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
