RV Solar Power Paper December 25, 2011, 04:38:40 pm Yahoo Message Number: 127494On this Christmas afternoon, the kids are gone, the house is quiet, so I uploaded an article on Solar Power to The Companion. http://lazydazearticles.blogspot.com/Before running off to read it, you should know the author said "Being very much a citizen of Nerdvainia I often don't have a good feel for 1) the level to present stuff for a general audience and 2) whether I am answering the questions people have" OK, that's fair. I think it's technical and over the heads of a lot of us. However, that's no reason to withhold publishing it. I know there are folks here that will understand it. To those who don't, ask questions and Linley may well write a second version.My thanks to Linley in the snowy NW.
Re: RV Solar Power Paper Reply #1 – December 26, 2011, 09:38:19 am Yahoo Message Number: 127498QuoteOn this Christmas afternoon, the kids are gone, the house is quiet, so I uploaded an article on Solar Power to The Companion. http://lazydazearticles.blogspot.com/ Don, not clear if this is your article or not, but although it is a pretty good description of direct relevance to LD owners, I would like to make one point related to solar charge controllers. The author separates them into 2 classes, switchmode and MPPT. However, within the switchmode, he is actually referring to two entirely different animals - an issue a LD owner purchasing their system from the factory may not have to deal with. All LD historically came from the factory with Heliotrope models which were either true switchmode or MPPT units. However, most inexpensive packages purchased elsewhere will tend to include a very basic switching controller which is not actually 'switchmode'. These basic models are usually 'shunt' controllers, and while they do switch on and off to control the charge flow, they do it differently. Typically, they charge up to about 14.2V while on, then turn off until the voltage falls to about 13.2V, then switch back on. As the system we installed about 17 yrs ago included such a controller, I am very aware of the shortcomings of those. Here is the problem: when the controller switches off at 14.2V, the battery is far from fully charged. The surface charge on it will quickly dissipate, dropping the voltage back to 13.2V. The controller then switches back on, the voltage rises quickly to 14.2V, and it's off again. The closer to full charge the battery gets, the more rapid this cycle, but the battery will accept several amps at 14.2V, and practically nothing at 13.2V. As a result, the average current is far less than a switchmode controller, which maintains the voltage at 14.2V while monitoring charge current. Quite simply, within the period of a normal solar cycle (1 day) the shunt-mode controller may never bring the batteries to full charge. When I replaced my old controller a few years ago with a more modern model, either a switchmode or MPPT model would have been adequate. However, the price difference was marginal, so in those circumstances, choosing an MPPT model was the way to go. The choice for someone whose current controller is a good switchmode model is not so clear, however. An MPPT model only has the advantage for a few hours of somewhat higher charge current for well depleted batteries, or for circumstances which also include heavy power consumption while the solar system is active. Many folks would never notice any difference with an upgrade.Steve
Re: RV Solar Power Paper Reply #2 – December 26, 2011, 09:52:16 am Yahoo Message Number: 127500On Mon, 26 Dec 2011 15:38:15 -0000, "aq433" aq433@...> wrote:QuoteDon, not clear if this is your article or not Since it has Linley's name on it, it's is 100% his.
Re: RV Solar Power Paper Reply #3 – December 28, 2011, 04:27:25 pm Yahoo Message Number: 127535On Sun, 25 Dec 2011, Don Malpas wrote:QuoteOn this Christmas afternoon, the kids are gone, the house is quiet, so I uploaded an article on Solar Power to The Companion. http://lazydazearticles.blogspot.com/ Nice job, Linley of explaining a relatively complex subject in a very easy to understand way. I might just add that anyone looking at the "charge voltage vs temperature" table can really appreciate the need for a temperature compenstaion probe for any battery mounted in an outside compartment. There is over a 10 percent change in values over the 20 to 100 degree temperatures in the table.QuoteMy thanks to Linley in the snowy NW. My thanks too, but the Pacific NW is anything but snowy (Mountains excepted of course) Temp today is low 50's.Rich Gort - 2000 MB - Birch Bay, WAHappy and Healthy 2012 to all
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