From: Glenn Dennis
Subject: [Electric Boats] Re: Converting an Albin 27
To: electricboats@...
Date: Friday, November 26, 2010, 9:51 PM

?

Eric and anyone else

Still lots to think about. Now I would like to determine prop pitch and gearing. Some of the electric conversion web sites say that because of the torque produced by a electric motor you should go to a large pitched prop. The largest prop I could fit is a 13 inch dia prop, obviously the more pitch the more torque required to turn it at a given RPM and the more boat speed. Aprox boat speed can estimated by pitch x prop RPM, but how would you determine the amperage draw to achieve that RPM. Of course gearing would come into the picture but that's easy to deal with. I guess my question boils down to, is it more efficient to run a electric motor at medium or high RPM? i.e. If I want to motor at 4 knots would I gear the motor to turn at 2400 RPM (max) or at 2000 RPM. Since I would be using 4 knots as an common speed I would pitch the prop to be most efficient at that speed. Yes
this is starting to wander but both issues are connected.

And to really highlight my ignorance is the speed of AC motors regulated by voltage like DC or by amperage or both.

Glenn

--- In electricboats@..., "Eric" <ewdysar@...> wrote:
>
> Glenn,
>
> I wouldn't go smaller than a 90 or 100Ah Li battery bank, small banks have bigger issues with Peukert's Effect, they lose more power under high load rates. You could also consider 4 group 31 AGM (105Ah) to begin with, they would weigh about 280 pounds, but you should get about an 8Nm range at 4Kts to 80% DoD. Then after you win the lottery, you can upgrade to the latest Li batteries. :)
>
> If you're thinking generator, Mike has been successful with his Honda 2000 and a charger, I think that he can put about 15A into his system when the generator is running, that is about half of your 4kt load, so your batteires should last twice as long at that speed. There are some chargers available that can deliver more than 20A at 48V running on a Honda or Yamaha 2000 generator. The generator should be on deck while running. But the good part is that you don't need to set it up until you think that tyou need the range. If it's truly a day sail, you can leave the generator ashore.
>
> It sounds like your getting your head wrapped around this project. Let us know if you need more info as you do more research.
>
> Fair winds,
> Eric
> >
>

Glenn,

I wouldn't go smaller than a 90 or 100Ah Li battery bank, small banks have bigger issues with Peukert's Effect, they lose more power under high load rates. You could also consider 4 group 31 AGM (105Ah) to begin with, they would weigh about 280 pounds, but you should get about an 8Nm range at 4Kts to 80% DoD. Then after you win the lottery, you can upgrade to the latest Li batteries. :)

If you're thinking generator, Mike has been successful with his Honda 2000 and a charger, I think that he can put about 15A into his system when the generator is running, that is about half of your 4kt load, so your batteires should last twice as long at that speed. There are some chargers available that can deliver more than 20A at 48V running on a Honda or Yamaha 2000 generator. The generator should be on deck while running. But the good part is that you don't need to set it up until you think that tyou need the range. If it's truly a day sail, you can leave the generator ashore.

It sounds like your getting your head wrapped around this project. Let us know if you need more info as you do more research.

Fair winds,
Eric

Mark

What motor and controller do you have? Did you get it as a kit or build it your self? What gear ratio and prop are you running? Sorry for all the questions but I am trying to figure this out.

Glenn


--- In electricboats@..., "acsarfkram" <acsarfkram@> wrote:

Hi Glenn,

With my Ericson 27, (7000lbs before batteries) I have motored for 7 hrs at a draw of 20 amps. At that point I was using a small 2 blade prop that gave me 3 knts at that current draw. I now have a fixed 3 blade that gives me 4 knts at 20 amps.

During that trip I used only one of the two 48 volt 100 amp hr banks that I have. I do not know how deep I discharged that bank because I didn't have a monitor at that point. It was probably deeper than you should discharge but I did have power at that point.

I understand the theory dictates lower run times but I would be interested in what people are getting in real life.

Mark
Santa Cruz

--- In electricboats@..., "Eric" <ewdysar@> wrote:

Hi Glenn,

With my Ericson 27, (7000lbs before batteries) I have motored for 7 hrs at a draw of 20 amps. At that point I was using a small 2 blade prop that gave me 3 knts at that current draw. I now have a fixed 3 blade that gives me 4 knts at 20 amps.

During that trip I used only one of the two 48 volt 100 amp hr banks that I have. I do not know how deep I discharged that bank because I didn't have a monitor at that point. It was probably deeper than you should discharge but I did have power at that point.

I understand the theory dictates lower run times but I would be interested in what people are getting in real life.

Mark
Santa Cruz

--- In electricboats@..., "Eric" <ewdysar@> wrote:

These are trade size L16 batteries - often called Floor Sweeper
Batteries. IMHO, a MUCH better buy then the common Golf Cart
batteries. L16s are typically around 400Ah, but more importantly are a
bit more robust and will deliver 50% or so more cycles then the golf
cart batteries (~750 vs ~500 according to manufactures literature I have
seen).



They are around the same size, but about twice as tall as Golf Cart
batteries.



IIRC, they tend to be around 115 to 125lbs each.





-al-

Glenn,

I wouldn't go smaller than a 90 or 100Ah Li battery bank, small banks have bigger issues with Peukert's Effect, they lose more power under high load rates. You could also consider 4 group 31 AGM (105Ah) to begin with, they would weigh about 280 pounds, but you should get about an 8Nm range at 4Kts to 80% DoD. Then after you win the lottery, you can upgrade to the latest Li batteries. :)

If you're thinking generator, Mike has been successful with his Honda 2000 and a charger, I think that he can put about 15A into his system when the generator is running, that is about half of your 4kt load, so your batteires should last twice as long at that speed. There are some chargers available that can deliver more than 20A at 48V running on a Honda or Yamaha 2000 generator. The generator should be on deck while running. But the good part is that you don't need to set it up until you think that tyou need the range. If it's truly a day sail, you can leave the generator ashore.

It sounds like your getting your head wrapped around this project. Let us know if you need more info as you do more research.

Fair winds,
Eric

--- In electricboats@..., "Glenn Dennis" <vega1184@> wrote:

Eric

Thanks for the input, IMO the battery is key here.

The actual power required to push the boat and the reserve capacity was what I was unsure of. It's good to get advice from some one who has experience in the field rather than just going it alone. Truthfully I had been more interested in the mechanical part of the system and did not put much effort in calculating the battery requirements. I was a little optimistic on range but I could start with smaller pack and go larger later. L/A or AGM will certainly add a lot of weight, maybe a smaller lithium pack, say 40 or 50 Ah and generator (Hybrid) would be the way to go. Several things to consider and of course cost; the boat although in very good shape is 39 years old.

Glenn

Eric

Thanks for the input, IMO the battery is key here.

The actual power required to push the boat and the reserve capacity was what I was unsure of. It's good to get advice from some one who has experience in the field rather than just going it alone. Truthfully I had been more interested in the mechanical part of the system and did not put much effort in calculating the battery requirements. I was a little optimistic on range but I could start with smaller pack and go larger later. L/A or AGM will certainly add a lot of weight, maybe a smaller lithium pack, say 40 or 50 Ah and generator (Hybrid) would be the way to go. Several things to consider and of course cost; the boat although in very good shape is 39 years old.

Glenn

Glenn,

Good reasoning on developing your budget, but I find your orignal budget a little aggressive, you will propbably go over that number by the time you get a running conversion with basic instrumentation. You can leave some stuff off, but you'll probably end up spending the money eventually. To do the project as you describe, I would brace yourself for about $5k US. Who knows, you could even come in under that...

Looking at your design parameter, you said that your basic "stretch" requirement is 20Mn @ 4kts. I find that somewhat challenging but still reasonable. Let's do a little math.. :)

Because we don't know anything else about your system yet, we'll have to go with some broad estimates. But I will go out on a limb and state that these "guesses" will be closer than you might think.

The first assumption is that your boat will take about 1500W (2hp) to power at 4kts. You might do better, you could do worse, but this is close enough for estimating. At 4kts, you'll need 5 hours of capacity. I never estimate a battery pack at more than 80% depth of discharge (DoD), even if the battery chemistry can take it. If you think about it, when was the last time that you ran your car to 100% DoD of the gas tank? I think that we all fill up before we run completely out of fuel and typically treat our boats the same.

Speaking of battery chemistry, different types of batteries act differently in storing energy, delivering energy and their lifespan measured in charging cycles. How far you regularly discharge your batteries can affect their lifespan, but this thread is not the place for that discussion, I don't want to get sidetracked...

So for your battery types, I will use 65% DoD for flooded batteries (FLA) and 80% DoD for AGM. If you want to use different DoD, let me know and I can recalculate the numbers.

So we're aiming for 5 hrs at 1500W. Here we go....

FLA batteries like T-105s or T-125s have a Peukerts exponent of 1.25 and using a 65% DoD, you need 14kWh to give you the required 9100Wh usable to run for 5 hours. That's 290Ah of FLA batteries at 48V. US Battery makes the US305EXC 290Ah 6V battery that weighs 102 pounds; you would need 8 batteries for a combined weight of 816 pounds. These batteries seem to cost about $200 a piece or $1600 for your boat

AGM batteries have a Peukerts exponent around 1.15 and using a 80% DoD, you need 11kWh to give you the required 8800Wh usable to run for 5 hours. That's 230Ah of AGM batteries at 48V. Trojan makes the 8D-AGM 230Ah 12V battery that weighs 167 pounds; you would need 4 batteries for a combined weight of 668 pounds. These batteries appear to cost around $650 online or $2600 for your boat

Just for fun, let's look at LiFePO4 batteries, they have a Peukerts exponent around 1.05 and using a 80% DoD, you need 10kWh to give you the required 8000Wh usable to run for 5 hours. That's 200Ah of LiFePO4 batteries at 48V. Thundersky makes the TS-LYP-200AHA 200Ah 3.2V battery that weighs 16.1 pounds; you would need 16 cells for a combined weight of 260 pounds. These batteries cost $260 or $4160 for your boat. Lithium batteries should have extra protection; a battery management system (BMS) will cost approximately $500 for these batteries, pushing the cost to around $4700.

Whew, that's a lot of info, but I suggest that you mull it over for a while and see how it feels. Another answer is to change your requirements, a 15 mile range @ 4kts is obviously cheaper and lighter and so is 20Nm @ 3kts.

But I like your original request, my 30' ketch conversion with LiFePO4 batteries is spec'd to run 16Nm @ 4 kts. I should be able to verify that performance within a month or two and I'll post my results here.

Fair winds,
Eric
Marina del Rey, CA


--- In electricboats@..., "Glenn Dennis" <vega1184@> wrote:

Eric and all

I set the budget based on what it would cost me to repower with a new/old stock diesel (Volvo MD2001 9 Hp, 1 Cyl). I currently have a non-working inboard gas with feathering prop (Albin Combi drive) that is too small to work with anything else. I use a 9.9 outboard mounted on the transom, it works for the most part but if there is over 2 or 3 ft swell the prop tends to come out of the water and you can't charge the house batteries. Most of my motoring is just out and in to the Club, less than 10 min @ 3 or 4 Kts, each way most days. Top speed is not a real concern 5 or 5.5 kts would be more than enough, but would I have to have longer range for when you have to get back. I would like 20 Nm @ 4kts. I have had the boat two years now and mostly just day sail with a couple of weekend trips every now and then, but I want to do longer trips. Also I sail solo often.

With either option I will need Prop, shaft, coupling, exhaust, etc. Because of design the largest prop I could fit would be 13 inches, maybe 14 if I could get it back far enough, I was considering a 13 X 13 pitch. As for space the Vega is blessed/cursed with 23" wide X 48" long X 16" high void behind the current engine occupied by only an exhaust pipe. Also it's easy to make wider, I could fit 4 X 8d batteries no problem. Weight however would be another issue at 4 x 66 kg she may have a bow up attitude. I could try to keep them as for forward as possible may making a step cover for one. 6 volt GC batteries would be easier to distribute.

"As long as you approach this project with your eyes open to what it really means, then you shouldn't be disappointed."

That's why I'm here, trying to learn as much as possible before I comitt to the project. Oh and it would be nice to have a quiet "green" boat.


Glenn

Eric and all

I set the budget based on what it would cost me to repower with a new/old stock diesel (Volvo MD2001 9 Hp, 1 Cyl). I currently have a non-working inboard gas with feathering prop (Albin Combi drive) that is too small to work with anything else. I use a 9.9 outboard mounted on the transom, it works for the most part but if there is over 2 or 3 ft swell the prop tends to come out of the water and you can't charge the house batteries. Most of my motoring is just out and in to the Club, less than 10 min @ 3 or 4 Kts, each way most days. Top speed is not a real concern 5 or 5.5 kts would be more than enough, but would I have to have longer range for when you have to get back. I would like 20 Nm @ 4kts. I have had the boat two years now and mostly just day sail with a couple of weekend trips every now and then, but I want to do longer trips. Also I sail solo often.

With either option I will need Prop, shaft, coupling, exhaust, etc. Because of design the largest prop I could fit would be 13 inches, maybe 14 if I could get it back far enough, I was considering a 13 X 13 pitch. As for space the Vega is blessed/cursed with 23" wide X 48" long X 16" high void behind the current engine occupied by only an exhaust pipe. Also it's easy to make wider, I could fit 4 X 8d batteries no problem. Weight however would be another issue at 4 x 66 kg she may have a bow up attitude. I could try to keep them as for forward as possible may making a step cover for one. 6 volt GC batteries would be easier to distribute.

"As long as you approach this project with your eyes open to what it really means, then you shouldn't be disappointed."

That's why I'm here, trying to learn as much as possible before I comitt to the project. Oh and it would be nice to have a quiet "green" boat.


Glenn

Eric I'd look into a taffrail generator like that sold by Hamilton Ferris.?? I finally gave mine away after giving up sailing, but it would put out a pretty reliable 4-5 amps at 4-5 knots on my 26' Pearson monohull.?? It didn't weigh much and would certainly keep ahead of my electrical loads.???? I even used it when I was motoring to supplement the rather puny outboard alternator.????

Nice thing about the contraption is I could bring it aboard when I was more interested in speed than generating...?? Only problem I had with it was it seemed to have an affinity for seaweed...

Bill

Glenn,

I'm interested in your budget. How much would a diesel re-power cost for your boat? Are you considering electric primarily because you think that it is a cheaper alternative to ICE?

You should seriously think about the compromises that you're signing up for. A 500 lb flooded or AGM battery bank will drive your boat about as far as 0.75 gallons of diesel. The Vega is a small boat, do you have room for eight 6V golf cart batteries or four 4D batteries?

A new Beta twin diesel weighs about 200 pounds. A decent sized electric drive will weigh 200+ lbs more than a diesel system, including a full 8 gallon fuel tank, that is sized for your boat.

How long have you been sailing your boat? How much fuel do you usually burn over the course of your regular trip? When I realized that I rarely burned one whole gallon per trip in my boat, electric drive became more feasible. I'll spend at least 80% of what I would have spent for a diesel re-power that I did myself, so I'm not doing it to save money.

As long as you approach this project with your eyes open to what it really means, then you shouldn't be disappointed. i've seen a number of newly converted boats that obviously did not meet their owner's expectations.

Fair winds,
Eric
Marina del Rey, CA


--- In electricboats@..., "vega1184" <vega1184@> wrote:

I need to repower my 27' sailboat was looking at a diesel but electric has interested me. I have a strong mechanical background and some electrical experience mostly automotive and a little residential, that being said I can safety repair most anything; it's designing where I may need some help. I have a very healthy respect for electricity and always ensure cables are properly terminated, sealed and secured, all grounds are in place and all batteries secured.
First off budget is an issue I don't want to go over $4K, from prop to batteries, is this possible? Rough guess shaft, prop, bearings, etc $1K. Kit something like Thunderstruck, Sevcon Brushless Sailboat Kit - 8.5KW () $1.5K. Wiring, motor mount, belt drive reduction, misc bits $0.5K. That leaves $1K for batteries and chargers, not much I know, but I could add more later. I would thinks 48 volt would be better (at least safer), but amps are starting to get high. Batteries, I guess I would have to go with AGM, have some space, would love LiFePO4 but out of my buget right now. Any one have any suggestions?

Boat Specs
1971 Albin Vega
LOA 27'
LWL 23'
Beam 8' at WL 7'
Displ average 6500 Lbs

Glenn

I love it when you lay it out for us. I'd like to throw in a few points
however. The Catalina 30 actually has a shorter waterline, its listed as
25', while the Hunter 27 has a full 27' waterline and the Hunter's
displacement is listed as about 7,600 lbs, while the Catalina weighs in at
10,200. The current Hunter 27 really isn't in the same class as the older
Hunters of that length or the Catalinas. Its more of a stretched 25 footer
than a roomy cruiser.

Those other numbers won't dramatically affect what usually works out to a
lot of factors like how the boat is loaded, the condition of the batteries,
and the weather and sea conditions. I wouldn't put it past them to be
quoting range and speed that assume you're sailing down hill:)

I would assume, but take this with a grain of salt, that Hunter and Elco
would have this set up very well optimized and worked out. They've both got
extensive experience and complete control over every component so they
should be able to make a good show of things. We'll know as soon as someone
on the list buys one, any takers?

David

On Wed, Nov 24, 2010 at 3:26 PM, Eric <ewdysar@...> wrote:

David,

I ran some quick numbers to see if 20 miles at 6kts is reasonable from that
battery bank.

214Ah @ 72V = 15.4kWh
80% depth of discharge = 12.3kWh usable...

So I would believe 20nm @ 4.5kts from specific info that you posted from
Hunter. That is very good performance from an electric conversion of this size....

Of course, these are all estimates based on experience collected here and
with other electric conversions. Hunter's results may vary, the only
effective way to find out is to put one of their 27e's through its paces.
Let's hope that someone here buys one and gives a detailed performance and
efficiency report.

Fair winds,
Eric
Marina del Rey, CA