The RC40 features two buttons for operation. The right button cycles through the power levels: Eco, Low, Medium, High, and Turbo. Eco is 45 lumens for up to 125 hours, low is 500 lumens for up to 18 hours, medium is 2,000 lumens for a little over 4 hours, high hits 4,000 lumens for just under 2 hours, and the turbo mode will hit 6,000 lumens for 1 hour— but don't expect to run the flashlight at 6,000 lumens continously.
To prevent the LEDs from overheating, the light output will drop when the temperature hits 149 degrees Fahrenheit. This is typical in high-performance LED lights, which throttle output to protect the LEDs from damage. For what it’s worth, I ran the light on turbo mode on a cool night and didn’t notice any reduction in output after five minutes. Your mileage will vary depending on the conditions, of course.
The left button lets you activate the strobe, or SOS mode. Pressing both buttons locks the flashlight. If you try to turn on the light while locked, it will blink three times to let you know it’s locked.
The RC40’s negatives are its price, weight, and bulk.
Flashlight aficionados will bounce beams on a ceiling to measure relative output, and the RC40 will totally illuminate a small room. Like I said, I took the RC40 to an abandoned military base to creep around and could easily light up whole buildings 1,000 feet away.
The RC40 is what flashlight fans call a “thrower,” meaning its beam profile is better for lighting up objects far away. It’s bright enough to be competitive with less-efficient HID (high-intensity-discharge) flashlights while giving you better battery life.
Walking between the decrepit airplane hangers, I felt like I had a vehicle-mounted searchlight rather than a flashlight. The RC40 was bright enough to attract the attention of the sprawling base's sole security guard and get me kicked out.
You can thank Moore’s Law for that, as the efficiency of LEDs has advanced as quickly as computer processors. Last year’s RC40 could only push its four Cree XM-L U2 LEDs to 3,500 lumens. Without changing the power source, Fenix is now able to push six Cree XM-L2 (note the 2) U2 LEDs to 6,000 lumens.
The RC40 next to a typical D-cell incandescent flashlight.
So what are the negatives? The most obvious one is the power source. I have a large collection of flashlights and most of the higher-performance ones run on lithium-ion, as well. But they use commodity 18650 cells. The large ARB-L3-15600 in the RC40 is far from common. Replacements are about $65 on the internet and unless other flashlight makers or device makers support the form factor, you better hope Fenix keeps sourcing them for you. Should Fenix stop selling them, that’ll be it for the flashlight once the battery wears out.
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