Managing power on a cruising boat

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.

16 Responses

    1. Another costly (aren’t they all costly) improvement, but it will make a big difference, would be to change the fridge insulation, or build a new box or whatever. Good thick, well sealed fridge insulation makes a big difference to the cycling of the fridge.

  1. You guys have about the same specs as us. We’ve got 4 300-aH 6V AGMs for a 600aH house bank. We have 36-year-old refer insulation that ain’t working. We’re in the tropics. We have wind, but no wind generators. We have no genset. We bought Del Viento with 2 100W panels and then added a 120W panel. With that configuration, we have nearly been keeping up with our power consumption, proactively tilting the panels and running the engine for 3-4 hours every 10 days or so. But I am now in the process of installing 2 additional 55W panels that will bring our total up to 480W and should render us self sufficient so long as the clouds stay away. Though one full day or night off the boat makes a big difference too, allowing our bank to catch up without the power-hungry humans around. Michael

    1. It’s interesting how similar the specs are! Wasn’t it great up in the Salish sea and Alaska when your refrigerator could keep up with everything in that cold water?! At least, that’s how it went for us (and that’s with air cooled refrigeration). It just didn’t have to work as hard. Curious why you are going for more solar instead of adding wind to the mix, since as you say, you *have* wind- and the clouds don’t always stay away. With the last year of less sun, less wind, and declining batteries- we had to run the engine progressively more. Diesel engines really don’t like being used without a load, so we opted to get a portable Honda2000 generator late last year. I liked being generator-free, but it’s been a better for us than adding hours to the Yanmar- and vastly more fuel efficient way to keep the batteries going. I’m really hoping we’ll be able to stash that thing once the green power additions are installed.

    2. And in the Salish Sea, we motored more than sailed; as a byproduct, power was always plentiful. Why more solar over wind? Mostly cost, 2000 pesos for these two additional used Siemens panels.

  2. Hello Behan,
    We have a Gulfstar 50. 6 Trojan T105s 6v, two 190 watt solar panels mounted on a hard top bimini (yes, it does get some shading during the day) and a Honda 2000 which we rarely use as we motor an hour or two a day in our travels. Would love to get a wind generator but it probably does not make sense in the Northeast, will wait until topics are on the horizon. Will be very interested to hear how you chose the Silentwind and how it meets your expectations. Jonathan s/v Calypso

  3. Hi Behan,
    I must say – I have loved reading your blog these past years. Absolutely fantastic! I’m from the PNW as well and I’ll be taking a year off with my wife and kids to cruise in the relatively near future. Your blog has given me so much to think about and provides a glimpse of what ‘might be’….
    I’m sure you have a wealth of knowledge on the solar upgrade project, but thought I would just forward along a couple of resources that I found beneficial when putting together our own system. Much is fundamental-type stuff…but just in case there’s something useful for you guys:
    1. This is from an RV’ing perspective, and is very opinionated, but the foundations and the keys to real success are all in there.
    2. This site is from one of the most knowledgeable people I have come across in boating. His articles and how-to’s are likely familiar to you if you follow the Sailboatowners or Cruisers Forum sites….but if not – there will be a wealth of info on charge controllers, battery health, solar setups, wiring connections, alternators, and on and on….

    I hope something in there is useful to you.
    Best wishes and sincere thanks to all the effort you put in with the blog.
    Mike. s/v Aja

  4. Behan,
    Michael took a day off work last week and purchased and replaced all the batteries on our Morgan.
    One for the generator, one for the Yanmar, and 8 for storage.
    It was a long, back wrenching day for Michael…. and costly!
    Janet Lee Knizner-Enders, S/V AdventureUS2

    1. We feel his pain. And by we, I mean Jamie! I, well, supervised. and made lunch. Another cruiser with better upper body strength 🙂 helped him get them to the boat and on board… thank goodness for davits that swing out! The only way we could lift them on.

  5. Hey Behan. We have 645 watts of panels on the rooftop that have us almost sustainable. Our big issue are batteries, which are slowly (but more quickly, now) starting to nosedive. They’re 630 AH Lifeline AGMs. Charter standard for Moorings, and pretty beat after only 5 years. Looks like we’ll have to replace those in Tahiti. Ugh. Oh well. Once we do, though, we should be in good shape. We run our engines to power the watermaker, usually. Our main culprits for power drain, though, mirror yours: refrigeration and computers.

    1. nice solar capacity! That’s fantastic. Batteries… yes, a pain. We were afraid ours were nosediving a few months ago but have eked out more time. Five years is a great life for most boat batteries – those must be good! Will you look at lithiums? We were very tempted, and they’re definitely the best value per lifetime / amp, but it included cascading projects and costs we weren’t ready for.

  6. Hi Behan, how long did your battery bank last? Do you equalize? I need to replace the battery bank in my yacht and am considering to switch from Flooded Cell to AGM. But am concerned AGMs may require more sophisticated maintenance than Flooded Cell. I have read articles that mention monthly equalization, split banks and chargers, careful voltage control during charging cycles (including reprograming chargers and regulators). Would love to hear your thoughts ! Best Regards, Alex

    1. Hi Alex- Jamie here. Our Lifeline AGMs lasted 5-1/2 years – better than average. If we had more capacity it could have been even longer, because we wouldn’t cycled as deeply (always kept above 55%, usually above 65%).

      We like AGMs because they are no maintenance, are not any more voltage sensitive than lead-acid, and there’s no venting required – so perhaps a safer choice. Also, you do not equalize AGM batteries that I know of. Is it possible that you confuse AGM with gel cells, which are very voltage sensitive?

      With AGMs, and all marine batteries, you want a good multiple stage charger and voltage regulator for the alternator. If charger or voltage regulator do not have an AGM algorithm, they are likely older and maybe okay – or may not even have multiple charge cycles. Most importantly, watch the voltage. Battery management devices are nice, but watching voltage is like taking blood pressure of a patient. Understand what bulk, absorption, and float charges voltages the battery is rated for – then observe what your charging sources are actually doing. Many bulk charge modes drop to absorption well before reaching the peak voltage leaving batteries to linger at lesser states of charge – which will over time lead to sulfation and reduced charge memory.

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