Window 12v vent fan - removable

hulagun

Haulin' A** since 1974
I want to assemble a rigid insert for one of my cab windows that incorporates bug mesh and a 12v silent fan (approximately 5" fan size, one or maybe two smaller ones). It would only be used occasionally, when camping or sleeping in the van. The other window would get a matching insert with no fan. My idea is to get some cross ventilation, even just a little.

There's a lot of inexpensive 12v fan options on the internet, mainly offered for computers. Can I get some advice here on which fan to use? Ideally something easily wired by me to have an on-off switch and a couple of speeds. No fancy LED lighting. I'd be OK with only one speed if it was quiet. It will be powered by a cord and 12v plug on the dash or added to the door pillar trim.

I'll post photos of this little project soon as I can.

Thanks in advance!
 

GaryJ

Here since 2006
O2 Cool makes a very quiet 10" fan that runs on 8 D size batteries or 110V AC with an adaptor to 12V. Since 8 x 1.5V just happens to equal 12V an easy cig lighter adaptor can be made. On low the fan draws 0.7A and high, 1.0A and even has a jack on the side for the 12V input. Picked mine up a couple of years ago at Walmart in the camping/outdoor section. I've learned that anything that runs on disposable batteries has to be rather efficient not to kill the batteries too quickly. And the larger diameter the fan given equal amounts of air flow, the quieter it will be. Its those really high speed small fans that make the most noise for the air they move.

Leaving the passenger side rear door ajar but locked and wedged out against the lock will provide front to rear airflow with the fan running. I've also seen where someone created a way to have the door locked but open a couple of inches.

Gary
 

d_bertko

Active member
If you are going to build a window insert anyway then you might build it match an airdock template. That would give you hvac and cable tv at truck plazas across the country.

Not something you'd use much of the time but maybe a useful summer or winter travel feature.

Dan
 

autostaretx

Erratic Member
I want to assemble a rigid insert for one of my cab windows that incorporates bug mesh and a 12v silent fan (approximately 5" fan size, one or maybe two smaller ones).
A typical "computer 5 inch" fan moves about 225 cubic feet of air per minute.
The one i've linked to up there draws 3.6 amps when running.

Your Sprinter probably has 500 to 600 cubic feet inside, so (if it was 100% per cent efficient in terms of air exchange) a 225 CFM fan would give you a total air exchange every 3 minutes or so.
They're not exactly quiet when moving that much air. (65 dB for that one)

You can find specifically "quiet" fans, but they move less air.
Example ... but it only moves 46 CFM (at only 20 dB)

Note that the Maxxfan (etc) use 10 to 12 inch fans. (allowing slower, thus quieter, speeds to achieve the CFM airflow)

--dick (looking at the same thing...)
 
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Stone Lake

New member
Hey Hulagun
I have a great quiet fan for you. I have used these things on my boat for cross ventilation and they work like a charm. Use it all summer and the batteries never gave out. "D" size. Virtually silent. Really moves a lot of air on all speeds. Just bought a couple more for our RV. These things are so cheap that originally I expected them to fail miserably. But to my surprise, they worked much better than expected. You can move them around, adjust air speed ,flow angle and they have a nice heavy base that does not move around. Very small and easy to store.

Good Luck

Maxam Battery Powered Portable Fan

Just go to Amazon and buy a couple of them. Keep it simple
 

hulagun

Haulin' A** since 1974
Hey guys thanks for the replies. I have some specific reasons for my "design", so I want to stick to my plan. My needs and reasoning are as follows:

- for stealth: should not be too obvious or too loud
- for security: not easily removed when door is locked
- capacity: cycle the entire van (450-500 cf) about every 15 minutes
- for sleeping: low hum OK
- size: must fit in front side window
- bugs can't come in whether running or not
- rain can't come in (luckily my van already has Lexan air deflectors on front windows)
- NO cutting of sheet metal, van roof (and floor) stays unmolested
- 12v power
- not intended to create a breeze (I'll use other 12v fans or battery powered fans for that)

Based on this I want this thing to fit into the upper 5" of one front window, and simply exhaust some warm, moist, or stale air, very quietly. Cross ventilation should be achieved by opening the opposite window (fitting a bug screen or other insert, if needed). Eventually I'll be installing CR Laurence windows in both sides of the van, and those can be opened to allow fresh air in.

Dick, I could use TWO 4 or 5 inch fans side by side, vs one 10" super obvious fan. To be run singly or paired as needed. I realize noise might double with both running. But at 46 cfm, one 5" fan such as the one you referenced would do the job, I suspect.

Can anyone advise how to wire a 12v fan and a switch to get some form of speed control?
 

NBB

Well-known member
I think building something into the window to mount a computer fan would look a little ghetto.

I run an "Endless Breeze" fan by Fantastic. I really like it and run it pretty much 100% of the time I'm parked and sitting in the van. I also have a roof vent fan. The combo works well. Otherwise, I think the van is a stale sardine can, can't stand being in it.

The Endless Breeze will circulate enough air to exchange it through any nearby window, doesn't need to be mounted in it.
 

autostaretx

Erratic Member
I could use TWO 4 or 5 inch fans side by side, vs one 10" super obvious fan. To be run singly or paired as needed. I realize noise might double with both running. But at 46 cfm, one 5" fan such as the one you referenced would do the job, I suspect.

Can anyone advise how to wire a 12v fan and a switch to get some form of speed control?
Quick and very dirty: run the two fans in series for "slow", and parallel for "fast".

You can achieve that with a double-pole, double-throw, center-off switch, thusly:

fans.jpg

I'm not at all sure how well a PWM (pulse width modulated) speed controller will work with a brushless DC motor... the motor has internal controlling circuitry which "steps" the current around to the three coil sets pulling on the permanent magnet rotor.
But the PWM may well work, i simply don't know (and am cautious). (and it's a very cute controller)
Check with the brushless manufacturer's spec sheets.
Some PCs certainly adjust their fan speeds depending upon cooling needs, but it's usually been more of a "two level" control than continuous (which a PWM would provide). They could just be putting a resistor in series with the fan (or switching to a 5v source in the PC).

--dick
p.s. by the same cautious token, the switching of each motor's coils will make the "series" connection see really choppy waveforms... the PWM would probably be better.

How brushless motors work: http://youtu.be/bCEiOnuODac and http://youtu.be/oFI7VW6WGR4
 
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hulagun

Haulin' A** since 1974
I think building something into the window to mount a computer fan would look a little ghetto. .
Point taken, but you apparently haven't seen stuff I've designed and built, or where I live.... LOL
 

hulagun

Haulin' A** since 1974
I run an "Endless Breeze" fan by Fantastic. I really like it and run it pretty much 100% of the time I'm parked and sitting in the van. I also have a roof vent fan. The combo works well. Otherwise, I think the van is a stale sardine can, can't stand being in it. The Endless Breeze will circulate enough air to exchange it through any nearby window, doesn't need to be mounted in it.
How do you keep the mosquitos out? Unless you have side windows with screened openings then it's mosquito mesh pan held on by velcro or magnets - which IMHO also "looks a little ghetto".... LOL

I'm not camping for weeks in my little (118" wb) sardine can, just sleeping in it for a night occasionally. So my ventilation needs are modest compared to some others, I think.

And I have already researched roof vent fans... I like the idea. But after reading posts about potential roof vent fans issues (cracking, leaking, rust, reduced clearance) I'm going to hold off for awhile. If my ghetto window fan idea is inadequate, I can always install a roof vent fan later.
 

Graphite Dave

Dave Orton
Mother nature decided to make hot air rise. If you want good air circulation use her gift. An opening down low and another up high creates air flow without any noise when van interior temperature is higher than the exterior temperature.

Worthless without the temperature differential. Roof opening does not need to be powered fan. A small flat openable skylight would work.
 

hulagun

Haulin' A** since 1974
Here's what I came up with. A pair of daisy chained 80mm 5 volt USB powered fans from ebay. A pair of 3" screened floor vents (see photo). I'll post fan photos later...
 

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Kevin.Hutch

2011 Mercedes 313 906
Here's what I came up with. A pair of daisy chained 80mm 5 volt USB powered fans from ebay. A pair of 3" screened floor vents (see photo). I'll post fan photos later...
My van came with a long horizontal vent in the step area to meet Aus requirements for ventilation when a gas stove is installed.
I found two problems with it;
1. The road noise makes it sound like the sliding door is not shut properly.
2. Open a front window on a dirt road dust comes in through it.

Solution a piece of rectangular PVC duct with foam filters in both ends mounted in the long void behind the step.
Fans could be mounted in the duct.
1599341508912.png
 
Thanks for the info! Did you build a frame for the two fans and were you able to accomplish your goals of:
- for stealth: should not be too obvious or too loud
- for security: not easily removed when door is locked
- capacity: cycle the entire van (450-500 cf) about every 15 minutes
- for sleeping: low hum OK
- size: must fit in front side window
- bugs can't come in whether running or not
- rain can't come in (luckily my van already has Lexan air deflectors on front windows)
 

hulagun

Haulin' A** since 1974
Thanks for the info! Did you build a frame for the two fans and were you able to accomplish your goals of:
- for stealth: should not be too obvious or too loud
- for security: not easily removed when door is locked
- capacity: cycle the entire van (450-500 cf) about every 15 minutes
- for sleeping: low hum OK
- size: must fit in front side window
- bugs can't come in whether running or not
- rain can't come in (luckily my van already has Lexan air deflectors on front windows)
See photos. I hacked together a prototype using 3/16" PVC sheet (edited) from TAP Plastics. Cut the holes with a hole saw. My prototype achieved 90% of the above. I can't measure the air exchange speed but the two little 80mm fans create noticeable movement of air inward at the floor vents, which are the same diameter. Screens are available but since I was using such small fans I decided against fitting them on the fans for now, as they block a lot of flow. The fans draw less than 0.3A total I believe are 5 volt and plug into a USB adapter. I ran them all night on medium speed and the van barely noticed. Slept like a baby. One thing I will do differently on the next version is create a better fit where it hugs the glass. The current design leaves small open gaps that a mosquito might find.
 

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I like that design. It looks like you have two sheets of the ABS that you sandwiched together so that the window would slide between the two sheets to lock it into place. when the window is rolled up against it. Would that be correct?
Thanks again
 

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