Dear Jeff,
Having recently bought some land in Missouri that is located out the the sticks and very much at the end of the power grid. I have pretty well deduced that I will need some back up power.
Recently I have discovered the backwoodshome.com website and a number of your articles. As one who is not totally familiar with alternative power like wind and solar, everything I read seems only to confuse me more.
With interest I have read about l-16 industrial batteries for a battery bank in some articles. In an article about adding a solar cell to a truck camper a RV/marine battery is recommended. Since RV/marine batteries are easy to find and will take to repeated charging wouldn’t they be logical choice for a battery bank vice the harder to find L-16?
I have noticed too that with wind power most often suggested is a dc wind generator that requires upwards of 6 or 7 knots of wind to operate. In searching around I have found a source for a AC wind generator that begins operation in the sub 7knot range. AC generators have to best of my knowledge a big advantage over DC generators and that is in size of the cable between the transmission line from the tower to the battery bank. An ac generator can use a standard ac power cord and suffers no loss in current between the tower and batteries.
I have to admit that my understanding of the way a ac generator works is taken from the following website: http://www.tlgwindpower.com/default.htm On the opening page there is a photo of a customer using 9 ac wind generators on his farm in Wisconsin. Although wind power as such is confusing to me I believe that this ac system must be quite good or the farmer who had added to it and bought these generators would not be doing so if they weren’t efficient.
Perhaps you can give some insight into battery banks and DC versus AC generators in a future story. Also the battery bank issue of l-16 versus marine batteries is very confusing to a novice seeking information like myself.
Any information you can provide along these lines would be greatly appreciated.
Thank You
Keith McElroy
Keith:
Lots of questions! Actually you are talking about “L-16″ batteries, not “I-16″. When I suggest using an RV/Marine battery, you will find that it is for a small 12-volt DC system that does not have a large load that would fully discharge it each day. These batteries are much heavier duty than a typical car battery, and most have re-combiner caps and do not need to add water. However, they will NOT hold up to a daily deep charge/discharge cycling like a solar powered home or cabin. For these larger loads and system sizes, the lowest cost battery designed for a heavy charge/discharge cycling each day is a 6-volt golf cart battery ( T-105 size). These are less than $100, and can be found at most big box stores during the summer months. They are about the same size as a car battery, but because they are 6-volt, the plates are very thick and very heavy.
For a 12-volt system you will need two 6-volt batteries wired in series, and for larger systems you will need 4, 8, or 12. When you start getting above 8 batteries of any size, its better to switch to a larger amp-hr battery and stay less than 16, as this can cause problems with un-even charging and dis-charging when you have multiple strings of parallel batteries.
I think you are caught up in the AC or DC debate as a marketing ploy. There is no engineering difference in the amount of wind it takes to turn a wind turbine based on AC or DC output voltage. Wind energy is a “cubic” function of the area of the blades, and below around 7 MPH I think you will find most small-scale generators will not provide any real power, although the blades might turn. There are now both AC and DC wind turbines and each has its advantages, but only in wiring and additional equipment that will be required.
A 24 or 48 volt DC output wind turbine is very easy to add to an existing solar-power system, and some models have built-in charge controllers and can be hooked directly to the batteries. Yes, this will require a larger wire size since the voltage is lower, but the ease of wiring is its real advantage. Also, unless you are talking about some huge wind machine on a 150-foot tower, the difference in wire costs would most likely be less than 50 cents per foot for the larger wire caused by using a lower voltage DC model. An AC wind turbine can use a smaller wire size since the voltage is higher, and these are usually designed for grid-connect systems without batteries. There are a few other issues, but you cannot say an AC unit works better than a DC unit having the same size and blade design, and the reverse is also true.
Good luck!
Jeff Yago
