Need advice, adding FAN to ESC or E-bike controller

[spinningmagnets]

I noticed a while back that ESCs for RC cars usually already have a fan mounted over the heat-sink fins. Also, recently some questions were asked about cooling an E-bike controller that was partially hidden for stealth. Though the sizes between the two are different, the voltages and fan links are likely to be similar.

I have a couple ESCs that I want to add a fan to, and the computer CPU fans seem to be the right size, and the prices are very affordable. Here is a 2.8"/70mm fan with ball bearings for only $7
http://www.amazon.com/Masscool-70mm.../dp/B001BO6RWE?tag=viziom370nv37-inch1080p-20

Since these are a drop-in replacement for a burned fan, they just list which computer it goes to. They don't provide dimensions on the bolt-hole layout, or what RPM the fan spins at for the voltage supplied, or the various Cubic-Feet-[per]-Minute (CFM) of air that it moves at a given RPM, or even what voltage its designed to run at. (the label "looks like" it says DC 12V, can I run an inline resistor?)

The system I need it most on runs at 37V DC (10S-LiPo), but I also have a 24V ESC Id like to add a fan to, and I may eventually get a larger E-bike controller using 48V. Adapting a fan onto the fins is the easy part for me, I'm curious about the various electrical options and requirements. Thanks in advance...

 

[bobc]

Use a 5V fan & wire it to the BEC output?

 

[amberwolf]

The first thing I'd do is not use that kind of fan. I'd use a squirrel-cage type, to force much more air over things. If you have to mount it over the heatsink like that fan, then use the squirrel-cage open side down on the heatsink, and then aim the blower out whatever vent your stealthy setup has, or toward the rear of the bike if it's all open.

If you want to find fans that actually list specs for bearing type, RPM, CFM, power usage, voltage, dimensions, etc., Newegg.com is a good place to search. So is SilentCPU, and SilentPC (forums; not sure of URL ATM). Once you find the info you need, then maybe search for that fan's manufacturer & p/n on other sites if you don't like the prices at Newegg.

Keep in mind that noise ratings on various fans, and their CFM, are often not exactly accurate.


Regarding operating voltages vs pack voltages, you can do what he said above me as one option.

Another is to glue a small 7812 TO220 to the side of the fan, running the 7812 off your pack voltage and the fan off of it, if the pack isn't more than 24-32V. You might need a heatsink for the 7812, though. It's a power wasting linear regulator, but it will work ok with the small load you're dealing with and low pack voltages.

 

[aaronski]

damn, i just tossed 50 of those fans in the trash. actually the recycling.
a couple things: some of those fans are PWM fans, and won't work on 12v DC properly.
actually, what you might want is a server rack type 48v fan:
http://www.excesssolutions.com/cgi-bin/category/12700
4 bucks, and will run right off of pack voltage at 36 or 48v.

 

[AussieJester]

I run a pair of 60mm fans near identical to the ones you pictured, they were scavenged from old AMD cpu heatsinks...I have mounted them on my Lyen 12fet Infineon power is supplied to them via one of Mr Lyens dc-dc adapters.

I experimented a lil with venting holes two ( i had a couple of 12fet housings) went from 52 holes down to around half that, i have two rows of 6mm holes above the Fets, another single row of 6mm holes on the opposing side of the case. Running both fans to blow inward you get HUGE amounts of air passing out the venting holes (as the Infineon is pretty much sealed unit with its rubber ends and grommets) The holes above the FETs shoot out most of the air as it is the path of least resistance, which also means the cooling air passes directly over the 12 Fets The noise is negligible IMHO.

Best of luck...

KiM

 

[spinningmagnets]

Thanks everyone for replying, you've given me a good start on this...

For an E-bike controller, the 48V aaronski link above looks to be the hot ticket. AJ, great idea on the holes right next to the FETs!...

If my friction-drive didn't need to be small as a requirement, I might be tempted to use a liquid-cool boat-ESC, and adapt on on of these combo Liquid heat-exchanger/fan units for cooling CPUs

Newegg.com (Thanks, AW!) has a good search engine with search filters (if you go to the Digikey site and type in "capacitor" it starts with 50,000 choices). "Case fans" are larger, and "CPU fans" are a little more ESC-sized. I will also search the other two links you supplied...
http://www.newegg.com/Store/SubCategory.aspx?SubCategory=574&name=CPU-Fans-Heatsinks

I guess it's time to fire-up a pot of coffee, and start the digging for info! Keep the suggestions coming in, I am likely to buy a half-dozen fans before this is over.

Does anyone know the simplest and best surface-mount temp-probe that can turn on-and-off a low-amp 12V to 48V fan?

 

[amberwolf]

Why not just start with one that's already temp-controlled?

There are a number of case fans like that, including some small 40mm units I've run across now and then (but mostly 80mm and 120mm).

Short of that, Newegg should also have temperature controllers for PC fans, some of which are just little things you stick inline with the fan connector to the motherboard or power supply, and a temperature sensor you stick on whatever object you're cooling. They don't usually have any settings to change, but come on as soon as things start getting "warm" (significantly above room temperature, probably over 100F).

 

[texaspyro]

Actually, I just built a fan controller for my I3010B charger power supply. The power supply is a Kao 28V,10.8A (300W) open-frame power supply that a local surplus store sells for cheap. These supplies just ooze quality. They ain't your typical Chinese crap. They look more like something that the Germans would build.

I mounted the power supply, power switch, and line filter in a small box not much bigger than the supply. Sealed up, with no load the supply would heat to around 125F (a 50F rise over room temp). Would probably get rather toasty at full load so I added a rather small 50mm, 24V fan.

I modified the firmware in one of these LED dimmers http://www.dalewheat.com/tag/12v-dimmer-kit I replaced the control pot with an LM34 temperature sensor that is glued to the frame of the supply with homemade thermal epoxy (1500 grit silicon carbide mixed with epoxy). I replaced the mode button with a small blue LED that blinks out the temperature reading.

The firmware turns the fan on at 120F at around 25% speed and ramps up the fan speed as the temperature rises. At 160F the fan is on full. The fan turns off below 110F. When the fan first turns on, the firmware provides a 1/2 second burst of full power to make sure it starts spinning. The firmware was lifted from my high power LED controller.

I did the fan controller mainly for noise control. Even though the fan is not too noisy at full speed, it is almost totally silent at lower speeds. I have to put my hand over the vent to see if air is flowing. There is a small blue LED on the front of the box that blinks out the temperature reading. I may make it a red-green led that blinks red when the fan is on and green when it is off.

I am going to add the fan controller to a couple of my HP bench supplies (which I have already swapped out their louder-than-a-jet-engine 120V fans with 24VDC brushless fans).

 

[spinningmagnets]

The $15 dimmer with minor mods sounds interesting. I am not too concerned about fan noise with the RC-motor system, but a very quiet DD-hub with a 48V controller would probably really appreciate the automatic variable speed feature, which would make the fan as quiet as possible most of the time. It sounds like it powers a 12V fan, what are the power input voltages, and can they be changed fairly easy? (as long as it requires some mods anyways)

 

[texaspyro]

Dale ships his dimmer kit with a voltage regulator and FET that are good to 30V or so which is fine for my 28V fan. I usually replace the regulator with an ultra low power one rated at 40V (probably good to 60V) and the FET with a 60V one since that is what my LED driver uses. You could run the board off the controller's 5V line. It only draws a couple hundred microamps (without the blinkenlights).

You can get FETs that will switch voltages well past anything that you would find on an ebike. I have modded one of the boards that is driving a 120VDC 1/5 horsepower motor. I also have one driving a 2000W/48V composite curing oven.

I'm still playing with the temperature and fan speed thresholds to see what works best with my power supply. I'm a bit short on suitable loads to run it at the full 300W. I have the same power supply on my CNC mill stepper motor driver. That draws around 6A so I may try it there.

I also have some ultra-precision PID temperature controller code that I did for my GPS disciplined oscillator. It can control the device temperature to microdegree levels using just a cardboard box and a fan. Something like that could be ported to the board.

 

[spinningmagnets]

Should I look for 5 different FETs that will work for the five most popular input voltages? (18V, 24V, 36V, 48V, 72V) because bigger voltages mean a bigger FET?

Or could I find a single FET that would work well for the most popular voltage range (15V-55V), and another for the 60V-100V crowd?

Could you point me to a part number of a FET that you would recommend? I'm sure Digikey has about 10,000 choices and I don't know where to start.

Voltage regulator: Matt ships his Magura throttle with a tiny VR that takes all the popular E-bike pack voltages and drops it to a smooth 5V for a throttle power supply. Does anybody know if that VR can have its output adjusted to 12V / 24V to run these fans at their designed inputs?

edit: found a candidate for the list of possibles. $12, 24V, ball bearings, 60mm square (2.4")
http://www.buyextras.com/me60dc24vbab.html

And here's some tiny 5V fans, maybe an option for ESCs. Can be powered by the BEC (two of my ESCs have a BEC, the HV-one doesn't), just as bobc suggested.
http://www.buyextras.com/dc5vfaforlan.html

 

[spinningmagnets]

Been scanning a lot of computer fan sites. Common voltages are 5V, 12V, 24V, and 48V. Common diameters of the blades are 40mm (1.6"), 60mm (2.4"), 70mm (2.8"), 80mm (3.1"), 92mm (3.6"), and 120mm (4.7").

I went back to look more at the site aaronski listed. The smallest 48V fan they have is a 60mm, but interestingly, they have 3 different windings that they are calling medium, high, and Xtra-high speed. They might not have ball bearings, but as an experiment, they are only $4 each.

 

[John in CR]

Here's the little blower I use mounted to the controller end plate. It draws air in at the front of the controller and blows it out of the back. Intake, exhaust, and controller mounting angle are structured to make entry of water or debris very difficult. The solution is effective and quiet. I can just hear the fan when I turn the bike on before taking off, but never while In motion.

This little 2 watt fan does 4cfm, so the air inside my controller is being replaced a few times per second.

 

[AussieJester]

They might not have ball bearings, but as an experiment, they are only $4 each.

I had a box full of 60mm fans unfortunately not two the same (or so i thought) I bought 4 off ebay

http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item=270717638211&ssPageName=ADME:X:AAQ:AU:1123

Right after i hit the buy button and paid i of course found two matching fans amongst my stock LoL Anywayz have
4 of the above coming will add to the box of fans i have for future projects.

Took a HEAP of pics yesterday as it was the first outing for the new bike, controller never got even remotely
hot, i used the fans only on uphill sections of the ride (have bar mounted switch to control them) Will up
pics of the setup here soon as i get mates camera here to get images off.

KiM

 

[Hillhater]

You could always use the original ESC fans...they are available on Ebay for a few $'s
http://cgi.ebay.com.au/Hobbywing-Ezrun-5V-0-16A-max-7-2V-ESC-Cooling-Fan-auto-/180617884192?pt=RC_Modellbau&hash=item2a0daa3220

 

[texaspyro]

I bought some 20 ohm/50 watt resistors and built up a load bank that will pretty much fully load my 300W supply. Temperature in the box was pushing 140F at full load (actually that is quite acceptable), so I tweaked the fan parameters (on 50% at 120F, max speed at 136F, off at 110F). Under full load it now hits around 130F.

Under no load the temp cycles between 110F and 120F over a period of about 30 minutes (pretty fast cool down by the fan followed by a slow warm up to 120F where the fan comes on again).

I may implement the color coded led that flashes the temperature value in red when the fan is on and green when it is off. It would take an extra pin on the processor and I can just hook the LED to the two holes where the external switch previously went.