On Thu, Aug 12, 2010 at 11:25 AM, Aaron Toponce <aaron.topo...@gmail.com> wrote: > On Thu, Aug 12, 2010 at 10:38:18AM -0600, Michael Torrie wrote: >> >> Regular UPS units use normal, sealed leadacid batteries. Anyway, going >> solar is a neat idea. Let us know how it works out and how the >> economics fly. Are you planning, then, an off-grid system? > > I thought they were "gel cells", but looking at Wikipedia, I guess > they're essentially the same, except the cell chemical is different, and > the lack of needing to add water. I don't know about the power draw > differences between the two, though.
There's a wide variety of lead acid batteries. There are two basic categories, starting and deep cycle. There's also a sort of hybrid between them. Starting batteries are optimized for delivering high current for short periods of time, while deep cycle are optimized for delivering lower amounts of current for longer periods of time. Starting batteries are not very good for reserve power applications, since they can't be discharged very far before they start to be damaged. If you put a bunch of car starting batteries in your system, you'll be replacing them before too long, especially if they were used to begin with. There are also different types of electrolyte. Auto batteries are typically an open wet cell battery, which has serviceable electrolyte and vents hydrogen gas when it changes. There are also deep cycle batteries of this variety, and they're relatively inexpensive, but you have to be careful with maintenance and storage to ensure the gas doesn't corrode the terminals and that there's enough air circulation to vent the hydrogen so it doesn't build up to dangerous levels. There are also sealed varieties, such as gel cells and AGM. These don't typically vent, they don't have serviceable electrolyte, and they don't spill so they can be installed in different orientations. Gel cells can be ruined by charging them with too high of a voltage, but AGM don't typically have that problem. AGM are the most common type of sealed battery now, I believe. I've got one as a starter battery in the trunk of my Miata, and I've got a small deep-cycle one as the house battery in my Vanagon Camper. > > It'll be hybrid. Eventually, I would like to go 100% off-grid, but that > might be a bit. Looking at 220W panels for roughly $500 makes it very > attractable for my wife and I. > > > Not only solar, but I've looked at a gas generator as well. Gas is > cheap, and the generators are inexpensive, so that could work in an > emergency for a day or two worth of power (as long as I can keep feeding > it gas). There's more to the system than just the panels, of course. You'll need to factor in the correct batteries for your needs (different kinds of batteries have different points at which further discharge starts to cause damage, so you have to factor this into capacity calculations), a charge controller to make sure that the batteries are charged and discharged properly, a properly-sized full sine wave inverter to run your AC appliances, and whatever other gadgets that are necessary to integrate your system with the grid and gas generator. Presumably you don't want to go shuffling plugs at your breaker panel whenever you want to switch power sources, and hooking things up the wrong way can backfeed power where it shouldn't go and cause serious problems. You could blow up your own equipment or electrocute a utility worker if you hooked things up wrong. The above equipment is generally not cheap. :) As far as solar goes, you might also want to consider solar water heating, which could also reduce your gas bill. It doesn't involve expensive photovoltaic cells, so it could be cheaper to implement. --Levi /* PLUG: http://plug.org, #utah on irc.freenode.net Unsubscribe: http://plug.org/mailman/options/plug Don't fear the penguin. */