Pizza topper light?

[Frankenamp]

 Hi Guys:
I'm trying to make some points with the better half-
This involves making a solar powered light for her pizza-topper sign on her car.

I'm thinking one with a strip of solar cells along the top to a charger & battery pack hidden inside with a little mini switch to turn the led's on & off. the one she has already has a little plug and lights inside to hook it up to a cigarette lighter... but I want to set her up with something a bit more "elegant".  Kinda like those solar 'Malibu*' garden lights (that never work right) that actually works!

Is there something you guys have seen that can be easily adapted to do this?
Thanks in advance

Frank

[EL34]

The problem I always see with solar charging is that the charge rate is very low compared to the discharge rate of LED's that are bright enough to be seen.

[Frankenamp]

Yeah, I've noticed that. That's why I have been thinking about cobbeling up something from misc parts. None of the solar path lights ever give much light or last very long. I'm almost tempted to figger a way to put a little wind tunnel thru the center of the pizza topper with a little wind generator! Not sure the wife will appreciate the reasoning... I figure with a 4 0r 5 volt battery pack and at least a couple of panels paralleled to trickle charge (and a daylight sensor)  I might have something feasable...

[EL34]

Those LED's I use for bike lights discharge at 2.8 amps
The battery packs are 3.6 volt Li-On cells in parallel.
The chargers charge at a 1amp rate and still take many hours to refill the packs.

[PRR]

The capital investment in solarcells and storage battery is FAR larger than the cost of a cigar plug to use the existing ample generation and storage (car alternator and battery).

I doubt it would pay-back in this decade.

I'm sure it is uneconomic for self-funded pizza delivery.

Yes, you are burning drops of gasoline instead of afternoon sun. But making those panels and batteries requires energy, probably Chinese coal; and silicon fabrication is notorious for toxic wastes (one reason the racket keeps moving, from the Bay to Arizona to El Salvador to Philipines to Singapore to China... one step ahead/behind pollution hassles).

Use the LEDs, if you can find enough BRIGHT ones to do the job well. But in a car, solar does not IMHO make sense until you can DRIVE the car with solar. (Which will mean far smaller cars driving far fewer miles.... give up this silly idea that someone should drive 10 miles and back for a pizza.)

[Frankenamp]

I try to drive less than 10 miles for my pizzas The landlord has a pizza shop a bout a half mile away (best pizza in Fremont- not just my opinion) second best is a take & bake joint (poppa smurfy's) about 2 miles; Papa John's- (best pizza in Vegas) has a franchise about 5 miles away owned by an east indian, which normally wouldn't be a bad thing, but the last time I darkened their doors, the owner was telling the tatooed hired help that he'd better get with the program and learn his stuff so the owner could take a vacation in India (those are traditionally at least a month) I thought it was bad form to be dressing down the hired help in front of customers and the lack of tact was annoying as well...

However, the pizza topper no longer has the logo of a pizza establishment on it. It is currently advertising both far and wide that my wife has an unlimited supply of fine AVON products to sell... (it thrills me to no end that she now has her own car) My gratitude is such that I was willing to indulge her desire to have a solar light for her pizza topper. Plus driving down the hiways and byways with a wire through the window flapping in the breeze is less than desirable. The light dosen't have to be very bright, just enough to make the topper visable to the other traffic, and parked cars.

[EL34]

If you don't want to use a wire and you have room for a Li-On battery pack inside, you can light up the insides with LED's and charge the battery pack at home

[PRR]

> indulge her desire to have a solar light for her pizza topper

Ah. Well, since it isn't impossible, and not grossly expensive, you HAVE to do it.

> you can

No. It's her car. She could, but won't.

> a Li-On battery pack

The key feature of Li-On is small weight and size. Perhaps not worth the cost here.

I'd go crude. Lead-acid sealed gel-cell security alarm battery (Home Depot has em). Lead batts can be charged recklessly.

There's a solar panel for trickling RV batteries at WalMart etc.

Doug has your LEDs. Pick a number of LEDs to give good light all around, and also come up to a little under 12V.

Estimate how many hours of topper-light a day.

Figure amp-hours and over-size your battery (for some reserve on cloudy days).

Read the solar panel specs, discount for real-world conditions, figure your hours of good sun there, and buy a panel which will fill-up the battery in less than one day (reserve for cloudy afternoons).

Figure how you are going to mount the large solar panel. There's teeny ones which won't do the job, 42" panels which will over-do the job but may lift the car at 70MPH.

Get an artist to draw a big "Solar AVON!" logo. If you are going to this much trouble and expense, she may as well get some business advantage out of it. No matter that a solar light adds nothing to the value of the AVON products.

[Frankenamp]

That's what I'm talkin' bout! The topper does have a jack that I can use to plug in the solar thingie. I've seen several kinds- I'm hoping that there's one that has a magnetic back ( or that I can schlep a few pieces of magnetic tape on) so I can stick it on top of the car to charge the alarm battery with. Do I need a 12V battery, or can I cheap out with a 6V battery (or will the solar charger overcharge it?) I'm thinking most chinee solar cell chargers will only put out a few milliamps... now, off to cruise Doug's Diode Emporium...

EDIT:  From Ms. PizzaTopperOwner- "You guys are bein' FAR TOO COMPLICATED! All I wanna do is find out a way to stick some solar cells on top of my topper to charge some LED Batteries"  She got some LED Christmas lights last year from Australia that charge pretty good and last reasonably well and is convinced that's what she needs (or a reasonable semblance) She's about ready to stuff the whole string of lights in the topper and schmeckle the solar unit to the top of the topper...

[PRR]

> can I cheap out with a 6V

Batteries go by the pound, very nearly. 12V 5AH is just a tad more than 6V 10A.

You "cheap" by buying a battery which fades before the trip(s) is over.

Also: Doug gets good results with one LED on 3.6V battery, direct for Bright or with resistor for half-bright. 6V is too much for one, not enough for two. Three such LEDs will work with 10.8V, which is near-enough to 12.6V-11.5V that you don't have big waste.

I'm thinking.... Doug says one Bright LED blinds oncoming cars, though perhaps because it is so small (far smaller than a car headlight). When you spread it out over the letters A-V-O-N it may be kinda dim for attention-getting. Three LEDs will light one side pretty good. You want it to shine coming and going. Two strings of three LEDs.

Max current is 2.8A, half-bright is something like 1.5A. Two strings is 5.6A or 3A.

How long must it run? 1 hour, a 12V 6AH batt will go dim and wear out in a year. Unless it turns out the half-bright is fine, then 12V 6AH is fine, up to an hour. If she's driving 4 hours on Bright then we are up at 23AH which is half a car battery.

Northern Tools has a car-charger 12"x15" rated 11W for $79. Assuming 13V charge that means 0.8 Amps in full sun at optimum angle. I don't even know where you are; south end of the Bay or out in Vegas? In Maine it gets dark in winter. Say 6 hours sun, 5AH, times 0.7 for being flat rather than aimed at the sun, 3.5AH. Hmmm. This says two $80 panels to run 1 hour at half-bright. Four hours at full 5A current needs SIX $80 panels.

Amazon shows a 15W 12V 16"x42"(!) for $92. Similar on eBay selling at $55. Forget battery cost, solar panel costs will dominate the overall cost.

You could scale WAY down on brightness. I have a solar house-number light. In NJ it was just barely brighter than sky-glow. Here in the dark woods I can see it many hours after sunset. I don't think it would get noticed on a highway full of headlights. But heck, it was cheap, list $50 but generally found for $20. Cut AVON out of black plastic and glue over the number area, show her.

[EL34]

I think the SSC P7 LED we use for bike lights is way too bright, uses too much current, needs a big ass heat sink and is too expensive for this project.

I would probably solder a couple strips of super bright LED's in series and use some sort of common and cheap battery like PRR has mentioned.

I have used these LED's for a couple projects with good success
Cheap at 25 for $2.60 and free shipping.
http://www.dealextreme.com/details.dx/sku.1106

Here's 8 of them on my CNC machine
I run them at 25 to 30ma each
Project page - http://www.el34world.com/Misc/Cnc/CNC8.htm

[billcreller]

I thought about some lights like that for emergency lighting in my house, that don't use a lot of power, like in stairways etc. I know nothing about what's required for power etc, so I would have get educated on that.
 

[simonallaway]

We have wind farms around here with literally hundreds of miles of wind generators you can see at night, all blinking at the same time, not sequentially or random.
If it were not profitable, they wouldn't be doing it.

I'm all for renewable energy, but I'd like to see it perform profitably without government subsidy.