I want to set up a 12v lighting system in a outbuilding, possibly with a
12v battery to be topped up by a solar cell. The system will need to provide light for a 4m x 4m room, for an hour or so a day.Anybody got any suggestions?
What level of light is required? Just enough to read by? Enough to do detailed work? This can make a huge difference.
An 8W 12V fluorescent tube will provide enough light to see, but nowhere near enough for say a workshop.
Sorry, I should have said. This is a stable, so enough to see the horse! I was thinking of around 40W of tungsten, so I think an 8W fluorescent tube would be ideal.
But where to get one to run from 12V, what size battery, how to re-charge, and what sort of cable and switching?
Nigel M brought next idea :
It really depends upon how much light you might need. You can buy 12v light fittings as used in caravans and for camping, these are fairly efficient consuming 8 to 12watts each. Alternatively you might consider the 12v quartz lights with built in reflector, which are normally run from a transformer in domestic situation. These can be obtained in
20watt and 50watt versions.Obviously the higher the wattage used, the larger the battery would need to be and the solar cell to recharge it. In addition you might need a control on the charging system. For what an adequate solar cell and battery would cost, you might find that running a mains supply would be the cheaper option.
Halfords. Or any other similar car place. Together with a motorcycle battery and a small charger.
All our stables have a pair of 13W CFs each. This is plenty.
Don't use tungsten - waste of energy.
Ok, you need a light, like this:
Then you need a car battery. They are well suited to this type of application, where they don't get fully discharged. Local scrap yard is a good place for second hand ones (£5 each), or any motor factor.
Then you need a solar panel. A weatherproof one is a good idea, and if it doesn't have a diode built in, you need to add one. Tjis one is ideal:
Then you need some cable and a suitable switch. I'll leave those for you to figure out ;-)
Nigel M presented the following explanation :
Any caravan or outdoors type of dealer would have the complete tube and fitting for £10 to £15. They would also probably stock the type of battery you need, a type intended for deep discharge rather than a car type battery.
Simply wire in twin flex (the smallest size of mains flex is adequete) from the battery positive (+ve) via an in line fuse of 5amps to both the + of the solar cell and one terminal of a switch. From the second terminal of the switch to the + of the light. The negative (-ve) of the battery needs to be connected to the -ve of the solar cell and the -ve of the light.
Black = -ve, it is conventional to use the blue in the flex for this. Red = +ve and it is convention to use the brown in the flex for this.
Almost any switch can be used, but probably a pull cord switch as used in a bathroom might be best. Any DIY store would stock these, as would the electrical wholesalers.
Remember to vent the battery to the outside - you don't want a shed full of hydrogen.....
May be worth looking at one of those 'portable power' type devices, containing a battery and charger that you occasionally see in cheapo shops, but remember that lead-acid batteries DO NOT like being left flat for long, so you must remember to charge it regularly. Solar would be ideal if you can get enough capacity at a sensible price. The sort of places that supply to boatowneres would probably have everything you need, but at a price. Surplus solar cells are sometimes findable cheaply. Never forget ebay.co.uk as a possible source for this type of thing.....
Jsut bought 3x "emergency" lighting units to use for lighting a cantina (call it a barn or stable if you wish). These were twin fluorescent lamps with a rechargeable batterypack and a very neat mains lead and 13A plug housed in a compartment on the back of the unit. Each has 2x18W fluorescent lamps giving a good light output and can run for about 1.5 hours on battery. They are switchable for either or both tube in operation and can be set to switch on automatically if mains fails.
They cost me £10 + VAT (£11.75) each.
The actual model is here:
Similar unit here:
There's no need to get a deep discharge type for 8 watts for an hour. That wouldn't even scratch the surface of the smallest car battery. If the solar system works properly and keeps it topped up. I'd expect a car battery to have a longer life under these conditions than those it's designed for.
I've done a similar thing in a rented council garage with no mains power. I originally used 3x 50w 12v bulbs but these were pretty dim and drank power. Current consumption was over 12 amps.
So, I swapped these out for cheap 20w CFL's (similar to 100w tungsten each apparently) and used a cheap mains inverter from maplins to power them. Result = far more light and far less power drain. I modified the inverter to extend the on/off switch to an extrenal wall mounted light switch. It's powered from a 65ah leisure battery and a solar panel bought on ebay - can't remember power rating but about 1'x3' in size. Panel is fitted to garage roof and system has been operational for over a year so far with no problems. Inverter based lighting system has added bounus of low current mains in garage for small tools or radio etc.
Alan.
I think I may have underestimated slightly. The unit from Maplin looks ideal, and there are two stables. So assuming each 18W unit takes around
1.5 amps, then this is 3AH. I don't see how a, say, 120mA solar panel could replenish this. Or have I misunderstood something?That's the answer I wanted, I didn't think cable was correct.
Surely there are normally only for use with AC. I would have thought that a fluorescent lamp would present an inductive load to a DC source, so wouldn't this mean I needed a special switch?
Fluorescent style camping lights are far and away the most efficient thing to use.
Camping stores and caravan places.
Amps is only an amp at best, so cable is easy. normal T & E can cope with that.
What size battery? Well a standard car battery is about 30-70Ah, so for an hour a day you should get a month out of even a small one. Halfords?
Charging 0- well you could jump lead it from the tractor or whatever and leave it running for an hour or two every month on tickover.
If it were me, I'd run an extension cable temporarily and leave it on crappo charger overnight every week to be sure, or possibly get a battery with handles or on a trolley and get two of them, and have one on charge and one in use, and swap them every week or so.
I am sure on this sort of duty cycle solar panels woud work or windmills, but the cost....
>
Not really, no.
That's an expensive and inefficient way to do it - unless you also make use of the 230 volts generated for other purposes. 12 volt DC florries are cheap and readily available.
They don't give a DC rating for this sort of switch purely because that application would be so rare. But in general, most 230 volt AC switches will happily work at the same current rating on 12 volts DC.
If you're really worried, you could use a 20 amp shower type. ;-)
This is a good idea, the other could power the electric fence once it was charged. Much cheaper than solar power.
How far is the nearest mains? We have hundreds of metres of 12V cabling (all done in very cheap T&E) supplying things like electric fencing.
About 75m to my house, but over the road.
We've suddenly got a plague of reactive road warning signs popping up all over the county. They are all on long poles with a windmill on the top and solar panel just below. If the council are using this technology then it must be at a price where it starts looking good for other uses as well, presumably the stables would be in a position to get a good dollop of the available wind and sun?
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.