1. BATTERIES of Renewable energy systems By Jess, Michael & Emily If one was to perceive a renewable energy system as a living organism, the "battery" would be the "heart" of the RE organism. – Mayflower Trading Company

2. Cells… Most batteries have a number of cells a car battery is 12 volts, and is supplied as one unit (monoblock) standalone power systems -battery banks are supplied as: 12V, 24V, 48V or 120V -batteries can be supplied as a monoblock (12V or 6V) but are generally supplied as individual 2V cells. -A 12V battery bank will consist of 6 x 2V cells etc.

3. 2 main types Lead-acid batteries = most common in renewable energy systems - The electrolyte is Sulfuric Acid - Positive and Negative lead plates Nickel-cadmium = less common, last longer and are much more expensive

4. Advice Increasing the size of a PV array is simple; adding more batteries later is entirely different. - The voltage response of any battery has a direct relationship to its age. - adding more batteries to a system later will only allow the system to perform as well as its worst cell The “weakest link” in any “alternative energy” system is the inadequate sizing of the battery bank design. In the case of the battery, “bigger is always better”. In all cases, use only true "deep-cycle" batteries. (Mayflower Trading Company)

5. Lead-Acid Type Shallow vs. Deep Cycle –S–Shallow cycle batteries discharge 10%-15% of capacity –D–Deep cycle batteries discharge up to 50% of capacity Flooded –“–“Wet Battery” –M–More maintenance intensive –L–Less expensive Valve regulated –C–Completely contained gel electrolyte –M–Maintenance free!

6. Installation Ventilation –P–Produces H 2 and O 2 Out of sunlight Off of cold ground Catch spilled fluid in drip tray Must be clear of electronics or potential sparks

7. Other Notes Batteries are less than perfect containers for storing the energy of our power systems. For every 1.0 amp- hour you remove from the batteries, it is necessary to pump about 1.25 amp-hours back in, to bring the battery back to the same state of charge. This figure varies with temperature, battery type, and age, but is a good rule of thumb by which to calculate approximate battery efficiency. The performance you will get from your batteries will vary with location, climate, and usage patterns.

8. Battery Life and Performance 15-20 years Temperature affected Depth of Discharge affects lifespan Usage affects life span –Constant small load vs. instantaneous large load

9. Typical Cost Good quality 12V battery banks will cost from $1000 to $3000. A 24V bank will cost from $2000 to $6000. More money = more capacity.

10. Suppliers/More Information DEKA –http://www.mrsolar.com/pdf/deka/epm0946.pdfhttp://www.mrsolar.com/pdf/deka/epm0946.pdf Real Goods, Batteries: Questions and Answers –http://www.solareco.com/articles/article.cfm?id=44http://www.solareco.com/articles/article.cfm?id=44 Global Sustainable Energy Solutions Battery reference page –http://www.greenhouse.gov.au/yourhome/technical/pdf/fs410. pdf