{"id":18383,"date":"2011-10-16T17:01:31","date_gmt":"2011-10-16T22:01:31","guid":{"rendered":"https:\/\/setsail.com\/?p=18383"},"modified":"2012-02-15T12:47:00","modified_gmt":"2012-02-15T17:47:00","slug":"fpb-64-systems","status":"publish","type":"post","link":"https:\/\/setsail.com\/fpb-64-systems\/","title":{"rendered":"FPB 64 – Systems"},"content":{"rendered":"
The engineering concept we use today has its beginnings in the 1980s.<\/span><\/p>\n <\/p>\n It was on the prototype sailing design\u00a0Sundeer<\/em> where we first used “traction” batteries, as the foundation upon which the rest of our approach to systems is built.<\/span><\/p>\n Since then, we have continually refined this approach. With the FPB 83 Wind Horse<\/em> we have combined our tried and true DC side of the equation with the latest inverter technology for a highly efficient end result. The FPB 64 approach to systems is almost identical to the FPB 83, with a couple of refinements thrown in (for lots more details on how the FPB 83’s systems are designed see the sidebar, or click here<\/a>. <\/span><\/p>\n The bottom line to this approach is robustness, reliability, and simplicity as a foundation. We then toss in a dose of redundancy – we do not want our cruising interrupted because of systems problems. What follows is based on these principles.<\/span><\/p>\n DC System Overview<\/strong><\/span><\/p>\n As previously indicated, our DC systems are based on a huge bank of “traction” batteries.<\/span><\/p>\n They are charged while underway with specially built alternators running off the PTO on the main engine. At anchor the inverter\/charger system can charge the batteries if the generator is running (or you are connected to shorepower). <\/span><\/p>\n This system allows long periods of quiet time without the frequent use of the generator, and eliminates the need to use the genset for air conditioning and most other AC loads when you are underway (resulting in a quieter, more fuel-efficient environment).<\/span><\/span><\/p>\n Batteries<\/strong><\/span><\/p>\n The main battery bank is made up of individual 2.2 volt “traction” battery cells designed for long life with deep discharge. The normal guarantee is for 1200 80% discharge cycles<\/em>. What this means in our application is many times this number since full discharges are rare and the shallower the discharge the more cycles you get (for example, a 50% discharge rate typically increases available cycles to 3000 or more).<\/span><\/p>\n These batteries are typically used in electric trucks, and for emergency power supplies for utilities. They have a very low rate of self discharge, and if taken care of, will last 10 or more years (manufacturers claim double this).<\/span><\/p>\n There’s an important factor about traction battery capacity upon which we need to dwell. Think about how these compare to normal deep cycle batteries. Most experts suggest not taking your batteries deeper than a 50% discharge cycle, or their useful life is dramatically shortened. The top 15% of capacity is only going to be put back when you are on shore power, or motoring for long periods (that last little bit goes in very slowly). So in the average marine application, you have a useful capacity equal to at most 35% of the 20 amp hour rating.<\/span><\/p>\n Now compare this to our traction batteries. Their useful capacity is 80% fully charged, or 65% if you leave off the top 15%. That’s almost twice the useful capacity of conventional deep cycle batteries<\/em>. Unfortunately, it is very difficult to retrofit this type of battery. They take room, are heavy, and need to be careful restrained. You have to design for their incorporation into your systems from the beginning.<\/span><\/p>\n Which is why we have been using this approach for almost two decades.<\/span><\/p>\n<\/div>\n Based on our experience with the FPB 83, we know that electrical consumption has crept up compared to what we were used to just a few years ago with sail. Using home style big screen TV, lots of electrical appliances in the galley, often two computers (and one with a second monitor), and soft lighting, really eats the amp hours. Switching to mainly electric cooking in the galley, mostly done with inverter power, further adds to the amp hour burn rate. Which is why we specify a 1400 hour, 24-volt traction battery capacity (C20 rating). On the assumption that the genset was run every second day for a couple of hours while a major meal was prepared with lots of oven time (at the same the laundry is going), you could probably hang out for a week or two without using the genset specifically to charge the batteries, or heading somewhere new (whence the engine alternators would charge you back up). That short genset run every other day will give you back a third to half of the amps you have used (the inverters\/chargers take all excess genset capacity and use it to charge the house bank).<\/span><\/p>\n These individual cells are big: 8.5″ x 10.9″ x 28″ (215 x 277 x 710mm) each. They each weigh 194 pounds (88kg). And there are 12 cells in the house bank. As big as they are, a couple of guys can get them into place where they can be lifted in\/out through the salon hatch with a small crane. In the unlikely event of a cell failure, you replace the bad cell, not the entire bank. And this is an industry standard size, available in most of first world from a variety of manufacturers.<\/span><\/p>\n Bottom line: you cannot fit a better battery system to this boat.<\/span><\/p>\n For lots more details on this subject see the battery chapter in our Offshore Cruising Encyclopedia<\/em> starting on page 858.<\/span><\/p>\n Alternators<\/strong><\/span><\/p>\n If you have a big battery bank, you need a powerful charging source to provide the necessary minimum charge rate. This means large alternators running at full output for many hours. Normal alternators become extremely hot in this type of application and quickly fail from overheating.<\/span><\/p>\n<\/div>\n The alternators we have been using for the past two decades, made specifically for us by Electrodyne, are rated for full field output. The will deliver 150 amps\/28V charging rate for hours, and stay relatively cool.<\/span><\/p>\n One of the secrets used is to remove the diodes from the alternator case. These are mounted in a remote, fan-cooled, rectifier assembly. That is what the center and right hand devices are in the photo above.<\/span><\/p>\n<\/a><\/p>\n
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