Solar light

monseiur

Hi all
Could some one recommend a good quality 12v lights (probably LED) to work off a 12v. car type battery, the battery to be drip charged by a solar panel, this solar panel would have to be designed to charge reliably in Irish winter weather.
Basically I require the light in a stable to feed horses at night (after work) over winter (ESB connection is not an option) 2 LED lights or similar would suffice. I understand that some electric fences work off solar panels, would this type of solar panel be suitable ?...or is it designed for long summer days with long continuous hours of daylight with the sun shining ???
The lights will be on for not more than 30 minutes every evening.
The light fittings do not require a high IPP rating as they will be mounted inside in the stable but condensation may be an issue.
I would also welcome any alternative and perhaps more cost effective ideas that would suit my needs.
Thanks,
M.

I reckon a 20watt panel at about 50° tilt from the deck would get you the required 3Wh through the Winter.

I'd use two 3W MR16 leds with a wide beam angle in IP65 enclosures.

No need for a solar regulator on a 45Ah+ battery but I'd get one anyway.

Don't buy a car trickle charger they're a rip off, get a real monocrystalline module.

I've no idea about electric fence jobbies.

monseiur

Sir Liamalot wrote: »

I reckon a 20watt panel at about 50° tilt from the deck would get you the required 3Wh through the Winter.

I'd use two 3W MR16 leds with a wide beam angle in IP65 enclosures.

No need for a solar regulator on a 45Ah+ battery but I'd get one anyway.

Don't buy a car trickle charger they're a rip off, get a real monocrystalline module.

I've no idea about electric fence jobbies.

Thanks Sir Liamalot for your prompt reply. Can I ask for your opinion on the following :
I have located a supplier in the UK, Solar Power Solutions, they have a 20w 12v. Monocrytalline Solar Panel, price £36.70 sterling and a 30w at £44.77
Their 10a 12v waterproof solar charger controller is priced at £26.48
Considering the low useage, ie. less than 30 minutes every 24 hours - Should I go for the 20w panel without the controller or 30w with controller - or is this an overkill ? As you may have guessed I'm aiming to keep it simple, cheap and cheerful but have something reliable at the same time.
Thanks again,
M.

freddyuk

Does that price include shipping? I would get a 30wp panel from a company that is in Ireland and do not bother about tilting it. Keep it flat and bolted down. You will get more power on dull days if horizontal and it will be less chance of it disappearing. Or you can use anti theft bolt fittings.
Use a 5 watt COB bulb with a E27 fitting. MR16 will be difficult and expensive to install as it needs a completely enclosed fitting or it will fall out. Use a plastic angled batten holder. A COB bulb will give you far more light and you may need only one depending on the size of the area.You will also need a switch and check the cable distance as 12 volt needs bigger cables and short runs.
I would put battery and controller in a plastic enclosure and put this up on the wall where you want the light. Keep all cables short and sized properly.
Small battery bigger panel is cheapest way for this load.

The going rate for PV was €1.20 per watt last time I bought any about 18 months ago. So it may have dropped since.

Solar module VOC 150% your battery voltage.
A PWM controller is all you need, I'm not recommending any cheap Chinese gizmos but I hear the generic Fleabay PWM controllers work alright. Most of the cheap MPPT are fakes.

I'd happily recommend controllers in the > €50 range.

20W should be loads. At the very worst I'd expect that to put 8Wh into the battery in the depths of Winter. It should average ~100Wh in the sunny Summer and ~50Wh in the cloudy Summer.
This includes charge inefficiencies on a half decent battery.

Strictly speaking less than 25W is considered a trickle charge and doesn't require regulation but that's your call, unless you fancy a lot of hydrometer testing and monitoring you're better off with a reg. and you can expand later.

30W is overkill, so is the regulator but better have one than boil your battery dry on the off chance.
Waterproofness may not be an issue so much as humidity resilience.

You need to cable the controller to battery on good gauged cable with less that 0.35% voltage drop for correct charging with 12v.

Actually yeah horizontal mount is possibly better. There is a gain on cloudy days but it's not that significant. Few hundred mA on a cloudy day and longer exposure compared to > 300% harvest when tilted on a sunny Winter day with the sun coming in shallow.

freddyuk

The sun is only "south" for a little while even in winter and we are talking the odd day. So design for dull days not the odd sunny one. You can have 2 weeks of dark days so get a panel that can cover the load under these conditions not a larger battery that will cost more and need replacing.
You do not need an MPPT controller as the cost benefit is not there on a small system so spend a little more on the panel. You can get an encapsulated 4.5 amp quality controller so fine for the wet or a cheaper 5 watt in the enclosure.
You do NOT use a flooded battery especially around animals but a sealed version which does not gas, then it can all go in a small enclosure with controller near the lamp. Even have the switch on the enclosure itself so you only running one light cable and the incoming solar cables.

I think Freddy's suggestions would work best.
The switch doesn't need to be beside the power station.
You could use a relay if it's a very long run, I don't think it would make a huge impact on 5W bulbs.

monseiur

Hi,
Thaks guys for all your advice, it's greatly appreciated.

M.