[Nougatti]

Our "Voltswagen" has this red "trafo-charger" meant for charging forklifts etc.:

The picture is from before the car was completed.
During charging it gets rather hot, so we've installed a 12V computer-fan on the top of it (not in the picture. the fan was added later) which spins rather fast.
However, me and my friend are having quite a heated argument (no pun intended). He insists that I've installed the fan the wrong way. I've installed it so that it sucks air from outside and pushes it into the box. The charger has air-vents on both sides, about 3/4 of the way up, so in the current configuration, this is where the air comes out.
However, my friend insists that the cooling-effect would be much better if the fan sucked the air out, drawing in air from the side vents. Basically reversing the air-circulation.

So, who's right? I believe that either way works just as good, while my friend insists that the current way traps hot air inside the charger, since the vents aren't at the very bottom.

-Daniel

ps. Here's a vid of the build of the car and the car in action
We're using 48V from 8 12V gel-batteries connected in series-parallell with a total of 220Ah. We're using a Clark forklift-motor at 5.2 kW

http://www.youtube.com/watch?v=QDnR_if1Rao

 

[rabbithazen]

seeing as the fan is on the top of the charger. and heat naturally goes up. i think it would be better if the fan was blowing air out of the charger rather than into it. i have to take your buddys side. i may be new to this site but im not new to electronics.

 

[F16bmathis]

Most cooling fan installations I've seen suck/push air out.

 

[dtbaker]

heat naturally rises, so you would get better convection... only downside might be pulling hot air over the fan motor if it is not rated for hot air.

 

[Guest]

Have the fan mounted outside the box but pushing air into the box then vent out the sides. You want the fan to push in cool air and have no hot air going over the fan to heat the fan too. So push, don't pull. Shroud up the system so you get all the cooling air you can over your transformer in the charger.

Pete

 

[Nougatti]

Have the fan mounted outside the box but pushing air into the box then vent out the sides. You want the fan to push in cool air and have no hot air going over the fan to heat the fan too. So push, don't pull. Shroud up the system so you get all the cooling air you can over your transformer in the charger.

Pete

Yes, it's mounted on the outside of the box (no room for it on the inside).
What do you mean by shrouding the system?

Also, to all you others; Are there no other advantages for pulling over pushing apart from heat rising and therefore having the fan help out an already existing airflow? My friend was adamant that pulling would be better than pushing, regardless.

-Daniel

 

[Guest]

I just mean not air gaps between the fan and opening into the charger. That way all the cooling air is pushed inside. If your concerned about dust and dirt then you will need to build an air cleaner between the fan and box or before the fan which would keep the fan clean too. Otherwise just push that air in and keep your charger cool. Be sure there is plenty of space for that hot air move out of the way of he charger and so the fan won't pick up that hot air and push it back through.

Venting is just as important as getting cooling air in. No venting or not enough room to allow proper dissipation of the heat and it just gets sucked back through the system negating the purpose.

Pete

 

[icec0o1]

Yes, it's mounted on the outside of the box (no room for it on the inside).
What do you mean by shrouding the system?

Also, to all you others; Are there no other advantages for pulling over pushing apart from heat rising and therefore having the fan help out an already existing airflow? My friend was adamant that pulling would be better than pushing, regardless.

-Daniel

No, there aren't any other advantages. But computer fans aren't very powerful and the natural convection of a really hot charger might make up a large percent of the airflow. If it's something like 10-20%, you would either be cooling at 80% (pushing cold air in) or 120% by pulling the air out.

 

[Guest]

I'd use a big 6" fan rather than those tiny little 1 or 2" fans. Get a fan that can push some air. Your not cooling a computer, your cooling a high output charger. Get some air to that charger and let it stay cool. Push, pull what ever. I said the way I said because I thought of keeping the fan out of the stream. Push is my choice. If you have large enough vents then pushing is just fine. But get air. A computer fan is fine for computers.

Pete

 

[Nougatti]

I'd use a big 6" fan rather than those tiny little 1 or 2" fans. Get a fan that can push some air. Your not cooling a computer, your cooling a high output charger. Get some air to that charger and let it stay cool. Push, pull what ever. I said the way I said because I thought of keeping the fan out of the stream. Push is my choice. If you have large enough vents then pushing is just fine. But get air. A computer fan is fine for computers.

Pete

It's at around 10 cm in diameter. I don't know if it is meant for a computer, but it has a third wire which is probably used to "dim" the speed of the thing. We're not using that one so it's blowing at full steam. Computers seldom run them at full capacity due to the noise, I'd imagine.
I think we might add some ventilation-holes at the very bottom, or perhaps mount a small extraction-fan or two down at the sides, and lead the hot air through piping, into the cabin. Dual-purpose b!tches!

On second thought, the charger probably won't get hot enough to actually produce HOT air for the cabin with that fan running continuously, but hey, the idea was good

 

[F16bmathis]

My charger is mounted inside the cab. It keeps the cab warm in winter, and I crack a window in summer to let it cool off. I was thinking of venting the exhaust to outside during summer...