Originally Posted by Newport41
Well this has brought up a few questions for me. First of all I'll let you know what I'm planning on here. We've got six Trojan T-105 golf cart batteries with a total (rated) capacity of 675ah. I don't want to run our poor old universal to charge the batteries. We have pretty minimal electronics. LED running lights and cabin lights, computer was designed with no moving parts and a 12'' LCD, small compressor/evaporator refer with interior closed cell foam inserts for extra insulation in the tropics, low draw fans, foot pumps for the sinks, monitor windvane, Raytheon sailing interments, small and simple GPS, and a conservative Furno radar. I figure our daily consumption at about 100ah. I know that these estimates are always low but I am assuming that we'll only use the windlass and electric autopilot when motoring or when we'll be motoring soon.
Your set-up fairly closely mirrors what we are putting together. Ideally, I want enough reserve to spend seven days or so without starting the engine for electrical generation, and with the assumption that I will get 8 hours of usable sun five days out of those seven. I don't expect to keep a full charge; I do expect to draw down multiple AGMs to 50-60% gradually on the basis of "three amps out/two amps in" logic.
I am not entirely convinced I need a wind generator...yet, because I have pipe "lifelines" and a pilothouse roof and will build an arch to hold panels, like Cruisingdad's, and an easily stripped-off bimini. So I might have enough surface area to just have solar as the top-up device. I am installing a Xantrex RS2000 charger-inverter by May or so, and will be able to start making "real-life consumption" estimates, even with just two Seavolt 6 VDCs and one 12 VDC start battery (all flooded lead-acid types). I will see what I eat and excrete, so to speak, with 30 amps of shore power, with a stock 55 amp alternator at cruising and motorsailing speeds, and on the hook with no charge available (haven't bought a Honda portable genset or panels yet).
This will be a start to establish where the investment in gear should go. But the goal is the same: a conservative use of total amps, plus the ability to generate from the sun (and perhaps the wind) enough of a surplus to keep us running the diesel for power as much as possible.