Use 12v fans for your ESC/motor...

[glassdoctor]

I didn't forget ;)

I was trying to give a basic example to answer the question about how much juice/runtime a fan uses. I wasn't even thinking of BG's converter... and I was thinking 4s too.

Assuming the fan pulls x current, without regard to the input voltage from the battery. Higher voltage would result in higher amp draw from the fan anyway, which changes the #'s.

So maybe we can go back and figure in the losses from the converter and the draw from a given fan @ 12volts... add them and see what the total effect is.

[BrianG]

Yeah, I forgot to figure in the effect in the runtime.

Using a fan off a 5 or 6v switching UBEC is actually more efficient that using a 12v regulator to power the 12v fan even thought the 5v one draws more current since the 12v regulator is linear.

Just for reference, most of the small, moderate airflow 12v fans draw between 0.05 and 0.08A each. As you get bigger and/or get ones with more airflow, current can get up to 0.75A for extreme cooling. But the smaller 40mm fans are fine... :)

At any rate, unless you're running lots of fans (3+), the effect on runtime is minimal and can be measured in seconds. This is just a cheap and dirty way to be able to use very commonplace 12v fans without overpowering them with full battery voltage.