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

[BrianG]

Actually, if I really wanted to get anal about it, I would have written this:

In a linear regulator, no matter what the output voltage is, the current required by the load will be the same as the current from the battery. So, 1A at 12v will be 1A from the battery whether it's 15v or 200v. This is why they are so inefficient.

In a switching regulator, it's a power transfer. 1A at 5v UBEC output would be only 0.29A at 20v (assuming switching efficiency of ~85%).

:)

This is a great write up, but I have a question. I was putting one of these together and was applying the thermal compound and then I wondered what good it was doing. The electrical isolator is not a good heat conductor.

What were you using as an electrical isolator? Does it also conduct heat? I have a few heatsinks that I ordered from ebay for use on video chipsets. I think I'll just use some arctic alumina and glue one of those to the regulator. Will that suffice?

[Dafni]

Most fans I use are 5V, running them off the UBEC's 6V.
Sometimes I use 12V directly on the main batts. They seem to survive even on 5S setups :026: No doubt they are suffering, but if one goes, it just get's replaced. Usually they last pretty long, though. Can't remember when I killed my last fan.

[BrianG]

@AAngel: The insulator is used because the metal tab on many regulators is electrically the same point as the output of the IC. So, if you don't use it, the heatsink (and the shole chassis if you use the chassis as a heatsink) will be floating at 12v.

The pad I used is some kind of mica part that is electrically insulative, but thermally conductive. It's not really an ideal thermal conductor, but given the heat levels for this "circuit", it is more than adequate. I'd rather trade off a tad bit of thermal performance for the electrical insulative properties, especially since we dealing with power losses on the order of less than 1w.

@Dafni: I'm sure most fans have a working range. I just get real anal about running them (and anything really) higher than rated.

I try to avoid linear regulators these days. Check out www.dimensionengineering.com for a couple of choices for good quality switching regulators.

One could use a DE-SWADJ to regulate down to 12V from your main pack. Or you could use an AnyVolt Mini to step up from the receiver's 5V/6V to 12V.

Light weight and easy!

[BrianG]

True, the use of a switching regulator is definitely desirable in most cases, but the linear versions work fine for small loads below 100mA, especially for the price.

EDIT Oh, and I would never step up from a BEC's 6v to 12v. The BEC current would be twice that of the output current, not counting the efficiency factor. If your fan required 12v @ 0.2A, the BEC would be supplying a little over 0.4A @ 6v, which would take away from what the servo(s) might need. Always better to step down.