Banks of Batteries
Storing the electrical energy that has been converted by your source is the hardest part of the home-energy process.  Most systems use lead-acid batteries, which can not be constructed very easily in your average home workshop.  Still, they are efficient compared to the cost, and along with conservative energy use, deep cycle batteries can play a very important role. Lead-Acid battery systems can be any voltage, but most people use either 12 or 24 volts.

So, what is a battery?  A battery converts the electrical energy from your generator or solar panel into chemical energy by means of a specific chemical reaction.  When you need to use electricity, the battery reverses the chemical reaction and releases electricity.  Batteries come in all shapes and sizes, but for most small home systems, deep cycle lead acid batteries are used.  These batteries can be found in most cities, and have many applications including golf-carts, forklifts, and telephone lines.  Lead-Acid Batteries are rated in Amp-Hours, which means they contain a certain amount of time at a particular electrical draw.  A 200 amp-hour battery with a 20 amp draw will be discharged in 10 hours of use.  So, if you had a lamp that pulled 2 amps, you could light a room for 100 hours.

Most batteries in this class come in 6 volt sizes, but most appliances are at least 12 volt.  To get around this, we use two 6 volt batteries, wired in series, to get one 12 volt battery.  Then, our 12 volt batteries are wired in parallel to give us more amp hours. 

Because batteries are expensive, you will want to make them last as long as possible. Checking the water level regularly is vital, and should be part of your general maintenance schedule. Another key factor in the lifespan of your batteries is not leaving them drained too low for too long. We have learned the hard way, and it has cost us dearly. Now, we try not to drain our system below 12.0 volts (a battery is full at 12.6 volts), and so far we have been very pleased with the performance of our battery bank.

One thing to note, when reading the level of your batteries, is that you will only get a true voltage reading when there is no power coming in. For example, if there is no wind or sun, and hasn’t been for a while, your voltage reading will tell you exactly what your batteries are sitting at, 12.6 volts being the maximum. However, when the wind is blowing, your voltmeter might read anywhere up to 14.6 volts. This is because you are reading an average of what your batteries are sitting at and what is coming in.  The closer the batteries are to full, the less they act as a voltage buffer, and the voltage rises faster.

Additional Resources:

• Fieldlines  and OtherPower - The best home-power resources on the web
• Battery Information 
• Solatron Technologies - A great source for components, especially batteries
• Deep Cycle Battery Information 
• Ultimate Battery FAQ