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Old 20-07-2019, 10:29   #1
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Electrical resiliency for Atlantic crossing

I'm preparing my boat for an Atlantic crossing (northern route) next summer. Lately I've been thinking about our electrical resiliency and I'm curious to hear from others who have made ocean crossings.

We have about 1kw of battery capacity supported by 350w of solar panels and our engine with a single alternator. Navigational equipment, electric autopilot, fridge, and freezer are our largest electrical loads. With normal sunlight, we will deplete our battery bank in about 5 days if we don't run the engine on a passage.

I consider our engine (1988 Perkins 4-108) to be fairly unreliable. If it fails halfway through the trip, or if the charging equipment related to the engine fails, then we will have to choose which electrical systems to sacrifice to maintain power for the remainder of the voyage. We would most likely turn off the fridge and freezer, some of our nav equipment, and hand steer during the day. That should reduce our electrical draw enough to run our critical systems with solar alone.

How long could you maintain electrical power without your engine? Is this an acceptable level of risk? We will install a second alternator and (most likely) a Monitor windvane before we depart, which will significantly improve our electrical resiliency.

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Old 20-07-2019, 10:36   #2
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Re: Electrical resiliency for Atlantic crossing

It is difficult to even begin to answer your question without knowing your energy budget and the individual contributions of each of your charging sources.
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Old 20-07-2019, 10:43   #3
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Re: Electrical resiliency for Atlantic crossing

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Originally Posted by Stu Jackson View Post
It is difficult to even begin to answer your question without knowing your energy budget and the individual contributions of each of your charging sources.
I don't know the exact numbers offhand, I average about a 12amp/hr draw when on passage, with solar offsetting about 10amps/hr during the day. That comes out to a deficit of about 150 amp/hrs per 24 hours that I make up with the engine. With only solar panels (~140 amp/hr/day), I could operate essential navigational equipment (including AIS but not radar) indefinitely. Depending on the sea state I could use the electric autopilot for about 8 hours per day. Of course, if I was only 3 days away from landfall, this would not be a problem with my large battery bank.

I'm interested to hear if other cruisers rely on their engine for some of their charging needs, or if most have developed other strategies.
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Old 20-07-2019, 12:53   #4
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Re: Electrical resiliency for Atlantic crossing

Look at efoys as your backup power.
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Old 20-07-2019, 14:43   #5
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Re: Electrical resiliency for Atlantic crossing

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We have about 1kw of battery capacity supported by 350w of solar panels and our engine with a single alternator.

I consider our engine (1988 Perkins 4-108) to be fairly unreliable.
Well, here are some thoughts...

I don't know what "1kw of battery capacity" is. Capacity is usually listed in Amp-hours or it could be Watt-hours. Can you please check this and give us some more information?

As already stated, you need an energy budget so we can help with specifics. I believe you will find that your heaviest electrical load will be when you are underway. This is because of loads that are only turned on underway such as nav lights, VHF, chart plotter, radar, etc. Just looking at it though, with a fridge and a freezer, it does appear that the 350 Watts of solar will not keep your batteries full and you need to have some other means of charging.

We crossed the Atlantic in 2014 and have been in the Med since. If you are coming to the Med, then you need to have your engine absolutely reliable. The winds here are fluky and you will spend more time motoring than you expect. I met one sailor in Mallorca who was on his way back to the US in September. He had just arrived in the Med that spring, but he was so frustrated with the lack of sailing conditions that he was going back after only one summer in Europe. In short, I think you need a reliable engine.

I would put a Balmar or some other brand good alternator on it with a regulator. This will be your backup for charging your batteries. I would not put on a second alternator. For your redundancy just keep your existing alternator on board as a spare. Each boat and each crossing is different, but on the northern route we enjoyed a hot shower once in a while. I do know we motored twice - 7 hours once and over 36 hours another time.

On Orontes II we have 540 Watts of Solar with our 900 Amp-hour battery bank and could sail indefinitely with that installation, given good sun. We do have a wind vane, which reduces load considerably.

I also have an installed genset, which is a third means of charging batteries. Some people have a Honda generator for this purpose. There are some real concerns with going this route (search on old posts) but it would give you another way to charge batteries.

Cheers!

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Old 20-07-2019, 15:02   #6
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Re: Electrical resiliency for Atlantic crossing

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Well, here are some thoughts...

I don't know what "1kw of battery capacity" is. Capacity is usually listed in Amp-hours or it could be Watt-hours. Can you please check this and give us some more information?
Sorry, I meant to say 1000amp/hr. To be exact, it's 985amp/hr without including the starter batteries. My mistake.

Our engine has a mount for a second alternator that was clearly utilized at some point, which is why I'm tempted by the idea. It seems like an easy modification.

Sounds like it's time for me to create a real energy budget. I've been putting it off for some time now. I have a good idea of general electrical load (both at anchor and underway, and yes it is significantly higher while on passage) but I've never actually tested or calculated the amp draw of each piece of equipment.

More solar might not be a bad option. We certainly have the space for it.
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Old 20-07-2019, 15:19   #7
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Re: Electrical resiliency for Atlantic crossing

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I don't know what "1kw of battery capacity" is. Capacity is usually listed in Amp-hours or it could be Watt-hours.
Yes, watts or kW is not storage capacity, but instantaneous flow rate.

Otherwise, simple math, A * V = W, or Ah * V = Wh

1000Ah if a 12V bank, call it 12.5V average,

so 12,500Wh or 12.5kWh

Yes Ah is a better unit, but only when the voltage is obvious and consistent.
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Old 20-07-2019, 15:21   #8
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Re: Electrical resiliency for Atlantic crossing

You're going to want redundancy for power production. On our first trip across we saw almost no sun 50% of the time, but the other half were beautiful sunny days . On the way back from the Canaries to the Caribbean, we had the mainsail shadowing the solar panels for most of the day (even the one one way out on the davits!) or gray skies. This last trip was mostly sunny, but even then, the wind gen made most of our power.

I'd suggest a little suitcase inverter generator if you're concerned with the engine's reliability. Something like a Honda 2200 or a knock off.

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Old 20-07-2019, 15:23   #9
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Re: Electrical resiliency for Atlantic crossing

How times have changed, when I started offshore sailing (btw that is over 50 years ago) we didn't have or even know what electrical resiliency was or is,

neither did we have an electric autopilot, fridge or freezer or any form of GPS, we used a sextant a watch & paper charts & Ice for cooling for the first couple of days and after that the most important non navigational item was the can opener,
having said that my latest boat has a fridge/freezer, autopilot, GPS, solar panels etc etc

Given my age I find it is very nice to take your home comforts with you!
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Old 20-07-2019, 15:26   #10
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Re: Electrical resiliency for Atlantic crossing

btw I have nearly 600 amp of battery power & 250 watts of solar, it is needed to run everything, on my sailboat!
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Old 20-07-2019, 15:27   #11
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Re: Electrical resiliency for Atlantic crossing

Well more or better alternators wonít help if the concern is the engine breaking down.
Efoy is one way, a way that I canít afford especially considering itís meager output.
Iíd say either more solar or a Honda, Iím a fan of the Honda myself, itís actually a huge amount of power, more than 2000W of solar to compare, so you donít have to run it for hours and hours, just an hour in the mornings tops to give the bank a big boost and let Solar finish it off.
In other words replace your engine time with Honda time, surely one 5 gl can would be enough too.
You may find it useful when you get there, and they are usually very easily sold too if you donít want it anymore.
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Old 20-07-2019, 15:44   #12
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Re: Electrical resiliency for Atlantic crossing

We did a to Azore passage 2 yrs ago from Connecticut. We had 285 w of sollar and 4 trogen 105's. (about 450amp/hrs). We used autopilot the whole way . We hardly used the engine at all. We have frig but no freezer. Our boat is well balanced with a skeg so the autopilot doesn't use an excessive amount of elec. We have led's in cabin, a low draw AIS(vesper) and a 7" chartplotter which we ran but didn't really "need" to. Didn't use radar. One draw was crew members charging their electronics. ipads etc. We lucked out with fairly good winds and did the trip in 15 days to Horta.

I know a boat that just also crossed to Azores and had to shut off freezer some of the time to conserve fuel for engine. I'd look at your consumption budget- esp what the freezer requires.
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Old 20-07-2019, 15:59   #13
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Re: Electrical resiliency for Atlantic crossing

“An engine with a single alternator” to me implies a standard Hitachi at 65A or so output. For 1000Ahr bank that’s pretty light. I would think a big frame alt at north of 100A would be more appropriate but that’s just me. In my experience, big frame alts do not fit well on the normal engine mount position.

Couple of things.

Losing a freezer because of failure of electrics can be a train smash especially if it happens on day 2. We had that once and threw away all of our best food in a 22 day voyage.

Losing an auto pilot is even worse. Hand steering a boat for a week is an awesome strain on crew especially if you’re short-handed and seriously to be avoided. The good news is that the average auto pilot uses minimal power and when we lost all electrical power, the last thing to stop was the AP.

If I had to rate disasters in order I would rate a total loss (sinking) as No.1 and full electrical failure as No.2. Because anything that goes wrong after No.2 compounds very rapidly. For that reason I have sound redundancy and improving it all the time. I have three alternators (65A Hitachi on engine, 150A Leece Neville and 120A Bosch both on a bracket ahead of the engine) and I carry a spare starter motor since that will be the primary cause of no engine start.

I have a 280w solar array that is presently being tripled in output with separate MPPT controllers on each sector. I have a wind generator. I have 800Ahr house bank and two 100Ahr batteries in the start bank.

A total electric failure means no engine start which means no motoring in an emergency (loss of rig for example), inability to run for cover in pending bad weather and inability to safely enter dodgy harbours/inlets. Fridges, nav equipment, auto pilot, a long list of essential (not luxury) elements disappear with no electricity - it is, to me, critically important.
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Old 20-07-2019, 16:02   #14
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Re: Electrical resiliency for Atlantic crossing

I use significantly more power while on passage. Solar is great unless the sun don't shine. A recent 1200 nm passage was tuff on batteries due to very little sun and a very dumb smart regulator. I ended up using the little Honda in the cockpit, not ideal but the weather was such that it allowed it.

If you could make your engine reliable, a good alternator and smart regulator is the easiest way to supplement the solar panels. Hydro generators are great but can be expensive and tend to be useless currently in the Atlantic due to seaweed.

Getting back to the Honda, it maybe the cheapest way (as long as you have a decent charger) to insure plenty of power while on passage, not necessarily the best way, but cheapest and easiest.
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Old 20-07-2019, 16:10   #15
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Re: Electrical resiliency for Atlantic crossing

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You're going to want redundancy for power production. On our first trip across we saw almost no sun 50% of the time,

Would that be at night?
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