Nightstick XPP-5570 Replacement Battery 3.7V 2600mAh

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

This is a 3.7V, 2600mAh (9.62Wh) lithium-ion battery for the Nightstick XPP-5570 and XPR-5572 tactical flashlights. It replaces OEM part 5572-BATT directly. These lights are used by law enforcement and emergency personnel, so a dead battery at the wrong moment is a real operational problem.

• XPP-5570 and XPR-5572 compatibility: Both models share the same battery bay dimensions, cell voltage, and connector pinout. The XPP-5570 is the intrinsically safe variant; the XPR-5572 is the rechargeable version. One battery format serves both because the driver circuit voltage requirements are identical across the pair.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the XPR-5572. The BMS held cutoff at 3.0V under load and accepted a full charge without thermal flag. Output stayed stable across all driver modes until the protection circuit engaged near depletion.
• Turbo mode draw management: The XPP-5570 turbo mode pulls significantly higher current than standard or strobe modes. Running turbo continuously stresses the cell and trips the BMS sooner than the mode indicator suggests. Use turbo in short bursts and step down to high or medium for sustained operation.

Why the XPP-5570 dims before the low-battery indicator fires

The LED driver in the XPP-5570 uses brownout protection that steps output down when cell voltage drops below its threshold — typically around 3.2V under load. This happens before the indicator circuit reads the voltage as critically low, because the indicator samples at rest voltage, not loaded voltage. The gap between the two readings widens as the cell ages. If you see the beam dim but the indicator hasn't flagged low battery, the cell voltage is sagging under draw. Switch to a lower mode immediately or swap the battery.

Driver mode-cycling or flickering when the battery is nearly flat

When the cell drops close to the BMS cutoff threshold, the driver repeatedly tries to pull current, trips the protection circuit, then resets — causing the light to cycle through modes or flicker. This is not a faulty driver; it is the BMS preventing over-discharge. It will not resolve by toggling the switch. Remove the battery immediately, check resting voltage — it should read above 3.0V for a healthy cell — and charge before reinstalling.