Maximum CFM/ Amperage (12v fan application)

[Euclid]

I'm looking for a 12v fan (I suppose it could be 5v or 24v instead).
I'd like to keep it under a couple watts if possible.

My optimum size would be ~80mm.

I have a relatively sealed enclosure (~36"x6"x6") with quite a bit of resistance that I'm trying to keep cool.


What kind of fan/setup would you guys suggest? Case fan? Squirrel cage type? Push/Pull, one on each end?

I figure this subforum is about as knowledgeable as it gets while talking about 12v cooling applications.

Thanks!

 

[silent-circuit]

80mm, 106CFM, 61dB, under 2 amps draw startup and sustained. Hope you don't like your ears.

Delta Part # PFB0812UHE
CFM	106.26
Noise dB(A) 61.0
RPM	7500
Weight (grams)	205g
# of Directional Blades 7
# of Fan Blades	9
Rated Current - Amps (startup) 1.86a
Rated Current - Amps (sustained) 1.55a
Rated Input Power - Watts 18.60w
VDC Range 7.0 to 13.2w
Maximum Air Pressure - mm H²0 34.75

I'd personally step it up to 120mms if you can. The bigger Deltas can push a lot more air, and if you could fit a pair of 120mms you could do it with Panaflos or Scythe Ultra Kazes and keep your hearing.

Some of the 120mm Deltas push over 250CFM. Granted, they will deafen you and startup is around 5A but once they get going it's under 2.

 

[Euclid]

Going back over my available power, looks like I'm not going to be able to just brute-force this cooling issue like I would have liked to.

I need to keep it down to as little total power as possible.

 

[Euclid]

So far the best I've found is the SAF-B82 with 34.23CFM and 1.2w. Only $4.95, too.

 

[silent-circuit]

Find more power somewhere. 34CFM (and thusly almost certain to be shit for static pressure) isn't likely to do a damn thing in a restrictive situation.

 

[Deleted member 184142]

1. Can you fit a 120mm?

2. Why the power usage?

3. If its for lack of supply why not pick up a cheap a molex connector PSU?

4. Whats this going in?

 

[Euclid]

Right now I'm running a single fan at the end of each box @ 34.4CFM and 1.92W

It works, but not good enough.

First order is to add a second fan to the other side of the box. Push/Pull setup. Do you agree?

Here is my research thus far (since making this post)

Fan (80mm)	                Airflow (CFM)	  Power (W)	 Price ($) 
KDE1208PTV3     	    	31                	0.84		7.00
GELID Silent 8      	 	20.72             	0.96		4.99
NFB0812M                   	32.28	                1.2	 	6.00
Blacknoise M8-S2	  	26.4	                1.2	       	17.95
Blacknoise M8-S1		17.6	                1.2	       	17.95
KDE1208PTV2	              	36.5	                1.2	        6.00
SAF-B82	                	34.23	                1.2	        4.95
Arctic Fan 3	                 28	                1.44	        7.95
KDE1208PTV1	                 40	                1.56	   	6.00
5912-3412M	                 42	                1.8	      	25.88
CURRENT SETUP	 		34.4	                1.92	     	0
Blacknoise M8-S3	 	34.73	                2.04		17.95

Which case fan manufacturers are on top of their game? I've checked out Sunon and Delta.
Sorting through hundreds of datasheets more-or-less blindly isn't much fun

 

[silent-circuit]

If you're not concerned about noise, Delta wins. Then Sunon and Panaflo.

If you are concerned about noise the situation becomes far more complex.

Where are these boxes?

 

[Euclid]

If you're not concerned about noise, Delta wins. Then Sunon and Panaflo.

If you are concerned about noise the situation becomes far more complex.

Where are these boxes?

They're full of batteries... it's for an off-grid solar application.
Delta doesn't seem to have very good efficiency as far as CFM/Power, unless I'm missing one of their model lines.
Sunon MagLev is the best so far (see table above).

 

[Deleted member 184142]

They're full of batteries... it's for an off-grid solar application.
Delta doesn't seem to have very good efficiency as far as CFM/Power, unless I'm missing one of their model lines.
Sunon MagLev is the best so far (see table above).

Delta, Sunon, Panaflo are OEM fan manufactures, don't believe the other fan ratings for CFM, they all fudge their numbers. With this being solar, I am seeing that efficiency will be top dog, so if I were you I would find a way to get a 120mm fan in there, an 80mm is just not going to cut it, the higher into the RPM rage you go the more its going to drop off for power to CFM.

 

[Euclid]

Delta, Sunon, Panaflo are OEM fan manufactures, don't believe the other fan ratings for CFM, they all fudge their numbers. With this being solar, I am seeing that efficiency will be top dog, so if I were you I would find a way to get a 120mm fan in there, an 80mm is just not going to cut it, the higher into the RPM rage you go the more its going to drop off for power to CFM.

Some modification will allow 120mm fans to be used.
I actually just remembered those 120mm->80mm adapters as well, maximizing velocity will help to push air through these puppies a bit better as well, eh?

I'll pull down some 120mm data.

 

[Deleted member 184142]

These are not cheap at 17 bucks a pop, but these Deltas move a good amount of air, and being 38mm have much better pressure for pushing through restrictive spaces.

120x120x38mm
75.93 CFM @ 2000 RPM
34.0 dBA
1.92 watts, .16 amps
Maximum Air Pressure 4.00 mm H²O

 

[Euclid]

Thanks for that link.

Am I correct in my assumption that two fans would be much more efficient at cooling?
you think i'd be better off with a single fan with twice as much power or two separate fans (one on each end, blowing in/out).

Fluid dynamics really isn't my forte'

 

[Deleted member 184142]

Thanks for that link.

Am I correct in my assumption that two fans would be much more efficient at cooling?
you think i'd be better off with a single fan with twice as much power or two separate fans (one on each end, blowing in/out).

Fluid dynamics really isn't my forte'

For this application I would have to say yes, because you would start seeing a reduction in efficiency of CFM to watts, as you would really start to climb in the RPM range, as you will see with fans in the 3000+ RPM range and 100+CFM range, their power consumption really goes up, 10watts+. And would give less restriction to a single 80mm inlet/outlet, I also highly suggest you open up the holes to the full 120mm size and redrill the mounts for the fans, as with the adapter you will only be adding more restriction to an already restrictive environment.

 

[Zero82z]

Thanks for that link.

Am I correct in my assumption that two fans would be much more efficient at cooling?
you think i'd be better off with a single fan with twice as much power or two separate fans (one on each end, blowing in/out).

Fluid dynamics really isn't my forte'

Using two fans with the same CFM rating will not increase your volume of airflow. However, it will increase your static pressure, and help ensure that the air passes through a restrictive area more effectively. If the box you are trying to cool is indeed very restrictive, having a second fan on the other end could be quite helpful.

 

[BillParrish]

I do not understand the restriction issue, if these are vent fans for a battery box there should be little or no restriction at all and they really should not be needed for cooling as your charge controller should have a thermocouple that montiors battery temp and limits the charge to prevent battery overheating or at least limits the bulk charging based on battery voltage. Warm batteries are not a huge issue as they store more energy when warm and are constructed to handle it.

Your hydrometer should have the thermometer built in so that you can adjust the specific gravity readings for temp. Under a heavy bulk charge what is the temp of the battery water ?

Standard design is to have an intake fan down low to pull in cool ambient and a vent pipe of PVC with a fan either blowing up the vent pipe at the box or mounted at the top of the pipe pulling the hydrogen gas out. Even if there is only a 3/8 inch between the fan and the battery the resistance would be medium at worst.

(Take the over all dimensions LxWxH to get the box volume (~36"x6"x6" = .75 cubic feet ) and then take the LxWxH of a battery to get its volume, x the number of batteries and subtract the two to find out what is the "free air" volume of the box. That will help you determine what CFM you need to change the air in the box over some unit of time and size the fans.

My concern is that the fans typically are not considered as cooling devices for the batteries but mainly to vent the hydrogen gas. Due to the construction of the batteries (thick plastic case, close spacing, etc. ) the fans will prevent heat buildup in the enclosure but do little to reduce the internal temp of the batteries when under bulk charging. If you are aware of this there is no concern otherwise I am concerned you are going to use a significant amount of power running high rpm fans that will not end up doing what you want. ( hmm I see you have seen that - nm)

All that said, that is a very small battery box and from the size it seems you are not using standard size batteries or the larger solar/off-grid typical batteries. So all that above would seem to not apply, So perhaps you are indeed trying to cool the batteries. I envision a box 36 inches long, 6 inches high, six inches deep stuffed with batteries laying flat on the bottom of the box in a single row with little or no clearance to the side of the box, minimal or no spacing between each battery and maybe an inch of space at the top ???

If so, frankly my advice would be to rebuild the battery box making it just a bit wider, and longer, put two strips of wood (plastic would be better) in the bottom to raise the batteries off the "floor" 3/8 inch or so. and allow some room between the side of the box and the battery (3/8 inch would do) and spacing between the batteries in the string.

My new point being is that the "free air volume" of the box is very small and if your fan is doing even 10CFM you are changing the air in the box over 10 times a minute when empty. The trouble is the battery spacing does not allow any airflow around the batteries themselves because they are packed in so tight, and all the airlfow in the world over the tops of the batteries will do little to cool them. Of course if the batteries do have spacing I am completely wrong in my assumption.

What is the box constructed of ?

Are these lead/acid batteries ?

just some ramdom thoughts in an attempt to help. More specific information on your battery box/batteries would be of interest.

 

[Euclid]

Your hydrometer should have the thermometer built in so that you can adjust the specific gravity readings for temp. Under a heavy bulk charge what is the temp of the battery water ?

There are a few (~600) Lithium-Ion batteries, so water temp doesn't really apply.


Minimum airflow requirements showing to be ~280litres/minute according to this analysis:
That converts to only about 10 CFM so I've shifted my focus from CFM/watt to pressure/watt (to compensate for the restrictive environment)

Also, the 120mm Delta fans only put out about .008inH20 more than my lowest power 80mm fan.

 

[Euclid]

I've also been reading up on the differences between axial (case fan) and centrifugal (blower) fans in "ducted" environments.
Looks like blowers have a much better airflow in high-pressure (restrictive) environments, although I'm not sure if my case is extreme enough to warrant it.

There's so much theory here!

 

[BillParrish]

here is a resource
http://rexususa.com/fan-main.html

You want to click the manuf links where provided and look at the pressure vs cfm curve and current/wattage draw although as you will notice the power usage of the fans are only given in free air. How the power draw goes up with increased back pressure is seldom if ever shown.



I realized something special was going on.

Very nice. Very high end.

A "quickie" off of the cuff, yes the second fan will help a lot, something I think you have already arrived at. And if you can go up to 120mm better yet. Even 90mm fans would help. Going to study your layout and think a bit.

A blower would be the way to go to overcome static back pressure but the noise and mounting concerns might be an issue. Not to mention the expense but you must have a decent budget as that is way over the top for a normal battery bank. Very [H]ard.

One way to cut the static pressure each fan would see in half would be to have a fan on each end blowing in and an exhaust fan in the middle.

So we are looking for (if we stick to fans for the moment) - What fan delivers at least 10CFM at some arbitrary high static back pressure the most efficiently (lowest wattage).

The other concern I have is that I would not care about price with that investment in batteries, Panasonic (panaflow/NMB) Delta, Roton, Sunon. etc. I would only buy a brand that is an actual manufactures brand and someone that provides commercial fans.



Other random thoughts , since this is not my Dads battery bank, a small temp reading pwm fan controller would be the cats meow to reduce fan wattage when not needed. Its current draw would/should be less than the saving in power to the fans I would think or perhaps a solar cell to cut the power to the fans as you are not going to need them running when you are not charging and you will only be charging when the sun is out. You may want to consider some kind of fan fail or over temp alarm. This could be as simple as a microswiitch with a vane attached so (for example) when the sun is out and you are charging, the solar cell allows current to feed the fans and in parallel a microswitch with a vane attached so that the air stream will push the vane keeping the microswitch open and not sending current to a buzzer or indicator lamp or some sort. Fan fails, airstream goes away vane Goes to rest position closing microswitch and sends current to buzzer or indicator. It could be done with rpm monitoring etc but KISS is always best.


I am agreeing with the posters above, switch out to a 38mm thick 120mm fan and the low speed panaflow would be my move or a 2nd 80mm intake at the other end and if possbile a 120x38 mm low or medium speed exhaust in the middle

hmm what if the ends where open/perforated, the fans there done away with and a single (or heck 2 if you want) middle 120mm x 38 as exhaust pulling air in from each end. would the static pressure the fan "sees" then also be halved ? I think so.

Mounting/space concerns may eliminate the possibilty of a middle mounted fan but I think I would explore that if at all possible. It cuts the problem in half.

 

[Euclid]

Another thing that I should add is that I have ~4' of (horizontally laid) aluminum dryer hose ventilating the airflow in/out of a confined space. Noise is not a concern and budget is relatively flexible.

I've already got a few temp/fan management circuits in place (batteries have different temp limits for charging/depleting). I've also got fan fail/temp alarms in place (auto shut-off).

Space concerns are very important here. I've got very very little additional room to work with.

Thanks again for your input, I'll check out the links that you've provided.

These puppies are being ridden hard and put up wet.