Battery type/capacity and how much solar power seem to be generating almost as much fun as anchoring
For ten years we have had solar on our boat. During that time we have cut our consumption
from 175 to 75 amp hours per 24 hour cycle.
Nigel Calder has a nice section in his Mech and Elect Handbook that outlines how to determine your daily usage. It's a good place to start.
We have a keel
cooled fridge (the Frigoboat unit), all LED lighting
, changed the laptop
to a SSD (and the current laptop
draws <65watts while on and charging). We watch video on our 15.6" laptop screens, which double as chartplotters. They plug
into the stereo easily. We have stayed with foot pump water
, use an AIS
unit in our VHF
, no radar
We use the 36 cell panels (a pair of Kyocera
85watt) into a Blue Sky MPPT
controller. I think the new version (3000i) has a second output on the controller. They charge four (2 pairs) of Lifeline group 31 AGM batteries.
We can go at least a week in the Pacific NW winter without hitting 12.2 volts. During the summer we have plenty of power. In warm water
(75-80) and hot air (90+) on the east coast
, we topped out at about 90-100 amps per day due to the fridge (16-20 aH cool to 36-40aH in hot weather) and extra fans.
The AGM batteries on our boat replaced gels that lasted 9.5 years. We went with these batteries because they will take the full output of our alternator
(12si rebuilt to 108amps), which is limited by our regulator
to about 80 amps, until almost fully charged. I was very pleased to find that this matched the Lifeline claim, but was disputed by many people I know in the industry. I checked this with a meter a couple of times. But we don't really need to rely on that because of our usage.
In winter we go into deficit by about 25 amp hours per day. Our battery banks total 420, with 210 above the 50% level. We actually see an average of 50+ amps per day from our solar.
If we added radar
we would need more. To do that we would need some sort of arch on the stern for the extra panels. Then I'd probably put up three 145-150 watt panels. The arch costs as much as the radar!
During our examination of electrical
components we found some interesting things. Our old propane
solenoid drew 500ma, our new one 250ma. The MPPT controller we use is not the most sophisticated one, but it uses a fraction of the power my first choice (an Outback unit). The electrical system
is really just that, an interconnected whole. If we add radar (or a watermaker) we would then need more panels (and mounting system), a new controller, some new wiring
I am in the industry, helped scores of people with similar systems, and have found there is no one solution. The balance of use and power generation is different for everyone. That said, a well thought out reduction of demand, and a good solar installation
makes things much better!