high voltage cooling fan ?!

[oded mazor]

apply a higher voltage to the cooling fans

Hello,

need some help with the following,

I own a large electric RC helicopter. the motor is getting very hot after few minutes of flying. I would like to add a fan to cool it down a bit (not uncommon in RC helis).

the voltage of the Lithium Polymer battery I am using is around 32V (8 cells in series). I'll be using small computer type fans which are available at 5V and 12V.

can I connect two 12V fans in series (24V) with the higher voltage of the battery pack (over 30 volts) ? or is it going to toast the fans ? the fans will be operated for flights of 10 minutes max.

I would to keep it as simple as possible without adding resistors and such...

thanks.

 

[VVV]

Personally, I would build a step-down regulator, to power the fans at the correct voltage. As I recall the maximum voltage for the fans is about 13V, so you would be overdriving them. I am not saying that they would necessarily fail, but...

 

[lambtron]

I would build a step-down regulator ...

That's good advice, VVV. The fan voltage will be too high on both fans in the best-case scenario. It's also possible that the fan impedances will not be equal, leading to even greater stress on and likely failure of the fan that has the higher impedance.

You can get a switchmode regulator from National Semiconductor and other companies, all nicely pre-built on an eval board. Look for a lightweight unit that will tolerate 32V input and output regulated 5V or 12V at the current required by your chosen fans.

 

[vortechs2k]

Another solution could be to use something along the lines of what are used in aircraft computer cabinets. Try a search for Aerospace Blowers. They should operate at 30V or so and they will likely be lightweight.

 

[oded mazor]

thanks guys,

seems like a switching regulator to lower the voltage into the 12V neighborhood is a very good idea.

there is this very nice online electronic manufacturer that sells this kind of item (and many other for RC use) - https://www.dimensionengineering.com/DE-SWADJ.htm

I'll look into that.