Running an 80mm fan off a battery

[pudds]

Is this possible? and if so how many hours would i get out of it?
I work at a school and for a project id like to use a fan , it would need to be on about 8 hours a day 5 days a week. Can anyone think of a way of powering it?
Mains power isn't really an option and the device to power it needs to be quite small, hence i was thinking batteries. The fan i have lying around draws 0.14A.

[Tyrou]

what kind of battery do you plan to use ?

it's possible :)

[matt9669]

I once ran a 120mm fan off a 9V when the power was out during the summer :lol: Alas, I only got ~4hrs out of it . . .

40hr/wk is not going to be possible with your average alkalines, at least not reasonably - you might be able to get away with 6 D cells in series but even then I'm not sure it would last the week . . .

I'd look for a larger 12V alkaline cell, I've seen these at Fry's - they would probably do the trick - but I don't have pics or a link or anything . . .

Of course, you're guaranteed this will work off a car battery . . . but, who wants to lug around a damn car battery . . . ;)

EDIT: sorry, that's 8 1.5V's in series, I was thinking 9V application :rolleyes:

[Butcher_]

Depends on your battery size, using commonly available 1.5V cells, you'll need 8 cells, and at 0.14A current you'll get up to about 50-60 hours depending on the actual batteries used (60 hours is with duracell ultra 'D' cells).

[Aphex_Tom_9]

I once ran a 120mm fan off a 9V when the power was out during the summer :lol: Alas, I only got ~4hrs out of it . . .

same here! haha

[pudds]

Just tried it with 8 1.5v aa batteries and it does work. Problem is i don't think the fan will be powerfull enough.
The thing im considering making consists of fan mounted below a tube which blows polystrene balls out of the tube. I won't go into any more details as i don't even know if that bit would work. I know my 120mm delta would do it :) but at 2A i don't know how much battery time id get out of it.

[smokey]

The only battery I know of that would give you that kind of time would be a lead-acid/gel-cell battery. They are used for high-availability applications requiring 36+ Ah discharge rates. Check out Power-sonic for some ideas of what I'm talking about. Avoid NiMH and NiCad batteries, they won't hold the kind of charge you need.

[Butcher_]

1.5V alkaline batteries won't deal well with such a high power drain - at drains over about 500mA their capacity drops significantly (think factor of 50 and you're not far wrong). At 2A you'll get about 15 minutes off 8 AAs. :p

[pudds]

Ive looked at gell cell and they look good but expensive, doubt the school will autorise it. Im considering mains powr now although i don't know how i would hook that up. Reason i didn't want to go with mains was the kids are likely to fiddle with the wires, suppose i could route it to the wall socket and box it in.
What im thinking of building is a large picture in a glass frame. The fans blows the polystrene balls up the tube, it hits a piece of wood at a 45 degree angle and rolls down a slope which is at the top of the pic. The slope has holes in it and the balls fall down to the bottom of the pic. Second slope at the bottom goes the opposite direction and the balls roll down back onto the fan.
Would look great with a winter scene, use petals for spring with different pic etc.
I think the biggest problem now is the power of the fan, id like something very large at least 1m high. Don't know what kind of fan i would need to blow the balls that high and with enough force.
Sorry if this post is a bit off topic. :)

[smokey]

What you need to look for is an old Lotto machine.

[VetteTheHeretic]

get one of those half size car batteries they use in small 4 wheelers and dirt bikes.

either that or get a hampster with a raging speed addiction on a wheel generator

[matt9669]

either that or get a hampster with a raging speed addiction
:ROTF: :bounces: :rotf: :hehe: :lol:

LOL Aphex - good to know I'm not the only nut around here with wire cutters and 9V batteries to spare! :D

[MaxxxRacer]

use a motorcycle car batery.. they work great for this kind of stuff. When i was into RC cars i used one to power my starter motor for the engines and the glow plug ignighter power.