A mate of mine has just given me 10 sealed lead acid batteries 12v 10w with a the correct charger and i was thinking i might be able to install low voltage lighting in my garage as i have no mains supply nearby.Has anyone else tried this and do you have any advice on what type of lights to use that give a good output at reasonable consumption rates.

Just one normal 12V halogen bulb consumes 20W/hour. This is for a spot effect - you need a flood effect. But using your figures - you'll have enough for ermmm 5 lights which would in no way be enough. Sorry!

Course - I have been known to be wrong... someone may correct me later!

[Edited on 25-10-04 by Hellfire]

Thats about what i thought,i,ve had one 20watt bulb on one battery for 3hrs and its already starting to dim and puts out nowhere near enough light.
I thought the low voltage strip lights used by caravaners might be better but i was looking for this kind of advice before wasting my money(i already have one money pit)

[Edited on 25/10/04 by ray.h.]

caravan lights are about 20 quid a chuck for 20w or so. still not really bright enough.

why not spend 80 quid or so on a small generator?

or get a couple of car headlamps and cbounce the light off the ceiling - or you will get dazzled - you can power these off your donor / build car battery

atb

steve

[Edited on 25/10/04 by stephen_gusterson]

I dont understand watts/hour etc ,but I do know in the several motorcaravans I've owned ,I have always used those transistorised 12v lights ,(2 or 3 on at once), usually for most of evening , and havent had any starting probs on batteries next day .(also have run a small tv,and powered elec. shower pump etc )

I've got a generator for sale ,smallish ,won't power a welder though .Will dig it out and get make,model etc if interested.

Ive already got a big F...off generator but it is noisy and smelly and the neighbours don,t like it at 10pm,but thanks for the offer.
I assume caravans and campers run off a car battery off say 45-55 amps so it would be possible to run 4x10 amps to get reasonable duration.Even one decent spot light to illuminate the work area would be acceptable?
also how do you calculate the life of a battery if you know the amps supply and the watts consumption?

[Edited on 25/10/04 by ray.h.]

Most batteries are labelled in Ampere-hours. So, if you have a 100A/H battery and run a bulb that takes 1 Amp, it'll last for 100 hours, 2 amps 50 hours, and so on - allegedly! In reality, the more power you take, the lower the ampere-hour rating becomes.

P (watts) = I (Amps) x V (volts)

...if that helps!


David

[Edited on 25/10/04 by David Jenkins]

if you can get hold of a leisure battery, they have a lot higher Ah (ampere hour) rating than car batteries, some over 100Ah. take for instance a 50 Ah battery, it can supply 50 amps for 1 hour or 1 amp for 50 hours.

The power of your lamps, in watts is the energy they consume every second, in joules.

since power is the product of voltage and current (P=VI) this gives you the overall power draw of your system. i.e rig it up, then use an ammeter in series to give current and volt meter to give the power consumption of the system

i'm tying my mind in knots. let me consult the books and get back to you. it's been nearly 6 mths since i did my a levels and havnt thought since. duuuuuhhh the top bit stands anyway

tom

beat me to reply david

[Edited on 25/10/04 by indykid]

I understand that bit but most bulbs are rated in watts and don,t tell you how many amps they consume/hr.
Srry i was typing when you posted.

[Edited on 25/10/04 by ray.h.]

Apply a bit of basic algebra to the formula!

I = P / V

So, if you have a 24W bulb

I = 24 / 12 = 2 Amps.

David

So watts(20) divided by volts(12)= amps (1.67) so a 10 amp battery should last approx 6hrs


Einstein watch out.

[Edited on 25/10/04 by ray.h.]

If you mean 10Amp/hour - correct!

However, you may get less - A 10Ah battery is pretty small, probably designed to last a long time while giving out smaller currents - don't be surprised if you only get 4.5 - 5 hours.

David

yes, thanks for that guys. i've gone back to my folder, and checked all my formulae, gone round it both ways to make sure and yes, it's all good.

christ, you wouldn't have thought i had just got an A in a level physics. I can tell you all sort of irrelevant crap tho. anyone want to know about red shift or the field pattern inside solenoids? i can do you a good line in hysteresis loss and the like also. no takers? i suppose thats why i didn't go to uni. how much more useless stuff can you learn without turning into a techie freak

tom

Just a thought - if all you want is a spotlight, then make sure that your bulb is in a reflector - a little bulb that looks feeble out in the open can look really bright with a silvered reflector and lens.

Have you considered canibalising an old 12v torch?

David

spot source lights are hard on the eyes to work with.

id suggest something with a more diffuse light.

ive got one of those portable 500w floodlights. its fcuk ing useless. if it points away from you the lights not where you want it. if it points where you want it, it nukes your eyes.


how about a standard 240v strip light - powered by a battery to mains converter / inverter?

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&category=15263&item=2496954017&rd=1

atb

steve

ray, is there not a lamp post nearby you can tap juice from?

alternatively, ask the neighbours if they want to invest in a huge tesla coil. that way you can have fluorescent lights running and they need no connections. they get their energy from the electric field. a slightly elaborate solution, but tell them they have to or it'll be back to the generator

tom

[Edited on 25/10/04 by indykid]

Decision now made. A spot light with a fairly difused spread on a tripod so i can move it around.2x10amp batteries should give me an evenings work just and i can keep plenty of spares on charge.That should do for now.
So where can i buy a Tesla Coil?

Another solution could be to pop into your local Maplin store (you've got one in Stevenage) and treat yourself to an invertor. These devices will convert your 12v DC into 240v AC mains, if it's just for lighting then one that supplies 150W would be sufficent. (About £20) The real advantage in doing this is that you can use low energy 240v lamps, giving you a lot more bang for your buck. A couple of 11w lamps should suffice, I think these will draw about 2 amps from your batteries IIRC.
You could also have a look at their solar panels whie you're there.....!

I'd say the same. Invertor, domestic strip light, and a car battery. I used to do this before I had mains in my garage. Used to last a couple of hours, even on the knackered battery I was using!

Failing that, I saw some white LED lights for sale in B&Q the other day. They will run on 12v and are stupidly efficient (I'd guess 85-90%, as opposed to 15-20% for incandescent bulbs)

Chris

You could always connect 2 car batteries (or whatever kind) in parallel. (+ve to +ve and -ve to -ve then take your normal 2 wires from one battery.
You'll get double the Amp/Hrs and keep the same voltage.
Don't connect them in series or you can kiss your 12v bulbs goodbye.

Ye,iknow i need to put them in series but it still needed to be said.
I hadn,t considered an inverter untill now cos i thought they would eat batteries like smarties.
Inverter and low energy bulbs looks very promising,off to Maplins tomorow to price up the bits.This could be idiot proof.
And before any one else says it,IT NEEDS TO BE!
Thanks one and all, i,ll let you know the end result.

I'd go for the inverter and strip lights. PLenty of lovely white paint... floor walls and ceilings!!! Even paint your chassis and body white to reflect as much natural/emitted light as possible. Could you put translucent roof on garage?

HTH

Or look HERE

Ray,
If you,re going to Maplin check out item N64AU, 150w invertor, £29.99. You won't need a pure sine wave jobbie for what you're doing, a standard invertor will work just fine.
They've actually gone up a bit in price recently, about a year ago I bought a 300w unit for about 20 quid. They're often on special offer tho' if you need to save a few quid.

[Edited on 25/10/04 by G.Tyler]

80 sovs did sound a bit steep for a bit of light, 30 sounds much better.

[Edited on 25/10/04 by ray.h.]