Will Wants to Know About Electricity on Boats
Back on our Call for Crew post Will just asked about how electricity works when Mon Tiki leaves the dock for more than a few hours at a time. As it happens, right was Will was asking, I was breaking open the transformer on an IKEA LED light in the hopes of using it and others like it as interior lighting on Mon Tiki. I take this as a sign that greater forces are at work than just Will curiosity or my thrift.
EDITED TO ADD:
My friend Bob Wise is also thinking about electricity on boats today, which is concordant with my suspicion that greater forces are afoot!
So then, a post about how (in Will’s words) “How does electricity provisions work on trips like this?”
First lets talk about what electricity might be used for on a boat like Mon Tiki. In no particular order electricity might be used for: starting engines, navigation instruments (GPS, radar, depth finder), communication instruments (radios, AIS), navigation lights, bilge pumps, interior lighting, refrigeration, monitoring systems.
Now let’s think about how that electricity might be provided. It could come from an alternator mounted on an engine, from a generator independent of the engine, from a wind turbine, from a water turbine, from solar panels, or from shore-power.
Now let’s remember that if the boat is not getting electricity from shore-power, a alternator on a running engine, or a generator, it’s going to need a place to store electricity, and that place is going to be some sort of battery bank. This bank might be as simple as the start-battery of an engine, or it might be a larger collection of batteries. More batteries can store more electricity, but more batteries are more costly, heavier and take up room on the boat, and no matter how much you can store, you have to get it from somewhere.
On INTEMPERANCE we had three ways to make electricity. We had the alternator on the engine, 120 watts of solar generation, and 400 watts of wind generation and our storage capacity was roughly equivalent to 4 large auto batteries.
On my 2009 trip from Montauk to Bermuda (7 days) and then Bermuda to San Marteen (9 days), the trip from St. Croix to Montauk (14 days) and the roughly seven months of living on the boat in between I never felt the need to start the engine to recharge the batteries. We were thoughtful about our usage and sometimes would put off charging a laptop or watching a DVD until the morning (solar panels work best in the daytime) but we were never compelled by issues of safety to use the engine to make electricity.
Mon Tiki is not yet equipped with electricity making capacity beyond the alternators on each of her two outboards. She has a start battery for each outboard, plus an extra storage battery (these were salvaged off INTEMPERANCE after she burned.)
Mon Tiki is not yet equipped in a way that uses a lot of electricity. As with all other chip-based technology, Mon Tiki’s navigation and communications equipment is an order of magnitude more powerful and more energy efficient than INTEMPERANCE’s. At present Mon Tiki has no interior lighting beyond a few cleverly placed LED flashlights, and Mon Tiki has no refrigeration.
Mon Tiki also has no electrical usage monitoring equipment, so part of what I learned on our run from Montauk to Norfolk is that Mon Tiki can go for 24 hours of “full usage”, that’s nav instruments, comms, radar, nav lights at night, and heavy auto pilot usage and still have enough reserve power in the batteries for the engines to start right up. (Being small outboards, they can also be pull-started if the batteries are flat.)
Charging for devices is accomplish via a cigarette-lighter style socket that taps Mon Tiki’s 12 volt system and a USB adaptor. The drain to charge an iPhone or iPod is trivial, especially if it’s done while the outboards are running.
There is also a 1500 watt inverter onboard. This can be tapped into the 12vDC system to produce 110vAC, but the conversion from 12vDC to 110vAC is inefficient and produces a large drain on the power system so it is not a first choice for making AC. Fortunately there’s not much call for 110vAC on a boat like Mon Tiki. All of her systems are 12vDC.
On the run from Norfolk through the ICW to Beaufort the route twists and turns though the marshes and swamps and the wind won’t always be from a favorable direction. I expect we’ll use the engines at least a couple hours each day, so there will be plenty of electricity.
One of the projects for the winter is to finish out Mon Tiki’s interior for family cruising, including lights in the cabins, refrigeration in the galley, and a electrical system that can support and monitor that sort of usage. Solar panels continue to get more powerful and less expensive, down to about $1.25/watt. I won’t be surprised if Mon Tiki has a 400 watt array mounted when she sails back into Montauk Harbor next year.
One more thing about electricity. What I learned in my time off the grid is that fresh water ends up being a more limiting factor to how long you can stay out than electricity. The cost of desalination gear has fallen, but it still takes a lot of power to turn salt water into drinking water, and shit happens.
Two years ago, friends returning from Hawaii after the Transpac on a boat just like Intemperance lost their electricity making capacity, which took out their water-making capacity. They were able to jury-rig their power generation to give them a few minutes of outbound satellite phone communication each day, but they ended up on very tight water restriction for the duration of the trip.