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Old 04-12-2013, 01:04 PM   #101
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You sure get around from your Friday Harbor base. I used to live over looking False Bay on SJ Island.
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Old 04-12-2013, 04:31 PM   #102
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Here is some of the weight savings when you get to choose your rpm for DC gen set vs an AC gen set at a fixed rpm. For an AC gen set to be close but still heavier than its DC counterpart, it will be screaming at 3600 rpm to produce its output. If it is a 1800 rpm AC gen set, then for the same output as these Volvo Penta DC gen sets, it will be twice the weight.

Polar DC Marine units

Ratings kW (continuous)


5.5 kW @ 2900 246 lbs
8 kW @ 2900 290 lbs
14 kW @ 2900 337 lbs
20 kW @ 2900 396 lbs

Now to power your AC loads while on the hook, it is much more efficient to run them with an inverter and enjoy the silence of a pristine anchorage and when the need arises for the batteries to be charged, you have a diesel running under a good load for a short time, then back to silence. If sized right, could power loads such as A/C and galley. Adding some solar panels would cut down the run time of the DC gen set.

When I designed off grid power for homes it was before LiFePO4 cells, so had to use lead acid batteries. A real short coming of LA batteries is the Peukert effect which basically means the higher the draw, the less total capacity. To minimize this I always used 48 VDC input inverters which for the same wattage out pulled 1/4 of the amps that it would from a 12 volt battery bank. A typical battery bank for one of these mountain off grid homes was (24) 2 volt, 700 a-hr cells. Since LiFePO4 cells only have a fraction of the Peukert effect of LA, and most the systems on a boat are 12 volt (lights, electronics, watermaker, fridge, radio), then for the trawlers that want peace and quiet in a remote anchorage, that would be the way to go. A pack 1/4 the size that Reuben is using would handle house loads for a week without solar or running the gen set. Even the smallest 5.5 kW 246 lb DC gen set would charge a 12 volt bank at 370 amps, so run time after a week of quiet bliss would only be 2 1/2 hours. Not a bad deal for being a good neighbor in an anchorage.
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Old 04-12-2013, 11:19 PM   #103
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Kite sail propulsion has been split into a new thread located here.

Kite Sail Propulsion
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Old 04-13-2013, 12:21 AM   #104
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Here is something those lithium cells can power up via an inverter......

Induction cook top for the galley.


While Reuben is away I'm going to toot his horn. His boat "Sunshine" has employed what I see is the future for cruising. Small things that you didn't know how much you would have wanted on a boat, but after using, you would never go back, induction cook top comes to mind. I've used it and will never go back because I'm lazy. A cooking surface that is flat and doesn't get hot, doesn't bake spilled food into nooks, crannies, and inaccessible areas, instead it is a single wipe across the surface and done. Here is a picture of the galley on Sunshine.
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Old 04-14-2013, 07:05 AM   #105
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induction cook top comes to mind. I've used it and will never go back because I'm lazy.

How well does an induction cook top work from a NON sine wave inverter?
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Old 04-14-2013, 11:09 AM   #106
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I don't know, never tried it. By non sine wave you mean a modified sine wave, not pure, right?
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Old 04-14-2013, 07:50 PM   #107
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We have two 3.6 kW Outback inverters. The induction cooktops work perfectly. I'd recommend these inverters over any others I've used. We now invert all our 120 VAC using shore power only for battery charging AC loads include air conditioning, hot water, TVs, Hitachi refrigerator, Bose 3.2.1.
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Old 04-14-2013, 08:03 PM   #108
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I just love hearing ".....AC loads include air conditioning, hot water," on batteries and inverter(s).

Like I said, the way of the future.
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Old 04-15-2013, 12:09 AM   #109
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A cooking surface that is flat and doesn't get hot, doesn't bake spilled food into nooks, crannies, and inaccessible areas, instead it is a single wipe across the surface and done.
What brand of Induction top do you have shown - nice job. We are considering various induction top alternatives to replace the Princess 3 burner. Right now we have portable that does OK. We took out our home gas stove and installed induction some years ago, great choice so far.
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Old 04-15-2013, 12:18 AM   #110
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For the boat I would stay with the inexpensive portable (like a hot plate) type induction cook top. They run 1500~2000 watt 120 VAC, not as powerful as the 2500~4000 watt 240 VAC built ins for the home kitchen, but the only time I use the highest setting is to quickly bring water to a boil, all cooking the lower power portable works great

I'll bet Reuben with 15 kW surge on those (2) 3.6 kW inverters is probably running home type unit in the 2500+ watt range.
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Old 04-15-2013, 08:54 AM   #111
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When we build Sunshine, we could not find a good, inexpensive induction cook top that would mount in the counter top. And, the quality home units that had more than a single burner were operating at 240 VAC (something we did not consider, though with the pair of inverters we did install, we could have easily ganged together for 240 VAC). So, we ended up with highly recommended commercial, drop-in units (120 VAC each), designed essentially for buffet, omelette stations, etc., in hotels and restaurants. Cost - $689.95 each. CookTek MCD-1800 - 1,800 watts each at full power.

Now, there is a good selection of home units that would do the same job at affordable pricing. On our smaller e-boats, we'd use inexpensive cook tops matching them with a good microwave/convection oven. On a higher-end unit, we would look closely at 240V quality home-style. I do love the CookTeks though!

Bob: I perused the kite flying thread - not sure if I'm ready for that yet! I'd go much sooner with a pair of folding masts and wind turbines! My guess is we'd get the same benefit as kites on a windy day in broad-reach cruising - straight down wind, not so much. And as I have done my share of off-shore cruising, I now prefer coastal and inland waters - can't see deploying a kite on the ICW!!!
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Old 04-16-2013, 06:22 AM   #112
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can't see deploying a kite on the ICW!!! __________________


At least the bridge tender would have a better reason to open than a boat that doesn't bother to strike a VHF antenna .
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Old 04-20-2013, 12:48 PM   #113
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Has anyone used a kite? Just how much work are they?
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Old 04-20-2013, 12:55 PM   #114
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My colleagues have on a commercial ship. Their system is a hands off, deployed and retrieved from the bridge type of system.

Since you are currently cruising the keys, isn't wi-fi nice? You can cruise and stay active on the forum. Are you cruising under electric power alone?
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Old 04-28-2013, 09:55 AM   #115
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When looking at the cost of a boat/house bank conversion to LFPs on a ROI cost comparison basis you "must" include total system impact. For example, the incredibly low resistance of the LFPs can destroy alternators, so having some means to regulate their output to control thermal shutdown or burn up must be factored into design and cost. Seems the current thought is to add a smart regulator with temperature sensor to alternator frame that gradually reduces output as temperature increases. This same issue becomes important if the BMS actuates the bank disconnect solenoid while the alternator(s) are outputting power...your diodes die. On my boat (in progress lfp conversion) this involved leaving the agm starters batteries in line as a buffer for the alternators. The use of our existing Victron inverter/chargers involved agonizing hours(read billable) of programming questions and attempts that eventually lead to a solution. In summary, this project has multi-layered costs well beyond the purchase price of the batteries and a bare BMS. These "unanticipated costs" have rendered any direct ROI benefit very upside down (not with standing indirect intangible benefits).
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Old 04-28-2013, 11:22 AM   #116
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When looking at the cost of a boat/house bank conversion to LFPs on a ROI cost comparison basis you "must" include total system impact. For example, the incredibly low resistance of the LFPs can destroy alternators, so having some means to regulate their output to control thermal shutdown or burn up must be factored into design and cost. Seems the current thought is to add a smart regulator with temperature sensor to alternator frame that gradually reduces output as temperature increases. This same issue becomes important if the BMS actuates the bank disconnect solenoid while the alternator(s) are outputting power...your diodes die. On my boat (in progress lfp conversion) this involved leaving the agm starters batteries in line as a buffer for the alternators. The use of our existing Victron inverter/chargers involved agonizing hours(read billable) of programming questions and attempts that eventually lead to a solution. In summary, this project has multi-layered costs well beyond the purchase price of the batteries and a bare BMS. These "unanticipated costs" have rendered any direct ROI benefit very upside down (not with standing indirect intangible benefits).
I was able to address these issues with minimal cost, but countless hours of effort researching and implementing my install. But outside of the BMS and the cells, I was able to make it all work without additional system modifications. I do need to spend a couple hundred on an upgrade to my Magnum I/C firmware and controller to simplify the operation. I use the same solution for alternator diode protection.

And if you are paying hourly rates for the conversion, it will be hard to quantify the time/cost required. There just aren't many marine electricians out there familiar with the technology.

But the biggest barrier to ROI analysis is cycle life. At this point we only have a few data points, mostly from lab testing and a little from the EV community. Neither match our operating profiles in a real life system. Further there are open questions on "calendar" life, especially for occasional use.

I believe we will find cycle life in the 2X to 6X what we see with FLA/AGM. And calendar life somewhere between 6-12 years. But these unknowns make analysis only a best guess, no matter what values used in the analysis.

Then there are hard to quantify benefits like I think I am running my generator fewer hours. I have enough data now, need to see if I can boil it down and quantify that a bit more. Both my inverters and my DC water maker especially are happier with the extra 1/2 volt. Will that lead to longer life? Who knows. The water maker does make 5-10% more water per hour.

You have to like tinkering with new technology right now. I'm working on a better BMS for Marine derived from Industrial Automation components. In part since I'm not happy with my BMS flexibility, and a hope to have an application to simplify the installation equation for others. But it remains to be seen how well it will work when complete.

Anyone who claims a big ROI right now, ask for proof not promises. The potential does exist, but it's not proven. The exception is those with size/weight restrictions that can't be met otherwise.
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Old 04-28-2013, 12:06 PM   #117
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Some really good info from the above posters, thanks guys.
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Old 04-28-2013, 02:55 PM   #118
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A review of records for generator runtime shows:

From our trip departure from St Pete FL on 4/2/2011 to our LFP install in Grenada on 7/10/2012, we spent 295 nights at anchor, 1533 hours of generator time and averaged 5.2 hours of generator runtime per day.

We normally do 2 cycles per day, morning and night, consume 150Ah - 300Ah each cycle. My best over all guess is 500 Ah average daily, but it's not logged anywhere. The morning charge at 11-12AM has more to recover than the 7-8PM evening one. Primarily this runs 4 refrigeration systems and the DC water maker a couple times a week.

The 12 Trojan golf carts were still functional, but well below their original 1350 Ah rated capacity, maybe good for half of that at replacement. I think the engine room temps in the tropics may have accelerated their demise.

From the LFP install to today, we spent 127 nights at anchor, had 607 hours of generator time and averaged 4.8 hours of generator time per day.

We did not count days underway >3 hours of engine time, or days with shore power.

So...it looks like we can at least on a preliminary basis claim .4 hours a day less generator with the same loads. That's maybe $2 per day savings in fuel and maintenance? $400 a year. Not a big number, but not trivial either.

Overall in both cases the numbers were a bit higher than I expected since 4 hours per day of charging should have kept up with a 150Ah charge rate. But we must also run the generator to cook, maybe that counts for some. We do find "cooking" is the reason to hold off genset shutdown a bit more frequently than before.

Also not factored in is toward the end of life on the Trojans, we only ran the ice maker once a week and kept the supply in the chest freezer to reduce consumption. We also did not do a good job of restoring full charge to the FLA once a week or so while at anchor for extended periods. Both of these items would increase the generator time for FLA.

YMMV....
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Old 04-28-2013, 03:43 PM   #119
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Ebaugh

In the PNW we average very close to 4 engine hours per generator hour with genset currently at 410 and engines at 1750 hours. Without AC needs our situation is very different. Maybe your lavish boating E needs lifestyle is unusual, or you should do more swimming to cool off. How do sail boaters without AC manage in your cruising grounds?

Do you have high capacity engine alternators?
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Old 04-28-2013, 04:14 PM   #120
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Ebaugh

In the PNW we average very close to 4 engine hours per generator hour with genset currently at 410 and engines at 1750 hours. Without AC needs our situation is very different. Maybe your lavish boating E needs lifestyle is unusual, or you should do more swimming to cool off. How do sail boaters without AC manage in your cruising grounds?

Do you have high capacity engine alternators?
It's hard to compare I think? We live aboard 365 days a year, off grid at anchor more than 50% of our nights. We used to run the AC about an hour or two a day at anchor during the evening, but for the last year its only normally run when at dock with shore power. At anchor with the trades, almost everyone does without A/C until you get to large crewed boats. True cruising trawlers are very rare compared to sailors. At least 50, maybe 100 sailboats for every trawler.

Refrigeration power is much less efficient due to much higher ambient air or seawater temperature.

We tend to spend several days at each stop, and the distances between stops are much greater. Our last "run" was 415 NM from San Andres Island to Roatan Honduras. This is a bit unusual, in fact it's the longest single leg of our trip. But overall, legs are much longer than we had on the West Coast of Florida. As a result of the longer legs and the consecutive days at anchor, I don't think we would save much with big alternators. Ours are only 90A each, but we run them much lower than that.

The answer here is solar and wind, most every sailboat has one or the other and quite a few have both. I would add solar the next time around if at all possible.
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