Judy, Your wizardry and willingness to share in such wizardry is awesome. Thanks :)
David On Wed, Apr 14, 2010 at 8:07 PM, Judith Blumhorst, DC <[email protected] > wrote: > > > Rick, > > What is your goal? To keep your batteries trickle charged on a mooring? > Or to go "off the grid"? For a trickle charge panel, less than 10 watts, > you. > > 1. Trickle charging: > > For a trickle charger, the rule of thumb ishat your panel should provide > about 1 watt or less for every 25 amphours of battery capacity. If your > panel provides more than that, you'll damage your batteries. For a 90aH > battery, a 5 watt panel is close enough and you won't hurt the battery. If > you have AGM batteries, which have lower internal resistance and a > negligible rate of self-discharge, you can use a 2 watt panel to keep your > batteries topped up. > > For a two battery bank, a nice system would be a Unisolar flexible 11 watt > panel and a dual battery controller. I like the Flexcharge PV7D. It's a > smart-charger, very effieicent, will charge both batteries, and can handle > up to 7 amps from the panels. It's under $100 at West Marine and can take a > beating or a dunking. That's what I have for my trailer sailboat that > doesn't have shorepower available. (And AGM batteries). > > In sunny San francisco, the 11 watt panel recharges the amps we use on a > weekend daysail (for lights, radio and occassional autopilot use,) as well > as maintains the battery. We don't have or need a cranking battery, just > enough for one light inside and the vhf and the stereo. We rarely sail at > night, and we carry battery powered backup lights for longer trips, just in > case. > > 2. Small solar system for 3 season use "weekender" use, providing moderate > creature comforts: > > The biggest panel manufactured for 12v systems is 135watts. For that you > would need a conroller. A 135w panel is the largest one made for 12 systems, > and they generally can't produce more than approx 7.5 amps per hour under > ideal conditions, no matter what the voltage. So you could use a 7-10 amp > controller with a single 135w panel. You can put together a nice135w > system with controller for under $500. Depending on your weather, that'll > give you up to 50 amphours a day in the summer, 30 in the fall/spring and 15 > amphours in the winter. That's just right for a two bank system of about > with two house batteries of 90-100 aH each. Use one battery for the engine > and use the other two for the house. You'll have one days' reserve capacity > in the house bank if it rains. In the winter, you're not going to get > enough juice to use all your creature comforts, so use shorepower. > > 4. Off the grid livaboard system: > > For an "off the grid" 12v system, to provide more creature comforts, costs > jump geometrically. You'd need a lot more panels, wired panels in parallel, > and a controller with the apropriate amperage range. Now we're talking > around $250-300 and up for a controller. $300 per panel. Mounting systems > for the panels. Wiring costs increase as the diameter of wire increases. > And if you really want to go off the grid, then you need to invest in a much > larger battery bank. So now we're adding more weight and more expense. > > 5. The moral of the story: > > If you can keep your consumption down to 25-30 amphours per day of usage > for spring/summer/fall, you can get away with about $500 for the solar > system, (and $500 for two nice AGM batteries that'll last you 7 or 8 years > and charge up really fast) > > 6. Or get a Honda 2000i gas generator for $1000.... and run it on the > foredeck. Use your fridge and microwave as much as you'd like.... > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > I plan to buy a 135w panel. 135watts/12v = 11.25 amps right? So if I have > my 135w panel out for an hour at noon, I should get 11 amphours worth of > charge in my batteries, right? > > Sorry, but that's not how it works. You'll get about 6 amphours back in > your battery bank in one hour at noontime. > > A 135 watt panel can't produce more than about 7.5 amps. Photovoltaic > panels are nominally rated at 17.7 volts... so that they produce enough > voltage to charge a battery even if conditions aren;t perfect and part of > the panel is in shade .So 17.7v * 7.5a = 135 nominal watts. But at 12.3v > the equation works like this: 12.3 * 7.5 = 92 watts. > > To figure the output of a system, you use the 7.5 amps x the number of peak > sun hours. then de-rate that output by 0.80 (average) for system > ineffieicencies. So you get 6 amps per hour in the noon-day sun. > > (You need between 13.5 -14.3 volts, which is the range that's required to > fully charge a battery. And if the day is too hazy, or the sun angle too > low, or more than about 30% of the panel is shaded, the voltage drops too > low to charge the battery.) > > That's all I can tell you in general. Designing a system gets down into > the particulars. But I hope this helps provide some practical guidelines > for cost vs. benefit. > > Fair winds, > Judy B > > > ------------------------------ > *From:* Sonshingle <[email protected]> > *To:* [email protected] > *Sent:* Wed, April 14, 2010 4:21:03 PM > *Subject:* Re: [IC27A] Re: Solar system [was: Inconvenient battery > installation on Catalina 27] > > > > Judy, > > This is excellent information and thanks for sharing it. What have you > learned about voltage regulation to the batteries? I understand there has to > be some sort of regulator to prevent overcharging and that good regulators > carry a pretty good price tag. > > Dick Schmidt > Greenville, NC > Rush NoMore > > --- On *Wed, 4/14/10, Judith Blumhorst, DC <drju...@blumhorst. com>*wrote: > > > From: Judith Blumhorst, DC <drju...@blumhorst. com> > Subject: [IC27A] Re: Solar system [was: Inconvenient battery installation > on Catalina 27] > To: ic...@yahoogroups. com > Date: Wednesday, April 14, 2010, 5:18 PM > > > Hi Tim (And David) > > I have completed the first two courses for my solar designer > certification with NABCEP, the North American Board of Certified Energy > Practitioners. > > Let's see if I can help a little here.... > > Here's a real-world example, based on my homeport -- sunny San francisco, > at latitude 38 degrees. A high-quality 135w solar panel will replace > about 30 usable amphours per day to my high-quality batteries per day, if I > have a high-efficiency solar charge controller. > > Where are you located? How much sun you get determines how much power > your panels generate. The rating on the solar panel doesn't tell you what > you're going to get in the real world. It's just an output rating in ideal > conditions. (And the definitions aren't always what you'd expect). > > Good panels put out more juice than crummy ones when the sun isn't > perfect. Efficient chargers constantly adjust the "maximum power point" > varying varying the resistance to the panel so they put out the most usable > amps at the right voltage. Good batteries have low internal resistance and > can absorb a charge faster and with less wasted energy. > > With less than excellent components, you might get only half as much usable > amp-hours out of your system. > > And your location makes a huge difference: > To size a solar system for a given geographical location and climate, we > use a concept called "peak sun hours" > > In san Francisco, we get the equivalent of 7.3 peak hours, hitting a > horizontally mounted panel. In January, we get the equivalent of 2.2 peak > hours. For the whole year, we get an average of 4.7 peak hours per day > > And then we have to "de-rate" the performance for factors like temperature, > dust on the collector, electrical resistance, etc. An efficiency factor of > .80-.85 would be excellent performance in the real world. .75 would be > average. > > Here are some good links to play around with... > > For peak sun hour factors by city and state in the US: > http://rredc. nrel.gov/ solar/old_ data/nsrdb/ redbook/sum2/ > state.html<http://rredc.nrel.gov/solar/old_data/nsrdb/redbook/sum2/state.html> > > For a solar system sizer (for off-the-grid systems) > http://www.advancepower.net/advcalc.htm > > Fair winds, > Judy B, > ------------------------------ > *From:* Tim Millar <seascoutship76@ verizon.net> > *To:* ic...@yahoogroups. com > *Sent:* Tue, April 13, 2010 1:20:19 PM > *Subject:* Re: [IC27A] Inconvenient battery installation on Catalina 27 > > > David, > > Got my answer from Coleman/Stearns Consumer Service: > > The Coleman Solar Charging units are licensed products manufactured and > distributed by ICP Solar Technologies, 7075 Place Robert Joncas, Suite > 131, Saint Laurent, Quebec H4M 2Z2, Phone: 888-427-7652 or 514-270-5770 Ext. > 133, info-customers@ icpsolar. > com<http://us.mc450.mail.yahoo.com/mc/[email protected]> > , http://www.icpsolar .com. That's one possibility - double battery, > controller = about $140. > <http://www.icpsolar.comthey/> > <http://www.icpsolar.comthey/> > Just searched eBay for "solar marine battery charger" and don't know what > I'm looking at. I'd leave it hooked up in the cockpit on the mooring. We > don't need much house power - just lights, radio, bilge and fresh water pump > - plus the starter battery for Universal M-18. Suggestions? > Tim > > > Even if the Coleman ones are end-of-life' d, there are a TON of solar > panels of all shapes, sizes, and wattage on eBay for cheap. > I had picked up a one-watt panel for about $6 (shipped, no less) to trickle > charge my car's battery during the week since I take public transit to work. > One watt is not much juice but I wanted to squeeze more life out of my > 5-year-old battery and that was a cheap way to go about it. Maybe next > winter will be the death's door for it...David > > > >
