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How many DC amps is too much
It is interesting to know how other boaters are selecting equipment
and managing electrical power on cruising sailboats. Standard production sailboats rarely have onboard DC power grids to support additional electrical loads. Most extended cruisers and live aboard boaters prefer to have conveniences like refrigeration microwave ovens, computers and creature comfort items. There must be a limit to how much daily electrical load that can be supported on a pleasure size extended cruising sailboat, but what is this limit? I believe that an average cruising boat's DC power consumption when at anchor might be at least 50 amp-hrs per day. If equipped with refrigerator add 10 amp-hours per cu. ft. of box per day. If additional 110 volt appliances are powered from an inverter the total power grid will be overstressed unless energy is generated from other than the a engine alternator. Here are some actual examples of cruising boats and how they managed their DC power grid. 1. Twenty seven ft sailboat two people onboard with one cylinder diesel crossed from England to Bahamas with no electrical system. Navagation lights powered by Diesel fuel flame three gallons total use of diesel in 27 days 2. Catalina 27 with two group 27 batteries 30 amp alternator on first cruise after installing refrigeration unit batteries dead after two days had to get a jump start from another boat. This problem was repeated each time boat was used. Running engine several hours a day did not solve this energy deficiency. 3. Thirty ft. sailboat two cylinder Yanmar engine with 60 amp alternator and 4 gulf cart batteries spends 6 weeks to 3 months each summer in Bahamas. Boat has standard basic electrical lights, VHF, and Adler Barbour refrigeration. With the help of two 80 watt solar panels mounted on top of Bimini engine only needs to be run every other day to recharge batteries. 4. Forty four ft sailboat world cruiser on trip from Ft Lauderdale to South Pacific. Boat equipped with both engine driven and 12 volt AB refrigeration systems were connected to large holding plate in refrigerator. I received a post card stating on 31 continuous days of sailing the wind generator supplied all power needed to charge batteries and operate refrigeration. 5. Local 36 ft sailboat with refrigeration tested in my book completed circle trip to England with wind generator supplying all energy needed on trip east bound, than lost generator overboard in English Channel during storm. 6. One of the best truly live aboard boats I have worked with is a 60 ft plus two mast sailboat with very large refrigerator and separate freezer. There is an engine driven refrigeration system freezing seven holding plated when motoring. There are two air cooled 12 volt refrigeration units maintaining box temperatures when boat is at anchor which is most of the time. There are several energy sources to support this boats DC power grid, two wind generators, solar panels, prop shaft alternator and engine alternator. 7. My own 32 ft Watkins sailboat consumes around 70 to 100 amp-hr per day when anchored out in summer tropical weather. I have a number of 110 volt fans running off an inverter and Yes I have Hybrid refrigeration Engine driven refrigeration and 12 volt system freezing three holding plates. I run the engine one hour per day to support my energy needs consuming about 1/3 of a gallon of fuel. If you want to see how my boat is equipped it is described on my web site at http://kollmann-marine.com/Loreli.htm 8. If you are following Skip's Morgan 46 adventures on Flying Pig you know his plan was to support all his electrical and refrigeration needs including heating water with 12 volt energy. Skip removed the engine driven refrigeration system replaced it with a 12 volt Frigoboat unit. The large generator was removed providing room for a battery bank. We are still not sure what his actual daily power needs are but he seems to be managing his energy budget by trimming down the load and running a small Honda generator when wind and solar power is not enough. One good piece of information Skip provided if I understand him correctly is the Hondo 2000 powering a 40 amp DC output charger can rum 6 hours on 1/2 gallon of gas. I have a 3000 watt generator that consumes 6 gallons per hour. |
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