Solar Charging
You can get a small solar charger at Harbor Freight Tools for about $12. I put one on my camper to maintain the battery while it's in storage ... works well.
On my Ericson 38 which we cruise to the Bahamas each winter for 6 months, we have a Kyocera KC120 120 watt solar panel. I wish I had bought two of them. They're not sold anymore. The jury is still out on whether to add a wind generator.
Anyway, we run a lot of stuff on our boat. Adler-Barbour air cooled fridge, sat phone, sat radio, SSB, VHF, fans, lots of lights, radar, below decks autopilot, computer, TV, two GPSs, vacuum cleaner, various tools, etc. We've replaced the lights we use the most with fluorescents. I get ice in my sundowner every evening.
I also have put a lot of thought into our 12v system and lots of work rewiring everything. I run two Group 31 Gel-cells as a house bank (190 amp hours) and a group 24 gel-cell starting battery. I installed a Xantrex TM-500 battery monitor, upgraded all the cables, use a West battery combiner to charge the start battery, installed a Blue Seas master switch panel, Xantrex 40 amp shore power charger, Xantrex Pro 1800 inverter, Balmar 65 amp alternator with Smart Regulator. The solar panel feeds through a 15amp controller.
When cruising we always motor sail to provide power for everything. When we're anchored we end up running the engine between an hour and two hours a day. Overnight, we typically end up with battery voltage about 12.4-12.6v and the accumulated amp hours used is typically 50 to 70 probably depending on the sun from the day before. Generally I stop the engine when we've recovered the 50-70 amp hours and the voltage is at least 14. The regulator(s) are all set at a max of 14.1 to avoid boiling out the electrolyte.
I have an old spare alternator that's about 110 amps that fits our 5432 installation and I'm thinking about swapping it for the Balmar to reduce our engine run times. The Gel-cells will accept charging rates at up to 50% of capacity (bulk rate) so the initial charging at least could go faster with the big alternator.
I'll likely buy AGM batteries next time around since they offer 105 amp hour capacity in the same size case. The batteries I have are dated 2000 and we've owned the boat 4 years now so I'll likely need to bite the bullet soon. (how can you tell before they fail?)
During the day with bright sun on the panel, the best I've seen on the battery monitor is about 7 amps but that figure is net of whatever is running at the time and of course winter solar angles are lower. By dark when we start using lights, the net amp hours used is typically less than 10 and often is zero. So what that means is that during the day, our solar panel keeps up with our demand pretty much. Consider that we run the engine first thing in the morning so the solar panel is starting from a fully charged (or nearly so) position.
Many people are amazed that we get by with less than 200 amp hours of batteries. Most cruisers I know have massive 400-800 amp hour house banks.
IMHO the only thing they gain with bigger battery banks is that they can go longer between charges. Instead of an hour each day, they can postpone charging for a few days but then they have more amp hours to recover and so run longer. Of course, wind generators and/or more solar panels change that equation.
Uhhh, what was the question?
Oh yeah, if you cruise like we do, a good solar set-up is hard to beat. I wish we had 200-250 watts. If you need more than that, and you sail where the wind blows pretty steady, think about a wind generator. I'm not a fan of wind power ... I think they add complexity, noise, and lots of drag but what do I know. Keep in mind that a wind generator won't be very effective while sailing but then we spend most of our time at anchor anyway.
If you just want to maintain a fully charged battery bank between weekends, go for the smallest, cheapest, plug-in solar panel/charger going.
