DC buck converter ..20v 2amp.. with LCD display.. BOOST?

I use this device to limit voltage into a fan whose hub gets too hot at battery charging voltages. The output voltage stays the same no matter the input voltage.

http://www.amazon.com/DROK-Adjustable-Regulator-Experimental-Converter/dp/B00BYTEHQO/ref=sr_1_1?ie=UTF8&qid=1407222286&sr=8-1&keywords=DC-DC+Voltage+Regulator

I just found one of my T10 LED bulbs starts flickering at voltages under 11.5. I'm not taking my batteries that low, but this same distribution point feeds my laptop, which can take 90 watts and pulls down the voltage on the circuit, so it would be nice to have an adjustable boost converter too.

at this moment ... no intended use
i was perusing electronics on Amazon and this came up, in the "recommendations"
based on my previous history

my fridge is 120vac residential
i was thinking about some of the LED conversions.. needing stable voltages ..lower or higher than RV battery

Hi Mr Wizard,

Do you intend to use this to protect the computer boards in the Fridge etc? I see the output is limited to 2 amps. That way you could equalize without worries?

It looks nice.

I wonder if output voltage is a constant, or if it varies with the input voltage?