Hmm! The VHF should draw the same, or likely less, power than a stereo system if it's mostly used for listening; the real power draw is when transmitting. So, if that's not common, (or you use the VHF in "local" or low power mode) then that's probably equal or less to a regular stereo system. Especially since you're not kicking a massive subwoofer to crank the tunes. ;-)
You didn't mention the frequency of usage. eg., are you on board daily or 2x a week or what. I'll assume three times a week; in this case, I think you can probably do with a 20 or 30 watt solar kit, if it's out in full daylight when you're not onboard. This is because the solar kit will have several days a week with your electrical panel essentially shut off, no draw to speak of. The prices I saw for this are much more reasonable. Personally I won't do that since I'm in Chicago and dockside thieves are not unheard of, though the generally won't break into the cabin. (My boat hook pole hasn't disappeared in 8 years despite always being stored above deck.) You mentioned losing cranking power. On Persephone, we designate one of our two batteries for the engine, and one for house. Our power needs are very modest since anytime we need serious energy we can hook up to shore power. Perhaps such an idea will help secure your thinking? Designate a single battery to engine start? I suggest firstly designating a battery only for engine starts, and a separate for house use. Adding LED lamps (such as from Dr. LED) might eliminate the need for the inconvenience of flashlights. You mentioned "several weeks on the mooring" -- perhaps a low wattage solar panel will help you top off and keep maintained a battery bank while you are not on board, as long as it is weatherproofed. That could be as simple as turning off every electrical panel switch and cutting the "I'm alive!" light on the electrical panel so it doesn't draw juice, and plugging in a cigarette-lighter panel and routing its cable out the cockpit so the panel is in direct sunlight. That, of course, can be made unneccisary (sp?) with a solar panel AND a charge controller. Personally, I wish I had bought LED lights for my mast when we had the mast down, and for the navigation lights, and for the cabin, but we had too many other expenses to make that feasible. David On Tue, Apr 13, 2010 at 6:25 PM, Tim Millar <[email protected]>wrote: > > > David, > > I meant a VHF radio, not AM/FM/CD - the kids all have their iPods<G>. The > kids are pretty good about light discipline; they all use flashlights. But > LEDs are something to consider in the main cabin - I'll take an inventory of > all the fixtures at our work party tomorrow. > > Daytime use is minimal with no electronics, just the VHF, no refrigeration > or fancy stuff. In Nantucket Sound GPS and VHF handhelds would cover us in a > pinch, and I always carry fresh spare batteries. I do worry, however, that > the Perko won't get switched off and we lose cranking power after a few days > or a couple of weeks on the mooring. I do have a power pack that I take with > us as backup, but a simple and reliable way to keep the charge up would give > me great peace of mind. > > Thanks for your thoughts and calculations. > > Tim > > > > > As a matter of fact, the 1W panel I've got is marked with the ICP Global > logo and website address. Nice coincidence. > > I'm not an expert -- I'm good with electronics but it's mostly from the > gut, not from any formal education -- but it seems to me you are looking at > a few amps per hour of constant draw (lights, radio) and a few amps per hour > of intermittant draw (the pumps). The biggest draw is probably the lighting, > if you are using traditional halogen / incandescent bulbs; unless you like > your music loud and kickin' the radio will probably stay under an amp. The > pumps will draw several amps apiece when running. > > Considering that 1 amp (at 12 volts) is 12 watts, this can quickly get > expensive for solar rigs that can keep you topped off. (Amps times volts = > watts.) If you are on your boat daily you'll want something to take > advantage of the daylight hours to replenish the battery usage nighttime; if > you're onboard twice a week, you can probably get away with something > smaller. Note that I'm not taking into consideration running the engine to > charge the batteries in this line of thinking. > > In the worse case, let's say you live aboard, meaning constant draw. You'd > want to get a kit that can provide several amps more than what you draw > during the day. Let's say an average draw, daytime (radio, pumps) adds up to > 3 amps on average; I'd personally look to get a kit that can provide 5 amps > of charging power. 5 amps x 12v = 60 watts. This way you cover your daytime > power needs via solar energy and have leftover juice to feed the batteries > for nighttime use. Systems of 60 watts cost a lot of money! You definitely > want to consider how often you'll draw power and consider that against how > large a system you want. > > Just as a side note: I think my stock '88 Universal M-18 has a 55 amp > alternator. That's 660 watts! If I needed to run the engine an hour a day, > I'd invest in something that can provide 660 watts over 10 hours of > daylight, or 66 watts per hour. There are so many factors to consider it > feels more like an art than a science to me. Weather, usage, engine time & > alternator size, etc. > > One last thought: Have you considered LED bulbs for lights? They are quite > pricey but these lights will probably outlast our children, and they draw > 1/10th of the power for the same lumens. It's a huge improvement in battery > conservation. > > David > > > >
