Making a Solar Powered Generator?

Question

I know basically next to nothing about electronics, as im sure this is a fairly easy thing to construct if I had the faintest idea.

I know I need a solar panel (duh)

I know I need a power inverter to make the current ac

I know the batteries i need need to be deep cycle batteries.....is it possible to link these together? So that once one battery was full the solar panel would keep on filling the adjacent batteries? Is there a limit on how many batteries?

Also I have no idea how i would wire any of this up......

I know this is a very big question to answer, but any help is appreciated

Thanks

Answer 1

Check  www.instructables.com

There you will find TONS of plans and projects on DIY - Do It Yourself building.  Type  "solar powered generator" in the search. I found about a dozen projects related to your question.

There is a small circuit that will control the charge to your batteries, and if you wire them in parallel you can have many batteries and keep the same voltage (12 volt for deep cell marine batteries)

You need to add up the draw in amperage to see how big of an inverter you will need to run your devices.

Answer 2

The first question to ask is how much power will be required. Sunlight has an average of 2 watts per cubic centemeter. Solar cells are only 10% efficient, so the cells will only generate 200 milliwatts per cubic centemeter. Roughly speaking, a pair of solar cells capable of running the average toaster would be about 2 by 4 feet.

Of course, this is why batteries are always a part of a solar array because it is easier to store electrical power and use it later. Batteries can either be connected in series or parallel. A series conncetion links the negative terminal of one battery to the positive terminal of the other. It is like a group of elephants marching along holding each other's tail. The circuit is tapped by holding the trunk of the lead elephant and the tail of the last elephant. This circuit maximizes voltage. The other connection is a parallel connection. All the elephants hold trunks and their tails are tied together. This circuit is tapped by holding any elephant's trunk and any elephant's tail. Electrical engineers refer to the terminals as "rails". The DC circuit will have a positive rail and a negative rail.

Next comes something loosely referred to as an inverter circuit. It changes the DC output from the batteries to 60 hertz AC current needed by most appliances. The AC output voltage is also fixed around 120 volts. Because of this, a parallel battery circuit might be the best choice of an input to the AC/DC inverter/converter.  A parallel circuit has a voltage fixed at the maximum output of any single battery on the rail; the advantage is this circuit stores lots of current. It's like pouring water out of a bucket connected to 10 other buckets. The bucket won't drain until one has the equivalent of 10 bucket's worth of water.

Therefore the trick is going to be finding an inverter which will produce 120 volt AC around 60 hertz. Just such a circuit is available in automotive shops. These are the sorts of things which allow campers to run AC appliances off their car battery. Inverters are very easy to get and also cheap. They are designed to run off a 12 volt source (current is not an issue here). Depending on your power requirements, 12 volt car batteries can be used, or smaller motorcycle batteries if space and weight are conciderations. Remember, the input voltage is going to have to be 12 V DC.

The major cost of this system is going to be the solar pannels. Solar technology is still rather crude and uncommon (READ: inefficient and expensive). Some distributors manufacture blanket style cells which lay on top of a a dashboard and charge a car battery. These would be perfect to use with an automotive inverter circuit. Just hook the solar pannel to the battery and the battery to the inverter. Sunlight will go in one end and AC current will emerge from the other. A DC voltmeter is going to be very helpful in determining the polarity of the DC hookup. This is going to be between the output of the solar cells and the input and output to/from the battery (batteries) and the input to the inverter. In fact the whole section up to this point is going to be a parallel connection. The positive terminal from the solar cell(s) will run directly to the positive terminal on the batteries and then on to the positive input terminal on the inverter. This is going to be the positive rail. All positive terminals of solar cells and batteries will be connected directly to this rail. The rail will then run to the positive input terminal of the inverter. Likewise, the negative rail will be connected exactly the same for all the negative terminals.

This is going to look somewhat like a ladder design, each rail will be opposetly charged (positive or negative) and all solar cells and batteries will be connected like the rungs on the ladder. The important thing is to get the polarity right. If the negative terminal of a barrety or solar cell is accidently connected to the positive rail, a short circuit will result. Depending on the power generated, it can be anything from a nusciance to a disaster.  Always remember, electrical engineering is very much like chemistry - each is not something to get involved with if one does not know what they are doing!

Finally, I'm sure there are a number of formulas available which will allow one to calculate things such as how much power can be generated, how long the batteries will need to be charged and how long AC power can be tapped. If this circuit is hooked up correctly and works successfully, perhaps just taking notes on the preformance might be more entertaining - and accurate as well. Most scientific formulas are based on incredibly simple situations. As more elements are added to a design, the less reliable an approach based on pure calculations becomes.

Hope this helps. have fun and remember to be careful!