP-5570 driver board. The BMS accepted charge from the OEM cradle without error flags, and the protection circuit tripped cleanly at the expected low-voltage cutoff threshold.
• Turbo mode draw management: The XPP-5570 driver pulls significantly higher current in turbo mode than in standard or low. Avoid leaving the light in turbo mode on a nearly discharged cell — the driver will step down output abruptly as the cell voltage sags under load, which some users mistake for a faulty battery.

Why the XPP-5570 dims suddenly before the indicator reads low

The XPP-5570 driver uses brownout protection that steps output down when cell voltage drops under load — not when the indicator crosses a threshold. In turbo mode, current draw is high enough that a partially discharged cell can sag below the driver's cutoff voltage mid-use, triggering a step-down even while the gauge still shows charge remaining. This is normal driver behaviour, not a cell failure. Switching to standard mode at that point lets the driver operate within the cell's deliverable current range.

Battery draining significantly faster than expected in turbo mode

Turbo mode on the XPP-5570 draws five to ten times more current than standard mode, so the cell depletes at a proportionally faster rate — this is not a defect. If the discharge rate seems excessive even in standard mode, check whether the cell has been repeatedly drained close to zero: Li-ion cells lose capacity when cycled to very low voltages. A healthy replacement cell should hold above 3.0V under standard-mode load; if it sags below that quickly, check the charger is delivering a full 4.2V termination voltage before use.