Question, 12V electrics.

[A19quattro]

I am thinking about using a radiator fan as an extractor in my garage, running from a battery, charged by a solar panel, yeah look at me, Ecoman
I have done this before but without the panel and just charged the battery as required. If I switched it on one day it would turn full pelt and if left it on it would usually still be turning the next day but very slow, battery almost flat. Is there a way I can drop the voltage to the fan to keep it running longer but slower, maybe even vary the speed as required?
I have done some 12V wiring in the past but resistors, relays etc are a mystery to me, appreciate some advice and an idea where I could get things from, preferrably second hand, maybe scrapyard or similar. It is a bit "Ghetto" I know and it suits me for it not to cost too much although I am genuinely concerned about the amount of mains items I have running at times (lights, power tools, heaters, compressor) and so trying to not add anything else to that.

 

[KrisKrk]

Do you have a separate fuse box for the garage? If so, is it powered from your house or direct from street mains?
If street mains, you shouldn't blow any fuse (if all are separated for lights, sockets, ect). You could ad on the fan to it.
If you have power from your house, can you rewire to a bigger fuse? This should allow you adding on the fan from that, not battery/solar panel.

On the other hand, why is your solar panel not charging the battery?
How big is the fan?

Can you not think of the bathroom fan? They usually have relay installed to work few minutes (or longer) after power cut-off. Dont think they consume that much power so with your "appliances" on, it should be fine (depending on power).

 

[A19quattro]

Cheers for the reply, the Garage is wired from the house but it goes through a 13 amp spur in the Kitchen which blows and takes out half the Kitchen and utility sockets and lights every time I run my compressor, so I don't any more. I need an electrician to sort this, the guy that was going to do it has become strangely unavailable lately so I came up with the 12v idea as this is what I did years ago at my old house. I just used a couple of car radiator fans attached to grills at the sides of my wooden garage and it workd reasonably well but the batteries flattened too quickly as they were running full speed all the time. I thought if I could reduce the voltage and speed and with the solar panel helping I though it could be a good way of removing stale air and preventing the place from becoming damp, maybe later I could consider adding another and do a wee bit of spraying but I think I ne,ed a smaller compressor to replace my too big and too small ones I have at present.

 

[desertstorm]

Something like this would probably do if it's a smaller car fan
http://www.ebay.co.uk/itm/20A-DC12V...or-Controller-Switch-Good-35DI-/401081142291?

UK supplied

http://www.ebay.co.uk/itm/NEW-6V-90...-36V-1000W-RC-Controller-TE095-/272471556759?

If you have more than 1 fan you can wire them in series so each fan gets 6v and runs at half speed.
Resistors are not good for motor speed regulation as with the current a motor takes they just get very hot and it's all wasted energy. Much better to use a PWM speed controller. A solar panel will take a very long time to charge a decent size battery until it's a pretty big size. Better off with some kind of trickle charger.

 

[SootySport]

Not enough light and your fan won't be running with a solar panel. Overall much easier to upgrade your electric supply to the garage. I like to have lots of light, heat and power for the tools, especially in the winter. Nothing worse than tripping the supply when busy on a project, you know it makes sense.