Searching for Solar Chargers

Yep. Any supplier of hobby solar cells, either over-the-counter or on-line, will be able to help.

thanks for that. i'm trying to attach a solar charger to a 12v cell, but a 12v, 24W cell is too large in appearance. I want to put a dc to dc converter between the solar cell and the battery if that makes sense!!

The output from the solar charger has to be of greater voltage than the instantaneous voltage at the battery terminals, otherwise charging will not take place. It is commonplace to insert a rectifier in the connection so that the battery will not damage the charger if the battery voltage is the higher one. The expression "24W" cell conveys little meaning, unless it denotes a type of cell, such as "PP3" or "AA", which determines the international shape and connections.

Any battery will only charge at a rate determined by the current that is fed into it, and in the case of a solar charger, that current is determined by the strength and to a certain extent the colour of the light that is falling on it. To obtain more current, one merely adds solar cells to obtain the required illuminated area, electrically connected "in parallel", or increases the strength of the light in some way: lenses or mirrors might do the trick, though it is easy to cook anything by concentrating the sunlight falling upon it.

puchase? yes, of course.

make? why not? what better way to sharpen your brain than by making this thing yourself?

check out these instructional links:

http://www.youtube.com/watch?v=YuzU8UBTs3c

http://www.dxzone.com/dx18805/diy--solar-powered-battery-rechargers.html

http://www.popsci.com/diy/article/2007-07/diy-solar-charger

http://www.survival-homestead.com/diy-solar-battery-charger.html

i just happened to find some Super cells. each one outputs 0.5v, 60mA. i think i can link these in series and run them through a dc to dc converter to double the output. regulate the current and i think i have myself a winner!!!!

you'll have to excuse my lack of knowledge, i am currently studying electrical installations so am relatively inexperienced!!

The phrase "double the output" worries me. You can double the voltage, but you cannot double the power. If you take a dozen of your .5v, 60 ma cells and string them in series, you will have 6 volts at 60 ma. In a perfect world, going through a boost dc-dc converter, you could get 12 volts at 30 ma... but the world is not perfect. If your converter is 80% efficient, you would get 12 volts at 24 ma. To charge a 12 volt battery, you should actually put out about 13 volts, so using 80% efficiency, you would get 22 ma out. For lead-acid batteries, I use 13.8 volts. It depends alot on what type of battery you are charging.

Since you are space constrained you might want to consider arranging your cells like a bee hive. One cell in the center, with 6 around the center cell, then additional cells around each of the outer 6. This configuration gives you the maximum number of cells for a minimum surface area. Stuff as many cells as you can into your surface area and series connect them. Idea is to get maximum power into your DC-DC converter, and get you maximum current out at 12 volts... 13.8 volts... whatever.

Bill

Yes they can be purchased at most hardware stores here in the Southern U.S. Many game feeders use 6V motor and battery. Solar chargers are used on these to keep the batteries charged year round ( many hunters feed year round and then ambush deer during deer season). By stringing enough of these 6V panels in parallel, you could get the 2 amps necessary to achieve 12 Watts. Intensity, and as previoulsy stated colour, will play significant roles in the number of parallel cells needed. The good thing is that it should last a long time. A decrease in I (current) is easily fixed by decoupling the cells, then test and replace the single defective panel.

Look at REUK.co.uk. They do both