You may have seen on our Instagram that Sargo is now out of the water for the winter. We are actually excited about that – as we have lots of projects to do in order to get ready to move aboard and set sail next summer. The biggest project we have to accomplish is an upgrade to her electrical system.
Sargo is going to be 100% off-grid. Unlike most boats, we cannot plug into “shore power” if we stay at a marina. That means we’ll need to produce and store all the power we need. Sargo is going to be her own power plant and Bjorn and I are the chief engineers. We have a lot to learn. Currently, we are doing lots of reading, and talking to friends and experts. I even took a weekend workshop for women through the Women’s Sailing Association on Marine Electrical Systems! Without getting too technical- below is a description of the system we are designing and installing on Sargo.
Power usage – we’ll need electricity just like a house does. However, most of the electrical needs on Sargo are actually 12 Volt DC (unlike at home – where we use 110 Volt AC). Sargo actually has 12V DC circuits, 110V AC and even 220V AC (European system - she was made in France). But in all cases, the power comes off our battery bank. One of our first steps in designing our electrical upgrade was to figure out how much power we’ll need in a day. Here’s a link to our Excel Spreadsheet we created to estimate our power needs. It’s looking like our 24-hour energy usage will be between 150 amp/hrs while the boat is anchored – and up to 500 amp hours while doing a passage and running the boat day and night. (Simply put Amp hours is a good metric for measuring the volume of energy used over a period of time). Some of our biggest energy hogs on Sargo are the refrigerator, freezer, autopilot and keeping our electronics charged – laptops, ipads and phones. If we add any “home style appliances” such as my beloved Vitamix blender we will need much more! If you’re wondering if you can use your [insert household appliance] on your boat check out this blog post.
Power Storage –As mentioned above, Sargo’s power will be drawn from a battery bank. We’ve chosen, for multiple reasons, to install Firefly Carbon Foam batteries – 6 of them in fact to create 900 amp hours of power. But batteries being batteries – we can’t actually use that much of the power – a rule of thumb is that you can only use about 50% of your battery capacity – so we have about 450 amp hours available. The Fireflies can actually do better than that but let’s keep it simple. This means we can use about 450 amp hours of energy without putting any back into the batteries before we start damaging the batteries by drawing them down too low. Therefore on most days we can go 24 hours without making any additional power. But after than – it’s time to charge up.
Power Generation – We will be able to generate power to charge our batteries three different ways. Solar panels, an engine alternator, and a portable generator. We are currently leaning toward 2- 330 Watt Panasonic commercial house panels. We have that option since we can mount rigid panels on our stern arch – many sailboats need to use specific marine panels that are flexible or can we walked on which are smaller and more expensive. The two large Panasonic panels equate to 660 watts of solar – converting that back to amp hours and considering how many hours a day the sun shines – we can expect about 200 amp hours of charging into our batteries on a decently sunny day. This should meet our power needs on most days. However, we’ll inevitably have rainy days and days where our energy usage is above the power coming in from our solar panels. In order, to recharge our batteries beyond the solar panels, we can run Sargo’s engine. When the engine is running and the batteries are not fully charged, the alternator (attached to the engine) operates to generate electricity and store it in our battery bank. In general, the lower our batteries and the higher the RPMs we are running the engine at the more AMPs we can put into our battery – up to a maximum of 120 AMPS per hour based on our alternator rating. That means with just our engine alone it would take a good two hours to generate the 200 Amp hours we expect to use. If we’re moving the boat to someplace new – 2 hours of running the engine won’t be a big deal. However, if we are at anchor we can choose to run a portable generator which will produce similar battery charging capabilities as our engine. We are considering upgrading our alternator – but that’s a whole other story.
There are a million other nuances that I’ll spare you from that include the need for smart regulators between our power generating items and our batteries that make sure they get charge correctly. We also have two other battery banks (starter batteries to only start the engine, and batteries to run our bowthruster and anchor windlass). But I think you get the point – a boat like Sargo is COMPLICATED. Anyone of these can break or malfunction and really put a damper on our day to say the least. Bjorn and I are in the process of learning as much as we can in order to get Sargo’s systems working well in a way that we can troubleshoot and (hopefully) occasionally fix.