Managing power on a cruising boat

1 Apr
paddling home, racing the sun

Living off the grid, providing your own power, is a tremendous feeling. On Totem, it’s one of the compelling aspects of life afloat, hand in hand with a more simple life and a lighter carbon footprint. Relying on our solar panels and wind turbine to supply power needs instead of plugging in is liberating.

That good juice from the sun and the wind is stored in our house battery bank. Currently, that bank has 660 amps total from six 220aH 6v AGM batteries.  When we have steady trade winds, and sunny days, these meet our needs pretty well. For a long stretch, that’s been enough. We’re all power-watching hounds: even the kids understand the numbers on our electrical panel that show the voltage level in the house bank, and the net amperage being used or added at any given time.

Lately,  we’re falling short on power needs. Part of it is generation. Part of it is use. Part of it is storage.

On the generation side: as it happens, the equatorial zone where we find ourselves often has a lot of clouds- part of this whole convergence zone thing that produces squalls that increase seasonally, as they are now. Not great for solar power generation. It turns out isn’t known for having a lot of wind, either (you’ve heard of the doldrums?). There are windy squalls, yes, but they don’t last long; the steady trades aren’t here. The moniker “land below the wind” is well earned. We do have wind and sun and make power from both, just not at the level we’d like- but that’s relatively short term. Once we leave these low latitudes, we can more consistently generate green power.

On the usage front: we’re simply using more energy now than we were back in 2008. Our biggest power hog is the refrigeration, which suffers mightily in the tropics: the 32 year old insulation is ineffective. Our needs are changing, too. As the kids get older, we’re losing more power to the #2 use after refrigeration: digital devices, primarily powering computers. That’s not going to change, so we have to.

On the storage side: Totem’s house battery bank has been declining for a year. When marine batteries start to go, it’s possible to have a slow demise, but things can happen very very quickly. For a while, it was worrisome- juggling a lot of different projects on the boat, we weren’t sure when we’d be able to have the magic nexus of time and money to get a new set of batteries installed… but we had to. You don’t get a card to Pass Go wait once the batteries are dead.

The next few months are bringing a really exciting trifecta of power change to Totem. I never thought twice about our power use when we had a conventional land life, but I am positively tingly thinking about what’s coming up:

1. A Silentwind wind generator will soon significantly upgrade Totem’s wind power capability.
2. We are adding a solar panel. I big hearkin’ panel. It will double our solar-powered amps.
3. New batteries to replace our house bank are on on the way, and will increase our capacity by 50%.

This is huge. It’s going to take some work, but nothing we (or any self-sufficient cruiser) can’t handle, from building the box to hold the 600+ pounds of new batteries to installing the turbine and panels and wiring everything up.

What do you want to know about power on board? Who has solar, wind, or generators helping meet their needs? In the coming weeks, I’m going to get into detail on the work we’re doing and the changes that are happening to our own mini power grid, and want to make it as useful as possible.

Green energy fans like the Totem crew always like to read these posts on the Sailfeed website.

This article was syndicated from S/V Totem - a family sailing the world


  1. 2late2turnbacknow

    Behan Gifford, The flow turning the alternator would be supplied via a thru-hull. That’s the big question. Will the thru hull provide enough grunt to start the alternator(about 800 rpm).
    Your electrical system upgrades appear to be very well thought out, and you have the cooperation of crew to make it work.

  2. Behan Gifford

    * Helen- Lithium is a great way to go! Not in our budget this time around, maybe next time.
    * 2late2turnbacknow- not quite following you there, is the flow to turn the alternator just coming from the force of water as the boat moves at anchor?

  3. 2late2turnbacknow

    We were trying to figure out if a 1 1/2 or 2 inch through-hull could possibly provide enough flow to push a trash pump impeller fast enough to in-turn rotate a belt/pulley system attached to an alternator. Whew, that was a long sentence. The system would privide continuous charging while at anchor. Sounds like alot of fabrication and a low rpm alternator requires about 800 rpm to reach funtionality. If it works, we’ll let ya know.

  4. Tom

    Our web site has lots of information that may be helpful to you in determining your power requirements and managing you solar power.

  5. Helen

    We are building a new catamaran with 800 w solar and a wind generator.all LED lights and Engle freezer…1600 amh lithium Iron LiFePo4 batteries. ..alternator off the engine as the charger.

  6. Behan - s/v Totem

    Hi Cameron! We relied on our engine/alternator for chargering when sun and wind don’t do enough for most of the last 5 years. With aging batteries and lower effective capacity, we bought a Honda2000 as an alternate charging source to keep hours down on the Yanmar. We do have a high output alternator (it’s 120 amp). The boat isn’t completely switched to LEDs, but most of the way there! Only a couple of lights left. We try to charge everything via 12v, and I think it’s literally just our camera battery chargers that require 110+inverter.

  7. Jay Campbell

    Great stuff! Here on Largo we have 6 panels up top, all 250 watt Kyoceras, and 16 Gp 31 AGM batteries for a house bank, providing 12 v but also 120 v through a Freedom 3,000 inverter. We can run one air conditioner for 8-10 hours and the rest of the boat as well. We can also charge the bank with our engine alternators or either of 2 generators. – Jay and Karen Campbell on Largo, Palmetto, Florida.

  8. Cameron Vawter

    It would be great to know how much you rely on your alternator and whether your using a high power alternator? Where are your panels located? Have you switched completely over to LED’s? Do you charge electronics using 12 volt or via 110 and an inverter? Thanks for the awesome blog!

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