12v, 5v fan and 7.2V batteries?

[dugrant153]

I currently have a 12V fan drawing current from my 7.2V batteries in order to cool down my ESC and motor.

however, I was thinking of getting a 5V fan so that the fan is always running the fastest it can. However, will it blow up if I put it with a 7.2V battery?

(My Tamiya ESC uses the Battery slot in my receiver, so I can't just plug the fan into the receiver like most are built to do)

[rcguy2477]

While you do run the risk of ruining the fan, many people do use 5v fans. With the 12v fan, the fan is basically useless because its rpm is so low that there's barely any air being pushed across the motor.

[ikraj]

You can use the 5V fan with your pack...I doubt it will burn out because of the type of motor that is on the fan...it will run 50% faster...and you only run it for 5+ minutes at a time...that should not be a problem ... Anyway, being that these fans are so inexpensive the worst thing that could happen would be to replace it. If you want to avoid the posibility of a short you can use a mini 1A fuse in series with your fan just to protect your battery pack. This will not affect the pack performance at all.

[AudiTT-Quattro]

The 5volt fan running on 6 cells will be fine. I recommend using the Reedy type 25mm fans. They push a lot of air for such a small fan, more air than any 40mm fan I have seen.

[ikraj]

Do you know the CFM rating on the Reedy fan?
YOu can get a 25 mm fan from Sunin that has an airflow of 1.83CFM (cubic feet/minute) it only draws 60ma / 0.3W @5V. That is a decent ammount of air...and very little current drain. I have a 40mm that delivers 8.6CFM but the current drain is way too much for this application...700ma @5V I use them to cool batteries after they are used...DO NOT USE THEM TO COOL BATTERIES WHILE YOU CHARGE THEM.

[ikraj]

(My Tamiya ESC uses the Battery slot in my receiver, so I can't just plug the fan into the receiver like most are built to do)

Do you have an extra slot on your receiver for another channel. If you do you can plug your fan into the receiver, it does not matter on which channel or on the battery plug, as long as you have an open plug you can hook up the fan there. Just watch the polarity so the fan will flow in the right direction.

[AudiTT-Quattro]

Do you know the CFM rating on the Reedy fan?
YOu can get a 25 mm fan from Sunin that has an airflow of 1.83CFM (cubic feet/minute) it only draws 60ma / 0.3W @5V. That is a decent ammount of air...and very little current drain. I have a 40mm that delivers 8.6CFM but the current drain is way too much for this application...700ma @5V I use them to cool batteries after they are used...DO NOT USE THEM TO COOL BATTERIES WHILE YOU CHARGE THEM.
Unfortunately I don't know the CFM for the Reedy fan. I don't even know the company that manufactures the fan for Reedy (there is no label). However, I will check to see how much current the thing draws so we can at least get some side-by-side comparison with the Sunin fan.

[dugrant153]

Do you have an extra slot on your receiver for another channel. If you do you can plug your fan into the receiver, it does not matter on which channel or on the battery plug, as long as you have an open plug you can hook up the fan there. Just watch the polarity so the fan will flow in the right direction.

Unfortunately, I don't. All 3 slots on my receiver are used by the ESC and servo :(

[ikraj]

Unfortunately, I don't. All 3 slots on my receiver are used by the ESC and servo :(


Why don't you use a "Y" and then you can attach your fan to one of the slots. You can make one or just buy it. It's less than $2.50 for a "Y" adapter.

If you need one I can help you.

ikraj ;)

[dugrant153]

sure, I could use some help :)

Well, the thing is, my ESC has a red connector that goes into the BEC slot (the last slot) in my receiver. My option for the 5V fan is to solder it directly to the battery, or maybe "y-connect" (solder) it to that wire that's going into the BEC slot.

[ikraj]

sure, I could use some help :)

Well, the thing is, my ESC has a red connector that goes into the BEC slot (the last slot) in my receiver. My option for the 5V fan is to solder it directly to the battery, or maybe "y-connect" (solder) it to that wire that's going into the BEC slot.

dugrant153,

Why don't you give me your ESC manuf and model # so that I can give you a more educated answer. Now, if you connect your fan to the wires that are going into the receiver you will be getting around 5V regulated from the ESC. That will ensure that your fan will work just fine. I think this is the best solution. I don't like to attach anything else to the batteries. Additionaly, every time you solder your pack (unless you use connectors) you will have to solder the fan wires. They are very thin (20AWG) and the heat will get to them. (from soldering and the heat generated from your pack)

The reasonn I asked for the specs on your esc is to help you with the best solution instead of just guessing. I want to see the regulated output voltage and current rating. I do not forsee any problems as the fans draw very little current. Also, what car is it on and what servo are you using. I ask just to figure your amp load to ensure we do not overload the BEC.

Also, I may figure a better way to wire your ESC with just one connector instead of two. Tell me what receiver you are using, please.

With all that info we will figure the right way to get your fan working.

I hope this helps you.

ikraj
Axxis Racing (http://axxis-racing.com)

[dugrant153]

hey ikraj,
don't think I have the manual in PDF (I could mail it to ya... hah! but we'll see).

The ESC is a Tamiya TEU101-BK. http://www.tamiyausa.com/product/item.php?product-id=45029
My servo is a Futaba S3152 digital servo.

Right now, my 12V fan (which runs at 0.08A) is hooked up to the batteries wires from the ESC, so it starts up the moment I connect the battery.

[ikraj]

hey ikraj,
don't think I have the manual in PDF (I could mail it to ya... hah! but we'll see).

The ESC is a Tamiya TEU101-BK. http://www.tamiyausa.com/product/item.php?product-id=45029
My servo is a Futaba S3152 digital servo.

Right now, my 12V fan (which runs at 0.08A) is hooked up to the batteries wires from the ESC, so it starts up the moment I connect the battery.


Hi dugrant153,
I went to the link that you sent me to but there are no specs nor I could tell if there are two plugs that go to the receiver. Anyway, if you want to put a fan and you think that it will help you, I do not forsee any problems if you just make or buy a "Y" to hook up the fan. If you are doing this make sure youuse a 5V fan, not a 12V because it will be very inefficient and you will not beneffit from it.

GOOD LUCK

[dugrant153]

ah, here's a better link ;)
http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXGMR6&P=7

[AudiTT-Quattro]

In this case, I would be rather conservative on overloading the BEC since the BEC output on the ESC is only rated at 1amp. Running the digital servo and receiver alone would pretty much suck that up already.

ikraj, I've heard from a source that the 25mm Reedy fan pushes 2.2CFM which is incredible! I won't question the validity of that number until I see something better though.

[ikraj]

In this case, I would be rather conservative on overloading the BEC since the BEC output on the ESC is only rated at 1amp. Running the digital servo and receiver alone would pretty much suck that up already.

ikraj, I've heard from a source that the 25mm Reedy fan pushes 2.2CFM which is incredible! I won't question the validity of that number until I see something better though.

AudiTT-Quattro, that is achievable...and it sounds like a reliable number...The 1.8 CFM fans have been tested and at times I have measured up to 2.2CFMs out of them..hmmm...I wonder...that seems to be the high side for the ones I sell, but I use conservative numbers...if you run a 5v-1.8CFM fan at 7.2V you will get that rating or higher for sure.
The majority of the 5V- 25mm fans are rated under 1CFM. The rason is that they have such a low profile that you can only pitch the fan props so much...otherwise, higher CFM ratings could be achieved.

Thanks for the info. I appreciate that a lot, it helps to know more...

Stay in touch

[dugrant153]

hey ikraj, do you have a picture of a Y-connector? is it just one wire that splits into two?

I'm still concerned as to what the BEC (red plug) plug does from my ESC and how much voltage it puts out.

[ikraj]

hey ikraj, do you have a picture of a Y-connector? is it just one wire that splits into two?

I'm still concerned as to what the BEC (red plug) plug does from my ESC and how much voltage it puts out.

dugrant153, yes a "Y" is a wire that has two connectors on it. Just split your wires, solder another set of wires to the existing wire that you split, make sure you insulate your connections and you ar done. You can also buy a ready made one at any hobby shop.

The voltage is not the issue here, it is probably around 5V. The issue has to do with how much current your regulator (BEC) can supply. The Esc does not draw any current from the BEC, only your servo and fan will. If your fan drwas under 100ma I don't think yu will have any problems. I am going to take a look at your ESC spec sheet and give you a for SURE answer in a few hours. I am just very bussy at the moment. Just wanted to get back to you ASAP.

Let me know how it goes...

[dugrant153]

will do :) just have to get a 5V fan now :(

quick question. Does running a 12V fan bog down the power going to the car motor and steering servo? Or is that more based on amps?

cuz my fan is rated at 0.08A, 12V (it's a CPU fan that I'm using right now)

[ikraj]

will do :) just have to get a 5V fan now :(

quick question. Does running a 12V fan bog down the power going to the car motor and steering servo? Or is that more based on amps?

cuz my fan is rated at 0.08A, 12V (it's a CPU fan that I'm using right now)

Depends where you hook it up to. But since it only draws 80ma it should not affect your output as long as you have good batteries. Are you going to run the 12V fan from the 5v BEC? If you are using a 12V fan I think it will be much better to hook it up to your battery pack. 80ma is nothing compared to what your motor and servo draw, and getting the extra 2.2+Volts will make a huge differnce on the fan performance. I would not hook it up to the BEC. The voltage is way too low for your fan.

If you have a 25mm fan I believe it is rated at 2.4CFMs @ 12V. If you hook it up to your battery you dshoul be able to get around 1.3CFMs.

Is your fan a SUNON by any chance? the specs are just like it.

Hope that helps...

[ikraj]

will do :) just have to get a 5V fan now :(

quick question. Does running a 12V fan bog down the power going to the car motor and steering servo? Or is that more based on amps?

cuz my fan is rated at 0.08A, 12V (it's a CPU fan that I'm using right now)

Since it only draws 80ma it should not affect your output as long as you have good batteries.To figure out how much power it consumes we use WATTS, and you figure that by this formula...W=V x C ...As you can see it is a function of both, A (amps) and C (current in amps)
Are you going to run the 12V fan from the 5v BEC? If you are using a 12V fan I think it will be much better to hook it up to your battery pack. 80ma is nothing compared to what your motor and servo draw, and getting the extra 2.2+Volts will make a huge differnce on the fan performance. I would not hook it up to the BEC. The voltage is way too low for your fan.

If you have a 25mm fan I believe it is rated at 2.4CFMs @ 12V. If you hook it up to your battery you shoul be able to get around 1.3CFMs.

Hope that helps...

[ikraj]

dugrant153, I just looked at your ESC specs and the output voltage from the BEC is 7.2V. Voltage wise it will be the same wherever you decide to hook it up to, the question is now the current. This depends on your servo, but I still think that you have enough with 1A to power both. I doubt your servo will pull 800+ma

Sorry for that, I should haver checked the SPECs before I gave you an answer.

ikraj

[dugrant153]

haha... that's fine.
yeah I figured it'd be 7.2V anywhere with this ESC, strangely enough.

Which means that if I run a 5V fan, I might blow it?

Is there a way to increase the voltage to the fan (so I can just keep the 12V fan?)

thanks!

[gizmoguy303]

I don't believe you will ruin your 5.0v fan if you run it on 7.2v.

The time it would take to construct a simple DC-DC converter to boost 7.2v to 12v and then position the circuit in your car would probably outweigh the effort of just buying a new 5.0v fan. I would try using a 5.0v fan, and if for some odd reason it fails, switch to a 12v fan. :)

Or you may be able to wire in two diodes in series to bring the 7.2v down to a milder 6v for the fan. I am sure ikraj can elaborate more on this.

[dugrant153]

hmm... a diode, eh?
yeah that would probably work well. My 12V fan seems to do the job okay, but I notice that when I press the throttle, the 12V fan slows down O_O... aiyah!

So thinking 5V fan would be able to get the most power out of it. hmm... are you sure a 7.2V wouldn't fry the 5V fan? too much voltage = heat up fan?

[ikraj]

hmm... a diode, eh?
yeah that would probably work well. My 12V fan seems to do the job okay, but I notice that when I press the throttle, the 12V fan slows down O_O... aiyah!

So thinking 5V fan would be able to get the most power out of it. hmm... are you sure a 7.2V wouldn't fry the 5V fan? too much voltage = heat up fan?

It makes sense that your 12V fan slows down when you accelerate. The reason is that your batteries cannot handle the high current demand from the motor and the voltage drops for a few ms. that is normal. Now, that can be fixed to a point with a capacitor in parallel with your batteries. What you need to do is to put a 4700 or 6800 uf 15V electrolytic capacitor in parallel with your ESC/batteries.

Regarding the fan and voltage, your best solution is just to get a 5V fan. That is the most logical and inexpensive solution. I would still recommend to add the capacitor to your ESC. Now, about dropping the voltage from 7v to 6 or to 5, yes you can do that with silicone diodes like an IN914 or any one of the IN4XXX family, every diode drops 0.7v, if you want to go to 5v, you need to add 3 diodes in series. They cost around 6 cents each, but in reality you do not need them. Nothing will happen to a 5V fan running at 7.2V for a few minutes.

My recomendation to you is to get a 5V fan and just get it over with. That way you know you will get enough airflow to cool whatever your intentions are. Also, I do recommed you to install the capacitor to prevent that instantaneous loss of voltage.

If you need any more help and/or explanations feel free to ask. Good luck

ikraj :)

[dugrant153]

hey, I was talking to my friend and he's running a 470uF 10V cap with his ESC.
He mentioned that the largest he has is 1000uF 10V.... soo... hmm... is there a discrepancy here?

As soon as I can find a good deal, I'll probably get a 5V fan. A cooler motor is a faster motor, and a more efficient motor that lasts longer.

[thewarrenator]

can someone give a diagram showing how to assemble the diodes with the 5vfan? i bought one and have diodes so i need to know how to assemble them, i have a ai pro reverse 10t limit esc.

[thewarrenator]

are these the right diodes?...in4148

http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&product%5Fid=276-1122

[dugrant153]

ikraj said to put them in series. I guess you put them in series along one side of the 5V fan? Not sure. :P
Wish I could draw a diagram for you, but I'm not entirely sure how it works either. But yeah... I think they go in a series right next to the fan
(not on both sides, if I got it right?)

Well, a friend of mine gave me a 4700 uf 35V capacitor AND a 1000 uf 10V capacitor.
I just bought a 5V fan, so I'm wondering if I raelly need the 4700uf 35V capacitor or whether the smaller one will do?
thanks!

[thewarrenator]

im thinkin it should be like one of these, which one?...

http://i16.photobucket.com/albums/b3/teamlosikiksae/diode.bmp

or

http://i16.photobucket.com/albums/b3/teamlosikiksae/diode2.bmp

or

http://i16.photobucket.com/albums/b3/teamlosikiksae/diode3.bmp

notice the polarity

[ikraj]

The way you want to hook up your diode is as follows:
The diode has a band on it, pay close attention as polarity is very important. The band is the CATHODE or the - side of the diode, the + side is known as the ANODE

Hi guys, I hope this will help you.

Wire in series this way... Battery pack + , then diode (end that does not have a band, then the + end of your fan to the diode (to the end with the band), then the - side of your fan to the - terminal on your battery.

......no band----band side
battery (+)---Diode---fan(+)---FAN---fan(-)---battery(-)

I hope this will help you. You can add multiple diodes in series, each diode will drop 0.7v, just keep the polarity straight. non band to band to non band to band, etc. The band end of the diode should be pointing towards the (-) end of your battery.

I hope you understand the little script diagram I made for you.
If you need more help let me know.

The diode you bought should be OK since it can handle up to 400ma (i think...my memry is starting to fade at times :rolleyes: )

ikraj
Axxis Racing (http://axxis-racing.com)

[ikraj]

ikraj said to put them in series. I guess you put them in series along one side of the 5V fan? Not sure. :P
Wish I could draw a diagram for you, but I'm not entirely sure how it works either. But yeah... I think they go in a series right next to the fan
(not on both sides, if I got it right?)

Well, a friend of mine gave me a 4700 uf 35V capacitor AND a 1000 uf 10V capacitor.
I just bought a 5V fan, so I'm wondering if I raelly need the 4700uf 35V capacitor or whether the smaller one will do?
thanks!

dugrant153, the problem with a 470uf or 1000uf capacitor is that they will not hold the voltage for more than a few tenths of a milisecond. You need atleast a 4700uf capacitor to hold the voltage long enough to make a difference. The 470uf caps were used many years ago when the motors did not pull as much current as the newer ones do. The capacitor was used mainly as a noise filter to avoid glitches, a 470uf cap cannot hold much voltage for any decent time...In simple words, such a small cap will not help at all. If you want to stabilize the voltage I would use the highest rated cap possible without sacrificing weight or space, an 8200uf will be even better since you are getting such a noticeble voltage drop...higher rated caps are just too big...in size I mean!

If you need help getting the caps let me know, I have all of them.

ikraj
Axxis Racing (http://axxis-racing.com)

[thewarrenator]

so like this...

http://i16.photobucket.com/albums/b3/teamlosikiksae/diode4.bmp

[thewarrenator]

right?

[ikraj]

right?

You got it!!!
Thats the way...

Remember that each diode will drop 0.7 Volts.
Make sure you keep your diode leads as short as possible and insulate them. You do not want to leave anything exposed as you could short your battery pack.

Good luck to:thewarrenator

[thewarrenator]

thank you much ikraj

[thewarrenator]

what about putting a piece of tubing over the whole configuration and zip-tieing each end, i dont think these things get that hot, do they?

[ikraj]

what about putting a piece of tubing over the whole configuration and zip-tieing each end, i dont think these things get that hot, do they?


Use heat shrink, zip ties are way too big for such a small diode/wires. Get shrink wrap at RS if you need it. That is much better than a tube and ties.

Keep it simple!

[dugrant153]

dugrant153, the problem with a 470uf or 1000uf capacitor is that they will not hold the voltage for more than a few tenths of a milisecond. You need atleast a 4700uf capacitor to hold the voltage long enough to make a difference. The 470uf caps were used many years ago when the motors did not pull as much current as the newer ones do. The capacitor was used mainly as a noise filter to avoid glitches, a 470uf cap cannot hold much voltage for any decent time...In simple words, such a small cap will not help at all. If you want to stabilize the voltage I would use the highest rated cap possible without sacrificing weight or space, an 8200uf will be even better since you are getting such a noticeble voltage drop...higher rated caps are just too big...in size I mean!


I guess I'll stick on the 4700uf 35v capacitor then :) Although, it is quite huge. Hard to find a place to put it cuz it's so huge.

[thewarrenator]

fan works great...

http://i16.photobucket.com/albums/b3/teamlosikiksae/fan004.jpg

http://i16.photobucket.com/albums/b3/teamlosikiksae/fan003.jpg

[ikraj]

I'm glad to see that you wired your fan. Is it working the way you expected it?

It's nice to see people like you that ask a question and then go ahead and proceed with their project. It looks nice!!!

Do you see a diference in performance with the fan? Does your ESC run cooler? Let me know. :)

[thewarrenator]

i dont know what it ran like with 7.2 so i wasnt sure what to expect. the esc does runs cooler, i can touch it without being burned...haha

[thewarrenator]

im gonna go run it now,