Finished a New RORO Shed

[PRejto]

My new MEII + dual TEC scopes required a new RORO shed for my deck. 10 days later I'm close to finished and only need to install the insulation on sun facing walls and roof and figure out how to solar power the exhaust fan in upper right rear.

I cannibalized my old shed plywood as much as possible and added 3 wheels to the new base (total of 7). It rolls very easily in spite of much greater weight. The roof is white Colorbond. In my first shed I attached the roof before putting down the Colorbond. This made disassembly very difficult. This time I used an aluminium rail around the roof with sunken bolts in the ply. I should be able to easily take the roof off without removing the colorbond.

The solar project is proving more vexing than I first thought it would be as I cannot yet find an inexpensive controller/regulator that will turn off the fan load when the battery voltrage drops just a little as compared to a lot (meaning the battery will fail in short order). A controller that would disconnect the load at sunset would be perfect but I only can find controllers that turn on the load at night. Any ideas? I'm thinking about building a voltage regulator (12 volts) and powering the fan directly without a battery, but not sure this will work. Any ideas? Fan draws 400 ma at 12 volts and I have a 40 watt solar panel.

http://www.pbase.com/prejto/equipment

Peter

[pluto]

Looks like a good project!

Not sure if this is what you're after but I've got one of these for a project I'm working on which says it will disconnect the load if the battery voltage drops too much (it doesn't say how much though). I haven't had a chance to test it yet but if it doesn't work I'm only out $10,
http://www.ebay.com.au/itm/261392830593

[frolinmod]

You can always use a relay that has both normally open (NO) and normally closed (NC) contacts to reverse whatever you have.

[MrB]

Low voltage cut
10.5V～11V
;)

[PRejto]

If the controller turns the load off whilst charging the battery, then the only way to power the fan is with the battery. I suppose I could have a relay in that circuit in the normally open position. Then at night the load turning on would close the relay and stop the fan. In this situation the only thing on the load output would be the relay coil. Is this how you imagined it?

Peter

[PRejto]

THanks Hugh,

I actually looked at this controller yesterday. The issue here is that the battery will suffer a very short life if it drops on a daily basis to 10.5-11 volts. What is needed is a unit that allows one to set the voltage drop that triggers an "off" condition. The ones I have seen so far are too expensive.

Peter

[mikerr]

Peter,
Isn't that fan already powered by it's own inbuilt solar panel?
I am on the verge of buying the same Solar Fan unit for the same purpose.
Did it not work out as expected?

Michael

[jenchris]

Use a timer, in conjunction with a temp switch.
Both on to operate fan. Either off to stop fan

[strongmanmike]

Pete, that scope(s)-mount setup is..well?..pure astro porn :eyepop:...needs a nice ruuuural setting though :whistle:

Mike

[killswitch]

Jaycar sells adjustable battery cut off kits for like $20-30

[ChrisM]

Further to what Ed said:

The 12V cutouts are readily available from Jaycar as a kit.

They are called “battery saver kit for rechargeable lithium and SLA batteries”, from Silicon Chip, Sep 2013. They come with most of the SMD bits pre-mounted, will handle 30A peak, and are adjustable.

Most of the bits to be installed set the voltage range, then there is trimpot adjustment for the final setting. Cat no is KC-5523 and cost $29.95 each. They are very small - about 38 x 18mm.

I understand that they work very well.
Chris

[PRejto]

Thanks Ed and Chris! I will look into that option.

Peter

[PRejto]

Yes, but it's on the front (hot sun side) of the building. There is another fan up higher on the opposite wall. The problem with the all-in-one fan is that the solar cells won't pick up enough light on the rear of the building. It would be a good roof solution but I wasn't about to cut a hole in the steel roof.

Peter

[PRejto]

Yes, Astro-Porn. With the crap weather and waiting for essential imaging parts it's been about as satisfying!

Peter