emsfactory
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| posted on 30/3/11 at 09:34 AM |
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bathroom lights off a car battery?
hi all,
just thinking out loud here.
Looking to change the bathroom lights to downlights and started looking at leds.
Would it work to say have 4 downlights running off a car battery, or a deep cycle set up with a small solar panel on the roof to keep it topped up?
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coozer
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| posted on 30/3/11 at 09:39 AM |
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Now then, I have couple of batteries lying around the garage and in order to keep them charged and working OK I was thinking exactly the same
thing.
Small solar panel charger thing and a couple of 12v down lighters to keep the things cycled.
I look forward to the knowledgeable responses
1972 V8 Jago
1980 Z750
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dhutch
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| posted on 30/3/11 at 09:45 AM |
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Carnt see why not.
Most LED units come with internal voltage regulation which can cope with a fair range of inputs. Unlike 12v domestic halogens which take a dim veiw of
running of a lead acid at 13.8v (or even 15v of so with engine/alternator/charger running) rather than a regulated 12v.
Obviously it would be for fun rather than serious elec saving, if its just a set of LED bathroom lights, but why not! go for it.
Daniel
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hughpinder
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| posted on 30/3/11 at 09:56 AM |
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We rented a villa in the south of spain that ran all its lighting (LED) from some solar panel and batteries (it was miles from the grid). It worked
well for us, but you did have to be careful to switch lights off all the time. It ran off about 1 to 1.5m2 of panels and 2 85Ah batteries and was ok(4
rooms in the place we rented), but they get a lot of sun compared to us!
The main problems I see
1. No idea if building Regs are satified if you ever sell up:
2. that even doing this, the batteries will have a finite life of (say) 10 years, and the panels/charger of (say) 20 years. You definately won't
save money. Mains powered low energy or LED bulbs are relatively cheap and would just plug in the normal mains and have next to no maintenance.
These are the 240V 1.5W led lamps I'd get:
http://www.screwfix.com/p/halolite-blue-led-lamp-gu10-22lm-1-5w/29860 - very long service life on them
Regards
Hugh
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tegwin
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| posted on 30/3/11 at 10:32 AM |
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Thinking about my bathroom.
I have 5 3w LED downlighters. This provides an acceptable level of even spread light. 5 1w LED downlights I dont think would be sufficient, unless
you like dull rooms. I do use some of the 1W ones in my understairs bog, its just about enough for sitting and doing your work, but not enough if you
want to put on makeup or read the paper etc...
Ok, you could get away with 4... so thats 12W@12v which is 1Amp.
Assume you have an "average family" where the bathroom is used after dusk every day for 3 hours. (more during winter when its dark
earlier, less during summer...)
That is 3 Amphours a day.
Or 0.024KwH per day.
Assuming a 40Ah car battery, you could run for about 10 days without charge.
For charging the battery..... We will assume an average daylight of 8 hours across the year. The efficiency of an average solar panel is about
20%.....
Given that solar insolation (incoming solar radiation or energy from the sun) for the UK is on average about 3kWh/m²/day.[worth noting that this can
vary from 1 up to 5 depending on how far north you live and what the weather is doing]
(dont forget the wee poor efficiency) which means you can actually harvest only 0.6kWh/m²/day for a good panel.
That means, in theory you would need a panel that is about 400 square cms or a 20x20 panel. However..... You will get tremendous loss through the
battery charger and battery internal resistance... further calcs would need to be done to work out how much bigger the panel would need to be.
The flaw in this of course is, you need to use the lights for longer in the winter when there is less sunlight...
As far as building regs goes, I cant see how/why they would object, provided that the lights worked.... to be on the safe side I would use a charge
circuit that triggers a mains supply if the battery runs out.... would protect the battery and ensure you never have no light....
I would also fit PIR/light sensative auto light switches so the lights are only on when needed....
I dont have solar, I use a switch mode transformer and a PIR/light sensative switch fed from the mains... solar panels and chargers are too
expensive...
Dont base any decisions on my maths without checking it :p
[Edited on 30/3/11 by tegwin]
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Would the last person who leaves the country please switch off the lights and close the door!
www.verticalhorizonsmedia.tv
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montythemole
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| posted on 30/3/11 at 10:41 AM |
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Have also considered this, but more for hallway lighting etc so you could run a photocell as well and have them come on at dusk as security measure.
Also in event of power cut would have enough lighting not to panic the kids etc. I may be talking doom and gloom here but we are seriously facing an
energy crisis (old plants at end of life, renewables not delivering (I work for one so I'm not biaised) new plants delayed) made worse by the
only viable new source (nuclear) getting bad PR in Japan and I can forsee limited hours and blackouts on the horizon so could be very useful in
time!
Buildings regs wise I think you're fine as separate from the mains installation. Same way a massively overloaded shed running on four
extensions leads in a line into the house socket is 'OK' since not a wired in part.
I also considered running a few USB charging points off the system as well since pretty much everything (Ipad, Iphone, Blackberry, sat nav, vid
camera) uses USB charging nowadays.
1985 Dutton Phaeton Series 3 1300GT
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emsfactory
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| posted on 30/3/11 at 11:13 AM |
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I was thinking about the mains driven led type. That way if it doesnt work or i get fed up I can just switch them to mains.
I am dealing with building control just now for a shed and that is fun enough. Dont think i'll trouble them with this.
I know this is only very small and really only for fun/experimenting but leccy is not going to get cheaper.
Yes it'll save some carbon blablabla but i like the idea of saving money. Or spending the same but it not going to the power suppliers.
This wont save anything I know its too small but I have been looking at a large solar system, with the feed in tarifs. It all sounds too good to be
true.
This could be a nice little experiment as I have not yet had a play in this area. Anyone using a large solar set up?
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hughpinder
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| posted on 30/3/11 at 11:43 AM |
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My Dad has a 30m2 PV array. It was installed about 14 years ago and has given no problems in that time. He was lucky in that he has a triple garage
and the roof angle was at the ideal pitch and south facing. When he had it done this was about 30k set up, but government grants paid half. Current
cost for such a set up is about 12-15K. It has given almost 300kwh in the best ever month, usually about 200kwh/day in the summer and about
50kwh/month in the winter. Modern panels are supposedly a few % more efficient, but not a lot, and it'll also depend on mounting angle. Average
annual electricity is about 1900kwh/year (5.5kwh/day). With the feed in tariff being much higher rate than you buy back at, for new installations, you
can probably wipe out your electric costs even if you are a higher than average electric user (average uk house 12-20kwh/day depending on family
size/kids or not, and which surveys you want to believe).
Hope that helps
Hugh
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montythemole
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| posted on 30/3/11 at 03:20 PM |
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We've looked into large scale PV as well at home (well large compared to a bathroom light). The figures are very good and a better return than
you'd get sticking your 10k in an ISA. The downside is it does tie your money up so if you suddenly see a great deal on a car or something you
can't empty your ISA and buy a TVR / dream cruise / wedding.
Still not committed to it just yet as prices still dropping on the installation. We've had quotes as cheap at 7k when we started with nearer
15k quotes. I work from home so would be ideal as I use a lot of expensive daytime leccy, just with two kids and too many cars we've not had
time to sort it.
1985 Dutton Phaeton Series 3 1300GT
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Ninehigh
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| posted on 30/3/11 at 07:00 PM |
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quote:
Originally posted by tegwin
I would also fit PIR/light sensative auto light switches so the lights are only on when needed....
Now that's an idea, that would save us a load of electric as the kids have to have EVERY light on even if it's the middle of the sunniest
day ever
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David Jenkins
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| posted on 30/3/11 at 08:16 PM |
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Ordinary car batteries aren't much good for this sort of use - they're designed for short bursts of high output (starting the engine) then
continuous use at or around their nominal voltage. If you regularly discharge them right down then they will fail quite rapidly.
The best batteries would be the sort used by caravanners - usually described as "deep discharge". These will not be spoilt by regular
discharge right down to their minimum.
It's horses for courses - deep discharge batteries are rubbish as car batteries!
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Krismc
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| posted on 31/3/11 at 07:28 PM |
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I use 2 off these at work with a standard 240v trickle charger to power lift lights 12 x LED fittings and they last hrs if power goes out, lot cheaper
than a EMU and a lot safer.....
I use with a standard charger normally, but have set up 4 with a wind turbine to power a electric fence and a single halogen light and also fitted 2
batterys and a solar panel in a caravan too power a powered 3rd wheel.
Got plenty of these batterys and chargers to go with them if anyone needs any??
[Edited on 31/3/11 by Krismc]
Built, Ivaed, Drove and now Sold - 2011 MNR VORTX RT+ 2000cc Zetec on R1 Throttle boddies.
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