hammet
Contributor
tbone,@almostDIR golf carts are typically 24v as an FYI. Reason being the amp draw is cut in half which makes all of the wiring much easier to manage. Electric golf carts are typically 3-5hp, so the right range for most smaller compressors, but to get that in 12v would be very difficult since you would first have to find a 12v motor that large. It is very uncommon to see a 12v motor larger than 1hp due to the amp draw.
Depending on the voltage of the solar system, it may be possible to wire the panels and battery banks to higher voltage which would allow DC drive in a reasonable range.
@NotWavingDrowning this project is possible if you are truly committed to do it. It is not recommended if you do not have significant experience with high current electrical systems and there is a very real possibility of a fire. Proceed with caution
Lots of cruising sailboats use banks of deep cycle golf cart batteries. They are usually 6v batteries that are paired in series to make 12 volts and the pairs then wired in parallel to produce 'house' banks of anywhere from about 100 amp hours to 800 Ah. The reason these batteries are used is because they are built to take many cycles of deep discharges (to about 50%) and recharges.
Once you have a decent size bank and a proper way to charge it, an inverter can be used to get AC current. Marine grade inverters over 1000 watts are commonly available, though pricey and they must have short, heavy cables to the batteries to prevent voltage drop. Assuming OP had a large enough battery bank, he could run the compressor, however, he is going to need a way to charge his battery bank quicker than just solar. Mostly, that means running is engine for while until his batteries are at about 80% charged and then topping off with solar. Not a realistic way to fill multiple tanks for multiple days of diving.
There is no way you can add over 1000 watts of solar to a sailboat inexpensively. 50 to 200 amps is much more realistic. First of all, the real estate is just not there. Secondly, the panels must be pointed directly at the sun to reach close to ideal output. Then there is the cost of the panels, controller, and wiring. Even the slightest shading (less than 5%) such as clouds or the shadow of a mast will cause a severe drop in output. Most cruising sailors will use solar to keep their battery banks topped off but they are using much fewer amps over periods of days. Maybe 100 amp hours if they use refrigeration. So panels that lie flat on the bimini of a boat may average only about 4 hours of directlight per day in the tropics and that's when it's sunny out.