There's an interesting "back story" to the 1996 battery study you cite, Joel. It illustrates the pitfalls that can occur when you don't ask the right questions of the right people.
I reviewed that study a few years later, and was surprised to read that Mr. Hund's survey suggested that 64% of batteries used in PV systems were VRLA. >From that study: "Table 1 presents a preview from the battery survey listing total flooded and VRLA battery sales from the 21 PV system integrators for 1995. The data indicates that 64% of the PV batteries sold are VRLA with a dollar value of $3.4 million." My own observation suggested that this number was way off: I knew of virtually no one who used sealed batteries for typical residential off-grid homes. I had the opportunity to question Mr. Hund about this at some technical forum. When he explained that this number came from a survey of RE wholesalers' battery sales, it all made sense. Sealed batteries can be shipped; flooded batteries are generally delivered by trucks operated by battery wholesalers. If you only ask RE distributors what they sell, the answer will reflect this reality. Mr. Hund asked the wrong people, and drew an erroneous conclusion from the answers he received. A year or two later I was talking with someone in tech support at Morningstar; I think it was about how easy it was to default the charge voltage setting on an early ProStar controller to the VRLA setting. If you ever disconnected battery DC to the controller, it repowered up at the lower VRLA voltage, and must be reset each time to the higher settings needed for flooded batteries. The technician defended the structure by referring to a Sandia study that found that nearly 2/3 of batteries in PV systems were VRLA. When I explained the fundamental flaw in the study that led to that conclusion, the Morningstar technician was pretty surprised. A year or two later, the second-generation ProStar was released, that is still in current production, with a rotary switch setting that is set once and returns to the same setting - gel, VRLA, or flooded - when powered up. I have long remembered this as a good lesson in how poorly crafted research can result in unintended consequences. Allan Sindelar al...@positiveenergysolar.com NABCEP Certified Photovoltaic Installer EE98J Journeyman Electrician Positive Energy, Inc. 3201 Calle Marie Santa Fe, New Mexico 87507 505 424-1112 www.PositiveEnergySolar.com -----Original Message----- Here's some good info: http://photovoltaics.sandia.gov/docs/battery1.htm or http://www.osti.gov/bridge/purl.cover.jsp;jsessionid=CC366D87BBE1C7C3BCBEEAF D87A3D0D7?purl=/402426-htwdT8/webviewable/ or http://www.osti.gov/bridge/purl.cover.jsp?purl=/125071-E7W1qQ/webviewable/ Joel Davidson _______________________________________________ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Options & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org
