Off Grid DIY solar powered Shed Lightning

[Deelirium]

Hello all,

Seeking some advice on a setup i am attempting to design.
Recently finished construction of a horse shelter/feed shed and require to have internal and external lightning for it.

It measures 8m by 4m (26'*13' approx) and is divided by an internal wall half way to make 2 bays of 13' by 13'.

One half will be used simply as a open access shelter for the horses and requires no more light than to walk by, the other will be a feed storage/mixing station and requires a bit more illumination, within this will also be a workbench. A few flood lights on the outside of the building would be required as well.

My current thinking is a solar panel (mounted on roof) with deep cycle battery. All the lights i plan to have operated by a manual switch and most likely wont be used for any more than 1-2hrs per day.

I been flicking through a few different ideas including LED strip lightning, caravan lights, Outdoor floods lights, individual leds mounted on heatsinks etc. but struggling to find too much relevant information from recent sources. Looking for more information on what people would recommend is the best approach as well as including possible sources and specific sources.

I am a competent tinker and wont shy away from utilizing raw components if it will build a better system for less.

As always the less spent the better, but the light needs to be fairly good as it is primarily for my father who has less than ideal eye sight.

Any ideas and recommendations would be appreciated.

Cheers,
Deelirium.

 

[SemiMan]

Where in the world are you located?

What you are looking to do is pretty reasonable if you don't try to scrimp on every penny.

This sounds like an unattended installation so I would recommend a good quality AGM battery (or LiFeP04). Normally I would say flooded for solar, but only if you are prepared to do the work to maintain them.

The most efficient lights will always be best for solar, but LED strips work pretty well, and given the ease of use at 12V, may be best.

Let's start with:

- Where are you
- Will the panel be shaded at all

and go from there.

 

[Deelirium]

Thanks for the reply.

Located in Tasmania Australia, fairly well *** end of the world. Purchasing will mostly be from online avenues.

The panel will be located in a very sunny spot with clear surrounds and should get the best from the light available. In winter it would still get a pretty good strong 5+ hrs of sunlight That in mind i will most likely be leaning towards designing it to cope with 2-3 days of overcast days.

My father gets a good trade discount with Bosch batteries so will most likely be going with them. AGM most likely. the smallest they come in is 12v 60AH which is most likely what we will be using.

 

[SemiMan]

Thanks for the reply.

Located in Tasmania Australia, fairly well *** end of the world. Purchasing will mostly be from online avenues.

The panel will be located in a very sunny spot with clear surrounds and should get the best from the light available. In winter it would still get a pretty good strong 5+ hrs of sunlight That in mind i will most likely be leaning towards designing it to cope with 2-3 days of overcast days.

My father gets a good trade discount with Bosch batteries so will most likely be going with them. AGM most likely. the smallest they come in is 12v 60AH which is most likely what we will be using.

Well then! ... this makes things easy .... almost

Count on at least 3 days overcast ... even in Australia, and where you are, that may not be enough.

Let's go with really really bad worst case.

LED strips, 75 lumens/watt.

2000 lumens total.

You need 27 watts.

Let's say you love this so much you are out there 3 hours per day on average (I would consider investing in a motion detector).

That means you are using 81 watt hours / day.

12V, 60AH = 720 watt hours (approximately). Let's consider a battery near end of life, so 80%, or 580 watt hours.

I understand it actually can get relatively cool where you are, so let's say 20% reduction in battery capacity in winter temps, so now 0.8 * 580 = 470 watt hours.

Last but not least, let's never let that battery get below 20% state of charge, so 0.8 * 470 = 370 watt hours.

370/81 = 4.5 days of storage .... we should be good ... but ....


Looking at the climate data / solar data for Tasmania, there is quite a range. You are not in one of those areas that gets a lot of overcast and rain in the winter are you?


So back to that 81 watt hours/day. Count on 70% panel efficiency (voltage mismatch, dirt, etc.) and 85% battery efficiency, so you would need 135 watt-hours/day of panel capacity.

Looking at the solar data I have for Tasmania, again, quite a range from 2 peak sun-hours/day to 4 peak sun-hours/day in winter depending on the location. Let's call it in the middle and hope we are right and say 3. 135/3 = 50 .... rounding up ... since solar panels do degrade with time.

Given your usage, all should be good.

Here is what I suggest

- Stick with the 12V, 60AH
- Buy a good, i.e. Morningstar charge controller. No need for MPPT in this case. Get one that is 10Amps, like a SunSaver 10
- Get a 100W (12V style) solar panel. It will be big, but you will never have to worry. Alternately start with 50W, then add another later ... or got 65W or 80W. A bigger panel will charge the battery faster which AGM batteries like.
- Get some good quality LED strips and note what the efficiency is (and current draw) .... and work out how much power you are drawing. Measure it if you can. Add strips till you are satisfied with the results keeping in mind what I put above.
- Consider investing in a 12V motion detector .. but note they do have some power draw, all the time

One suggestion I will strongly make based on where you are located is to buy a case (or plastic food cooler) big enough to hold the battery, and bury the battery in the ground. Alternately, at least put it in a half decent insulated plastic cooler. The battery has a lot of thermal mass, but only so much. Lead Acid batteries rapidly degrade over 35C. The also lose capacity when cold. Burying it or at least putting it in a cooler will reduce the temperature extremes giving you longer battery life and better capacity.

Semiman

 

[Steve K]

That's a really nice, very thorough reply from Semi-man! Well done!

on the subjects of motion detector switches... I've seen little battery powered lamps that use PIR motion detectors and don't seem to consume any power. My knowledge of PIR motion detectors is largely limited to a video from Dave Jones on his EEVblog, which suggests that the PIR element itself shouldn't be consuming any power. Does anyone know of a low cost version of these elements? I did a search on Digi-key or Mouser some time ago and was surprised at how expensive they were (IIRC, of course). Any recommendations for one in low voltage applications (5 or 6 volts)?

 

[SemiMan]

You can get them for a few dollars on Ebay. No comment about the quality. 5V versions from Panasonic on say Digikey are $5-10 from memory. They likely work better though. Power is low, few 100 uA or less depending on the model. You need a FET or something to switch the lights on/off. I am sure there is something on Ebay with a relay as well.

I have used the Panasonic ones .. very good and very stable over a wide temp range. When you need it to work, they work.

I am sure there are enough battery powered motion lanterns out there that you could tear one apart too. That may be cheapest.

 

[Deelirium]

Thank you very much for your very informative post.

Where i am situated is more on the upper end of the spectrum of light exposure (3.5hrs according to the meteorology) in the worst of winter. And temperatures very rarely get above high 20s and in winter hover around 0-4 at night and 8-12 in the day.

So if strip lightning is a good avenue to explore, what determines a good quality strip light? from my few poking around there is a great disparity in pricing with little details on them (plus little knowledge of how accurate those details are. Eg Lumens or Chinese lumens)

Was thinking of going with around a 80 watt panel to begin with so i would say that is what ill do. Maybe go a 100-120 if i find a good price.

Thank you again.