by WisJim » Tue 20 May 2008, 13:51:16
I have been using lead acid batteries in a wind generator/PV system since the mid-1970s. I started out with used telephone company batteries that were about 10 years old, then got a second and third set of similar age. When we moved after using them for 12 years or more, they were still usable, but showing their age, so we took them to a salvage yard and got many times what we had paid for them. After we moved and reinstalled our wind/PV system, we used another set of used telephone batteries before buying a set of brand new forklift style batteries. The last set of telephone company batteries that I had were over 25 years old when we quit using them, and my new batteries are about 10 years old now, and still look and act new. I expect them to last another 10 or 15 years with the kind of care that I give them--never let the electrolyte get low, and never let them discharge below 80& of a full charge for long. I do have the option of using grid power to recharge if it is calm and cloudy for a long time, now, but we can easily live with the amount of power that we generate, even with charging the Comutacar, lawnmower, and electric bicycle batteries from the system most of the time.
Someone inexperienced in taking care of batteries might only get a few years from an inexpensive set, but after learning what to do and not do, and actually doing it, you can then buy a set of really good batteries that will last for decades.
I have had friends use Edison (nickel iron) batteries with their off-grid systems, but I think that all of them have since gone with lead acid batteries. The Edisons have a long life, but they require a much higher voltage than their nominal voltage to be fully charged, and it can cause problems with the rest of the electrical system. They also have a high internal resistance which can limit the maximum current drawn from them without overheating and damaging them. Old Edison cells are sometimes available that might be 30 to 50 years old and still usable, after cleaning and changing the electrolyte. They are also not as efficient as lead acid batteries in their charge/discharge cycle.