Solar powered garage light solution


13 Mar 2007
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United Kingdom
I thought my solar powered garage light solution might be of interest to others here and I’d be really interested to hear if anybody has build something similar.

The problem I was facing is that our garage is not close enough to the house to run power too, but I use the garage frequently enough to really need some light in there.

My key requirements were that the solution would

a) provide a decent amount of light
b) be cheep
c) be reliable

I looked at the pre-made kits, such as the £25 ish Solar shed light type solution that one sees for sale on e-bay / Maplin etc, but a 4W 150mm strip light was never going to provide enough light for a garage! So I decided to investigate a custom solution.

The first challenge was to find a low voltage, high lumen bulb solution which I could run off a 12V battery that would be charged from a small solar panel. The choices were really between LED spot lights (standard MR16 fitting) or compact florescent bulbs which are available at 12V also.

The problem I had with both these options was the expense, to get a good level of light in the garage I’d need at least 4 LED spots which at £5 each (plus fittings) seemed a bit expensive. An 11W compact fluorescent bulbs which ran at 12V would have been the best part of £20 and still only give the equivalent light of a incandescent 60W bulb.

However, I realised that I could get a regular 230V 18W compact fluorescent bulb for £2.50 and a basic inverters for around £12 (e-bay). With the bulb being cheep to replace if I manage to break it and giving me closer to the equivalent of 100W incandescent this was the solution I went for.

This was sounding good, just need a bit of calculation now:

So 18W at 230V draws about 80mA (no problem for the inverter), meaning the 12v supply would need to be 1.5A.

Lets say I wanted the ligh to last for at least 2 hours a day, meaning I would need a 12v battery with a minimum of 3 Amp hours. However, we need to factor in a 20% efficient reduction for powering the inverter, so lets say minimum of 4 Ah.

It never hurts to have a little extra storage capacity so I went for a 7.2Ah 12V sealed led acid battery which would cost me around £10 (trade).

Based on 10 hours of usable daylight per day, my solar panel would need to produce 12V at 400mA which would be 5W. Well I found a 5W solar panel on e-bay for around £27 (delivered), seemed reasonable.

One week later, the solar panel and inverter arrived from my e-bay distributors and I started to put the whole thing together. As well as a few meters of flex to wire the whole thing up I need a light switch (re-cycled from an old project) and a basic pendent light fitting (£1 added into a screw fix order for work) and we were good to go.

Actually installation took less time than designing the project and sourcing all the parts, and it was simply a case of wiring solar panel to battery, battery to inverter and inverter to light via light switch (on the live), simple really ;)

I did have to build a frame to keep the solar panel at an angel and to enable me to weight the whole affair down on the garage roof. Also after some testing I moved the switch from the 230V side of the inverter to the 12v supply side as I discovered the inverter was drawing something like 100mA constantly if left connected to the battery with the light off which was rather a waist.

But that was it, garage is now well lit (glad I went for the 18W bulb not 11W) and whole thing cost around £50.

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Wiring diagram, pics will follow.

Does there need to be anything in the circuit to prevent the battery being over charged?
RF Lighting said:
Does there need to be anything in the circuit to prevent the battery being over charged?

British sun light ? But a valid point. I would be more concerned about no fuse in series with the battery.

And I would have used 12 volt caravan / car type lamps which might be more efficient than the invertor to mains method.
This is a great idea - is there anyway to secure the solar panel? My garage is just around the corner from my house, we are in a cul-de-sac and have no probs with theft or anything but I'd like to make sure the panel can't be nicked!
Robzc, am lucky enough to have been able to position it out of view of passers buy so I haven't' secured it. But the frame has locations for fixing so you could fix it to a wall or frame with security fixings.
i like it (but yes do add a fuse).

now you have had it up and running for a bit have you tested how much light (time wise) you actually get this time of year?

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