Black Diamond ReVolt 350 Replacement Battery BD1800 3.7V 1100mAh

Black Diamond ReVolt 350 / Sprinter Series — 3.7V Li-ion Replacement Battery (BD1800)

This is a 3.7V, 1100mAh Li-ion cell replacing OEM part BD1800 in Black Diamond headlamps. It fits the ReVolt 350, Sprinter 275, and Sprinter 500. When the original cell degrades and your headlamp stops holding a charge through a full outing, this cell restores full output without replacing the headlamp body.

• ReVolt 350, Sprinter 275, and Sprinter 500 compatibility: These three headlamps share the same battery bay dimensions, connector orientation, and 3.7V nominal voltage rail. The driver circuit in each model communicates with the cell through the same contact points, so one BD1800-spec cell covers all three without modification.
• Bench tested on actual hardware: We ran this cell in a ReVolt 350 through full charge and discharge cycles. The BMS accepted charge without fault flags, stepped down output correctly as voltage dropped, and cut off cleanly at low-voltage threshold without driver stutter.
• Single-cell headlamp storage: If you're storing this headlamp between seasons, discharge to roughly 50% before packing it away. Storing a Li-ion cell fully charged or fully flat accelerates capacity loss — 50% keeps the cell chemistry stable during long idle periods.

Why the ReVolt 350 steps down brightness before the battery indicator triggers

The ReVolt 350 driver uses brownout protection — it monitors cell voltage in real time and steps output down when voltage sags below a threshold, even if the battery indicator hasn't flagged low yet. This is intentional. A high-drain burst on a partially depleted cell can cause a sudden voltage dip that the driver reads as a brownout risk. The result is a visible dimming before any low-battery warning appears. Switching to a lower output mode at that point stops the stepdown and stabilises output until the cell reaches its actual cutoff voltage.

Headlamp powers on but drops to minimum output immediately

This usually means the cell voltage has dropped below the driver's operating floor — typically around 3.0V on this platform. The driver defaults to its lowest output mode rather than shutting off, preserving some usable light. A cell in this state may not recover to full capacity with a standard charge cycle if it has been sitting deeply discharged for weeks. Put the cell on a USB charger and check the voltage after 30 minutes — if it hasn't climbed above 3.2V, the cell has degraded past recovery and needs replacement.