Portable Solar Powered Lighting

[GeoJohn]

I recently got a request for expert advice on installing a battery and flourescent lighting in an enclosed trailer used for camping. (Never tell anyone you are an Electrical Engineer, or you will be asked for that sort of help, I am an Embedded Electronics Engineer from now on.)

This is the application: A scout troop owns a very nice enclosed trailer in which they use as full time storage for all of their camping equipment such as tents, cooking gear and other scout type stuff. They set up a cooking area outside for adult and troop meals. They want 1 or 2 lights in the trailer that operate on a switch and will be only used intermittently, and approximately 5 lights to mount outside under a tarp. The outside lights will operate 4 hours a day for up to three days. The trailer is used approximately every three weeks.

My suggestion was to get a deep cycle battery and charge it after each trip and top it up before. I could not recommend flourescent lights because it has been a very long time since I explored that technology. They want to go with a solar panel on the roof of the trailer and avoid the charger completely.

Can anyone suggest a source for decent 12 volt flourescent lights, and offer advice if the wattage rating is actual power consumption or the bulb rating? Also, a source for solar panels that can be mounted on the top of the trailer and not get destroyed by bouncing and flexing would be great.

I really would appreciate advice from someone who has set up a similar system in a boat or cabin.

(A short story: About 15 years ago, I lived in a cabin that I powered with a deep cycle marine battery. I had one 12 volt flourescent drop light purchased from an auto parts store, and a laptop that would run directly off 12 volts. I would occasionally carry the battery to a neighbor who had a lawnmower/alternator charger in his barn. He charged the batteries in his house through two Romax cables that ran about 80 feet under the driveway. When he needed to shave, he would go out to the barn, start up his big Onan welder and shave with his electric razor. I'm glad I am on the grid.)

[Norm]

  Why not use a pedal powered generator to charge a battery? Half a dozen young scouts taking 10 minutes each ought to be able to charge a battery the power that one or two 15 watt ...12volt compact fluoresents light bulbs consume can easily be replaced.

  Using 2 batteries...they could recharge one

battery while the other was being used to run the

lights....it wouldn't be advisable to run the

lights directly from the generator....unless you

had a really good voltage regulator...which would

then complicate things.

  The whole thing including batteries shouldn't

cost more than $150.

               ( :>) Norm.

[Bruce S]

I'm with Norm on this one.

The pedal power is going to be way less expensive than the solar panel.

There are websites that carry "rollable" solar panels but they are not as effiecent and costs can be high.

I too would go the 2 battery route and let the scout help with the energy production. This way they could use that experience towards a merit badge of some kind.

You could even put a meter in series with the genny and they could have trials to see who can produce the most power in a given time period or last the longest.

There are earlier posts in the lighting section about how to even convert AC units to work off DC power. Not too hard to do either, few parts, and can be customized to fit the trailer. Do a search for DC floos.

Good Luck and Happy trails.

Bruce S

[ghurd]

I have set up a bunch in barns. Does that count?

About the CFLs. Some are better than others.

The 12V 11W Solsum I use actually uses 0.920A, just like the box says.

Those cheap $7 12V tube drop lights rated at 15W(?) only draw about 0.550A, they have a VERY short life span, and are just gennerally junk.

Our hosts have some 12V CFLs.

A jelly jar type protection would be a great idea.

Uni-Solar made a US-32, 32W PV, 1.96A output. I'm not big on the thin-film technology or the company, but they take flexing, bouncing, and impacts quite well.  About $210.

They just stopped making anything under 60W, so if that seems like a good choice, order one soon!

A good small controller is the Morningstar SG-4, about $30.

Intermittently, in the trailer, maybe a #1156 (2.2A), or a #1141 (1.5A) auto bulb.

Fluorescents don't like short cycles.

A deep cycle battery about 100AH should be good.

I really like Norm's idea about the treadmill motor and pedal power!

Low cost and fairly easy.

It would teach them how much work it takes to make a bulb operate.

Burn some of the S'mores sugar.

All just 2 cents,

G-

[Nando]

First you need to calculate the power usage.

7 lamps, fluorescent 10 watts each would be 70 watts/hour times 5 hours = 350 watts/hour times 3 days = 1050 watts/hour plus efficiency, let's say 80 %, so it would be 1050 / 0.8 = 1313 watts /hour and if you use a 12 volts setup then the size of the battery would be 1313 / 12 = 109 amp/hour therefore you need to have a battery with at least 200 amp /hour for battery life and power reserve.

If you have a solar panel to charge the battery, let's say 3 days, then we need to assume that the power daily requirement would be about 400 watts or 33 amp/hour per day and assuming 5 hours a day charging then 33 / 5 = 6.6 amps needed, so the panel would be a one 12 Volts @ 6.6 amps or 80 watts panel; a 75 watts panel will do.

You will need a good charger capable of MPPT to optimize the charging, also, I recommend that the trailer when connected to the tow auto to have a connection to charge the battery as well -- it will do wonders.

Truck and trailer stores handle the fluorescent lamps, some quite good ( 20 to 30 dollars), look for the 10 or 13 watts which represent about 50 to 60 watts resistive lamps, also for emergencies, Home Depot carry some small lamps, I think 8 watts, I have one that give good light and cost around 10 dollars, I have installed NiMH AA batteries in it with a charger connected to the external power plug.

If you need more assistance send a message to nando37-at-comcast-dot-net

Regards

Nando

[ghurd]

They are only using the trailer 3 days or less every 3 weeks.

[Nando]

Though 3 days every 3 weeks Murphy says that once you finish putting everything together and tested the trailer is going to be used for 8 days straight.

1. ) You could get a connection to the tow truck to charge the batteries.
   
2. ) You could get a small AC charger to keep the batteries full charged.
   
3. ) You could get a smaller Solar Panel to charge the batteries in one-two weeks, a 25 watts solar panel will do
   
   

You could get a small 200 watts gasoline generator for that purpose as well ( I do have one for that purpose with my "picnic" battery)+ #1, +#2

Regards

nNando

[ghurd]

Yes, Mr. Murphy always shows up sooner or later.

I personally think that SOB is out to get me.

Forgetting about self discharge, higher amps at lower battery V, better power retention with PMW, etc...

The trailer is for storage and lighting it should be neglectible, say 5AH.

The 5 lights for 4 hours with 11W Solsums for example, plus 10% = 20AH/Day.

A 105AH battery should last 5 days without charging.

A 32W panel like the US32 has a amp output of 1.96A x 5 hours per day.

Boy Scouts don't camp out much when it is cold (ie: low solar insolation),

probably because of the leaders / fathers, so 5 hours seems reasonable.

That is 10AH/day charging.

With 8 days of use at 20AH/day = 160AH.

With 8 days of charging at 10AH/day = 80AH.

With 5AH total trailer lighting use,

and a 105AH battery.

That still leaves the battery about 20% charged.

A good, full charged 105AH battery and 32W PV should be good for 10 days before the power runs out.

With a 32W PV and 3 days use per trip, the battery should stay above 70% SOC.

For the Boy Scouts, it is $250 or $650. The $250 system will work fine, IMHO.

I bet the $650 system will not be purchased.

A particularly nasty weekend will give the boys lots of time to try Norm's $25 bike/treadmill battery charger.

What is wrong with my figuring?

G-