light in the north woods

System

Off grid cabin in the north woods (plant zone 3/4). Winter nights 4P-7A. We need reading light and I don't mean dim lit; we are in our 70's and if you are lucky enough not to have the experience eyes get so they need more illumination. At home we use 27W flourescent (150W incandescent equiv.). I can't locate any low voltage lights, such as for boats, with nearly that illumination.
I have 1 SHARP solar module (80W@17.1V = 4.67A and a SUN FORCE charge controller (7A max.; cut out 14.2V; cut in 13V).
Since I need to be able to use a light 6 hrs./ day for 3-4 days without sunlight I'm going to need???
I assume a need to convert to 110V. This will result in some conversion loss; I read about 25%. I assume a need for something to shut off consumption when battery goes below 80%. I will need battery storage; around here a lot of deep cycle lead/acid batteries are used on fishing boats. Would such be suitable?
One week every month is spent at the cabin.
Suggestions anyone? I know physics but every specialty has it's own lingo - even batteries it appears. Thanks in advance

Cariboocoot

Re: light in the north woods

Welcome.

And may I say you've started out the right way by having a target load, even if it is a small one!

You want to run one 27 Watt light for 6 hours per day. That's 162 Watt hours.
One way of doing this is with a small inverter such as this 150 Watt Samlex: http://www.solar-electric.com/sa150wa12vos.html

To supply the power for that you'd need approximately 13.5 Amp hours @ 12 VDC. So a minimum battery size would be something like this: http://www.solar-electric.com/sunxtenagmse.html
Which is slightly larger than necessary.

To charge it you could use your existing controller, as 7 Amps would be plenty. Likewise your 80 Watt panel would be capable of putting out enough current. In fact you could up the battery size a bit to this 42 Amp hour unit: http://www.solar-electric.com/pvx-1240.html and have plenty of power left over, or run multiple lights, or have reserve capacity for dark days.

That's just one solution. I'm sure someone around here knows where you can get DC lights that will do the job. Wait for additional answers.

Cariboocoot

Re: light in the north woods

NAWS has a page of DC lighting http://www.solar-electric.com/thinlites.html but I don't have any experience with these units so I can't say if any would be suitable for your needs.

If you go the AC inverter route you might want to think about what else would make your visits more comfortable. Like a radio/CD player or such. The potential is there.

blackswan555

Re: light in the north woods

At home we use 27W fluorescent

be careful there, "Some" floro`s will use up to twice their rated watts in our language "VA" Have a look at what is written on it, You are looking for something like 110v, 0.5a so is 110 x 0.5 around about 52.5 VA at a guess ?
Tim

Panamapat

Re: light in the north woods

At our cabin, we have a combination of 12 volt LED 3 watt lamps for reading using flexible gooseneck so we can swing the light exactly where we want it when reading. The lamps come with MR-16 Xenon bulbs which we discard and replace the 3 watt MR-16 LED's. This setup works great for task and reading and the flexible neck of the lamp allows you to point it directly to the book or task.

See the gooseneck fixtures here:http://www.sailboatstuff.com/lt_xenoncabin.html#xflexberthlgt

Then use an MR-16 LED bulb like this:
http://www.amazon.com/MR16-LED-Light-white-1230WW/dp/B002L22SLE/ref=sr_1_4?ie=UTF8&qid=1298942586&sr=8-4

We use these style 12v MR-16 LED bulbs and the gooseneck lamps for task and reading lighting in the kitchen, family room and bedroom. We also have 120v CFL for general lighting where we want broad area illumination.

waynefromnscanada

Re: light in the north woods

blackswan555 wrote: »

be careful there, "Some" floro`s will use up to twice their rated watts in our language "VA" Have a look at what is written on it, You are looking for something like 110v, 0.5a so is 110 x 0.5 around about 52.5 VA at a guess ?
Tim

Not really. A watt is a watt. A higher amperage listing just means that the max Amps is flowing during other than the max voltage area of the sine wave. Watts is still amps X voltage, and if a greater amperage is being moved at a lower than the max voltage point, the actual wattage remains as listed.

Cariboocoot

Re: light in the north woods

waynefromnscanada wrote: »

Not really. A watt is a watt. A higher amperage listing just means that the max Amps is flowing during other than the max voltage area of the sine wave. Watts is still amps X voltage, and if a greater amperage is being moved at a lower than the max voltage point, the actual wattage remains as listed.

Actually some CFL's have been found to have rather poor PF with resulting higher consumption. As per this thread: http://forum.solar-electric.com/showthread.php?t=4820

Haven't had any trouble with mine. *knock wood*

icarus

Re: light in the north woods

Test them will a kill-a watt, for VA and PF.

Tony

blackswan555

Re: light in the north woods

Watts is still amps X voltage

Unfortunately inverters do not really work in watts, they work in VA As do generators, Hence you see them rated in KVA then have a power factor corrected KW rating (.9 pf for most gens)
I would suggest a read of http://en.wikipedia.org/wiki/Power_factor
The problem being "Most" CFL`s have a very poor power factor, eg, around 0.50 Which translates in the real world to they use "about" twice the VA,
( V x A x PF =W) Not to much of an issue if they are not the bulk of your system, But in this case, maybe.

Tim

dgsloan

Re: light in the north woods

I would go with the LED light - for reading make sure that you get the right spectrum - the 3000k to 5000k is probably the best for this task. Most flashlights use a higher spectrum blue light so they would not do. If the voltage runs around 6v then the output would be about 500 lumens on the newer lights = this would be about right for easy reading. Make sure that the LED light is properly cooled as a lot of the 12v car lights fail due to poor cooling. If you google "LED reading lights 12v" you will get a number of good hits such as http://www.suite101.com/content/bright-12v-led-lights-for-boat-cabins-light-enough-for-reading-a332468 as a lot of sailboat owners appreciate the fact that less batteries and less generator noise are a big plus in enjoying the outdoors.

bstory

Re: light in the north woods

My husband and I are in our mid-sixties and read a lot so we understand your concern about good reading light. We found these LED reading lights that seem to us to be about the equivalent of a 100 watt incandescent. Since you can aim them and they provide some light out the sides as well as via the spotlight effect, they are easy on old eyes that don't like high contrasts of light and dark. We have two of them in our Sprinter camper van and are about to add two more. Pretty good deal on them at: http://www.sailorsams.com/led_reading_wall_lights.htm. They come in chrome and the "gold" trim shown and more importantly in regular, bluish LED AND the warm white, which we insist on.

They are very low-draw lights

Have fun with your cabin.

System2

Re: light in the north woods

I just found out my problems have multiplied as I looked at a researcher's problems in lower Michigan. My system (battery also) will need to be where Temps. get far below 0 F. Therefore it looks like my charge controller wouldn't work. There is no way to ensure everything will be at 0 or above. I'm feeling the equivalent of bolted.

icarus

Re: light in the north woods

martin wrote: »

I just found out my problems have multiplied as I looked at a researcher's problems in lower Michigan. My system (battery also) will need to be where Temps. get far below 0 F. Therefore it looks like my charge controller wouldn't work. There is no way to ensure everything will be at 0 or above. I'm feeling the equivalent of bolted.

Can you please be a bit more specific as to what problem you are addressing?

Battery capacity drops with temp, but battery longevity rises as the batter temp drops.

http://www.batteryfaq.org/

As for the controller working below zero. My guess is that most controllers will work below design spec temps, but the manufacturer won't promise the results. Charge controllers with battery temperature sensors might not be able to adjust to a fully cold battery.

My batteries and controllers can sit for a several months in the winter in temps close to or below -40 with out ill effect. Batteries in a protected shed or box will self generate some heat as they charge and discharge so that they are likely to be ~ 10F above ambient depending on circumstance.

Tony

System2

Re: light in the north woods

Tony -Quetico Thanks -40F=-40C. Therefore mine 'should' work. Whew! Now to look up the LED info. provided by others. Martin

System2

Re: light in the north woods

Thanks ALL!! I'm amazed at the quick replies. I've got to learn more about batteries since I need very long lasting with little current draw (going 12V LED) and minimum maintenance.
Since most times my solar collector will have more potential than use will that shorten collector life?

Cariboocoot

Re: light in the north woods

martin wrote: »

Thanks ALL!! I'm amazed at the quick replies. I've got to learn more about batteries since I need very long lasting with little current draw (going 12V LED) and minimum maintenance.
Since most times my solar collector will have more potential than use will that shorten collector life?

No. It doesn't matter if you use the panel's full potential or not. Not like batteries whose chemical reactions go on even if they're just sitting on a shelf in a warehouse waiting to be sold. :roll: