Nightstick 9500 Replacement Battery 3.7V 6800mAh

Nightstick NSR-9500 Series — 3.7V Li-ion Replacement Battery (9600-BATT)

This is a 3.7V, 6800mAh Li-ion cell built to replace the OEM 9600-BATT in Nightstick's 9500, 9600, and 9900 series tactical flashlights. These lights are used in law enforcement and search-and-rescue, where a degraded cell means a light that steps down at the worst moment. Capacity figure is sourced from product data, not estimated.

• 9500 / 9600 / 9900 platform fit: These models share the same tube diameter, cell format (139.40 × 24.00 × 24.00mm), and driver voltage rail. The BMS handshake and charge termination logic are matched to this cell spec across all three variants.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a 9500-series host. The BMS stepped down output correctly at low-voltage threshold and accepted a full charge cycle without fault flags or thermal cutoff events.
• Single-cell replacement protocol: The 9500 series runs one cell. If you're replacing it because runtime dropped sharply, check the charge contacts in the tube for corrosion before fitting the new cell — a resistive contact forces higher current draw at the cell level and accelerates the next cell's wear.

Why the Nightstick 9500 steps down output before the indicator shows low

The 9500's driver uses brownout protection to step down output when cell voltage drops under sustained high-current draw — typically in turbo or high mode. This can happen well before the charge indicator triggers, because the indicator reads resting voltage, not loaded voltage. Under a heavy draw, the cell's internal resistance causes a larger voltage sag than the indicator accounts for. If you see the light step down unexpectedly, switching to a lower output mode lets the cell voltage recover and extends usable output.

Turbo mode cutting out far sooner than standard mode

Turbo mode on the 9500 series pulls significantly more current than standard or medium modes — often five to ten times the draw. A 6800mAh cell has fixed energy capacity; higher current draw depletes it faster and also increases voltage sag under load. When the sag crosses the driver's cutoff threshold, the light steps down or shuts off even though the cell still holds charge at rest. To reset the driver after a turbo cutoff, switch the light off, wait 10–15 seconds for cell voltage to recover, then restart on a lower mode.