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.
Tom.
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.
Tom.