Using the TT35 as a solar-electric trawler

[Scott Harris]

Like many before me, (including several who have posted on this forum), I'm afflicted with the passion to create a solar-electric trawler. I can't help it, I'm a solar nut: electric car, solar house, builds LFP battery systems for neighbors and relatives, need I say more.

I know, I know... I've run the numbers; when building true solar-electric boats (no hybrids) the force is not with you. Solar electric is not the future of pleasure boating, it doesn't make sense, it is something you have to really want to do. That being said, I think it is possible to build a workable boat and use it to cruise from Seattle to Juneau.

Three years ago I was searching for the right boat to base my project on. When I first saw a picture of Great Harbor's TT35, I knew I had found the right platform; a large flat roof for solar panels and a long, narrow, light weight boat for efficiency. So I began doing the calculations.

By ditching the AC (I'm cruising to Alaska after all),and moving the electronics to a mast up front it is possible to build a rack that holds 12 full size (60-cell) solar panels with an overhang of just 4 inches on the sides. At the time (3 years ago) this would yield 4200 Watts of solar, but now, using Sun Power's 440 watt panels you could get 5280 watts.

5280 watts is a big array, and in Florida where the solar insolation values are 5-6 you could expect to average about 30KWh per day. But in Alaska, where the insolation values are less than 2, and where it can rain 3 weeks straight in the summer, it is best to plan for very little solar contribution (although I am going to build the panel frame and populate with the highest efficiency panels anyway, who knows, someday I may transport the TT35 to FL and do the Grand Loop.)

So my boat will be more of an electric boat than a solar boat, sucking up shore power wherever it can.

My goal is to build a boat with a range of 120 miles at 7kts. This is the minimum range required to join the slow boat flotilla that cruises from Seattle to Juneau each year (slowboat.com).

Last June I corresponded with Ken Fickett who was kind enough to help me with the calculations. It seems when he announced the boat in 2016 that a couple of electric motor companies contacted him about the possibilities of creating a solar eclectic boat and they created a spread sheet modeling what could be expected. Ken shared this spreadsheet with me and it showed you could expect 7kts with 7000 watts of power. That is 1 nautical mile for1 kilowatt. Pretty handy huh? Maybe the force (EMF) is with the project after all.

This means I need two 60KWh batteries, one for each outboard on the TT35. I have designed a battery consisting of four parallel stings of sixteen 280AHr cells. Each string is protected by an Orion BMS and connected by a Blue Seas contactor to a common DC bus. When delivering 7000 watts to the motor, each string will be discharging at rate of 0.125C. Each string is designed and wired to run the full 7000 watt load by itself, so even in the WCS, if 3 strings dropped out, the last string standing would be able to safely handle the load, (although I surely would have switched to the other battery and motor by then). I have ordered the cells for the first string and hope to get them in a few weeks.

OK, here is where all the old sea salts on this forum can help. I may know a bit about solar and building LiFePO4 batteries, but I am a complete novice when it come to boats and boating. Except for a sea kayak, which I used often when I lived in Seattle, I have never owned a boat. So now I am trying to design the charging system with no experience with shore charging.

Here are my questions. Please Help.

1. Are marinas more likely to have 30 amp service or 50 amp service?

2. When using 30 amp service, is it ever possible to use two 30 amp receptacles (and pay double of course) or are the slips usually so full that this would be unlikely?

3. Is the 50 amp service always 240 volts or are there still some docks with 50 amp 120 volt service? (I am hoping for 240 volt service because I am planning to split the phase and charge both batteries simultaneously with 50 amp 120 volts)

Thanks for your input.

Scott

 

[StarChaser]

Scott,



Welcome aboard! May the EMF be with us.



I have a '82 Carver 3607 with contingency plans of making a Hybrid out of her if either of my diesels are FUBAR.



Most marinas will have 30A hookups and may or may not have 50A.



Using 2 30A hookups is more $$ but won't get you anymore power. Get the 50A, it's 240 and you use a 'Y' cable to split it into 2 30A services.



I've never run into a 12V 50A service. 240V 50A is common.



I'd be very careful with the LiFePO4 batteries. I don't think they're approved in the ABCY standards. (NiMH are, but not as efficient) If they aren't, then you may have problems getting insurance. Most marinas (East Coast) require you to have insurance in order to tie up.





Good Luck, StarChaser

 

[Scott Harris]

Hi Star Chaser. Thanks for the help.

one question

Using 2 30A hookups is more $$ but won't get you anymore power.

I don't understand this? wouldn't each line provide 120 volts at 30 amps?

I'd be very careful with the LiFePO4 batteries. I don't think they're approved in the ABCY standards. (NiMH are, but not as efficient) If they aren't, then you may have problems getting insurance. Most marinas (East Coast) require you to have insurance in order to tie up.

Excellent advice. I will look into this.

 

[StarChaser]

Scott,



30A @ 120V in a single hookup vs 50A @ 240. RMS actually gives you more usable power with 240V. You get charged for 2 30A hookups which will cost more$ per Amp.



Before committing to your conversion I would bite the bullet and obtain a copy of the ABCY standards. You may find that a lot of your questions are addressed in them and may save you some headaches from having to redo your work.



Star

 

[twistedtree]

I don't think they're approved in the ABCY standards. (NiMH are, but not as efficient) If they aren't, then you may have problems getting insurance. Most marinas (East Coast) require you to have insurance in order to tie up.

ABYC doesn't distinguish between different chemistries. The standards all presume lead acid, but a Technical Report TE-13 has recently been published for "high capacity" batteries which include Lithium Ion variants, and I don't see any reason why it wouldn't be applicable to NiMH as well. But again, it's silent on specific chemistries, neither approving or disapproving of any in particular.


Also, I've never seen an insurance policy that says you batteries need to be ABYC compliant. Maybe someone can tell us about one that does.


As for shore power, there are two types that are common, and one that is uncommon. The common ones are:


- 30A, 120V


- 50A, 120/240V split phase.


And the uncommon one is 50A 120V.


I think you should provide for use of both 30A 120 and 50A 120/240V, though of course the 50A will provide significantly more power, when available. If you come across 50A 120V, you could carry an adapter cord and treat it like 30A 120V.


The battery bank your describe 280Ah cells, 4P16S would be about 55kwh, right? Or am I having a math-moment? So you need double that, and then are still shy on the 120kwh you need for a 120nm range. And that's under perfect conditions, using 100% of the bank capacity, and no power left over for house use. Bottom line is I think you will need more capacity, or perhaps better, just dial back to 6kts.


And are there really docks with power every 120nm through northern BC? Shearwater comes to mind, but I think that's it until you get to Prince Rupert. Maybe Ocean Falls, but I can't recall if they have power.


All that said, it sounds like a cool project and that you understand what to expect, and what not to expect. "Because it will be fun to do" is all the reason anyone needs, in my book. And it's refreshing to see someone doing this knowing it's not going to do magical things.

 

[twistedtree]

Oh, ABYC also has E-30 which covers electric propulsion, and addresses some of the high voltage considerations.

 

[Scott Harris]

Thanks, all good info.

I just signed up with ABYC so that I can read E30. I'm waiting for validation now.

The nominal energy capacity of my batteries is 4x48x280 = 53,760 KWh. But 48 LIF batteries discharged at 0.1 C operate just above 52 volts for almost the entire range. So the actual energy capacity is 4x52x280=58,240. Still a little short, but all of the capacities of the cells are above 280Ah so I call it 60KWh for short.

These are traction batteries. The house batteries are separate. I will also build a 30KWh house bank. The solar panels will charge the house bank. The traction batteries cannot charge the house batteries, (I have heard that this is against AYBC code, will find out once my ABYC registration is complete) but I will be able to transfer a little energy from the house battery to the traction battery that is not being used for power while under way.

There are two sections of the Alaska trip that are challenging distance-wise. One is Port Hardy to Shearwater which is about 117 miles. However there is a fishing resort at Duncanby Landing about half way that has 30 amp power. I think that if I make prior arrangements I might be able to get power there. Ocean Falls also has 20 amp and 30 amp power. It is a bit out of the way, but would still work.

Has anyone ever stopped at Duncanby Landing? Are they nice people?

The other tight section is Shearwater to Hartly Bay. 103 miles. Klemtu is about midway but I haven't been able to find out if they can provide power.

 

[Scott Harris]

and addresses some of the high voltage considerations.

The highest voltage I am comfortable with is 48 volts. That can still be dangerous and must be respected, but it is not insane like some of the 380-400 volt motors and batteries being sold for boats.

 

[boatpoker]

Using 2 30A hookups is more $$ but won't get you anymore power.



I'd be very careful with the LiFePO4 batteries. I don't think they're approved in the ABCY standards. (NiMH are, but not as efficient) If they aren't, then you may have problems getting insurance.

I use two 30amp cords and get 30amps at each panel for a total of 60amps.

ABYC -10 does not even mention LiFePO4 or NiMH,

 

[twistedtree]

ABYC -10 does not even mention LiFePO4 or NiMH,

You need to check out TE-13 which is brand new and covers the likes of LFP, etc., though it doesn't name chemistries. It's a Technical Report, not a standard, but will eventually mature into a standard.

 

[twistedtree]

The nominal energy capacity of my batteries is 4x48x280 = 53,760 KWh. But 48 LIF batteries discharged at 0.1 C operate just above 52 volts for almost the entire range. So the actual energy capacity is 4x52x280=58,240. Still a little short, but all of the capacities of the cells are above 280Ah so I call it 60KWh for short.

These are traction batteries. The house batteries are separate. I will also build a 30KWh house bank. The solar panels will charge the house bank. The traction batteries cannot charge the house batteries, (I have heard that this is against AYBC code, will find out once my ABYC registration is complete) but I will be able to transfer a little energy from the house battery to the traction battery that is not being used for power while under way.

"LIF"? I'm not familiar with that acronym. And you say "traction" batteries which typically means big lead acid batteries, but maybe not in this context? So I guess I'm confused what battery chemistry you are planning.

 

[Scott Harris]

The chemistry I am using is lithium iron phosphate. It is abbreviated both as LiFePO4 and LIF. I use both abbreviations, sorry to confuse you.

LiFePO4 is much safer than many Lithium chemistries. If you puncture it, short it, or over charge it, it will not explode and catch fire. (see attached video, I like the part when they shoot the cell with a pistol). Still, I will have redundant disconnect systems and a thermistor on each cell.

Traction batteries are batteries used to power the motor of a vehicle, as opposed to house batteries that power everything else. The traction battery systems are bigger than the house system but are actually much simpler. The traction batteries have only one load and one supply and they are never used at the same time. That enables me to use a common port system rather than a more complicated separate port system as will be used on the house batteries.

 

[Portage_Bay]

You've set yourself on a challenging path. You'll be pushing the boundaries to run Seattle to Juneau on solar charging.

You've addressed the longer distances you'll need to cover between charging opportunities. I suggest you put effort into studying current direction and speed. Running with the current will greatly increase your range.

I'd also reach out to the marina operators at your planned stops. Seek their encouragement and support for your ground breaking voyage. Pulling in with your massive battery banks nearly depleted you will be drawing far more power than they expect to provide the typical cruising boat. Most if not all the stops you are planning don't meter their electricity. The cost of the power you will need will probably exceed what they are charging for moorage.

 

[Scott Harris]

I'm very familiar with the advantages of going with the current. When I did a lot of kayaking in the Puget and Desolation sounds, I learned that currents were strong enough to double the speed of a kayak or stop it cold. A very experienced kayaker taught me to stay in the center of the channel when the currents are with you and move to the edge (to pick up an eddy current) when they are not. That way mother nature is always helping you.

So I am wondering, since the TT35 has a draft of only 18", is that still a wise thing to do, or is that unsafe in a big boat?

 

[twistedtree]

My batteries are lithium iron phosphate. Sometimes abbreviated as LiFePO4 or sometimes LIF.

Traction batteries are batteries used to propel a vehicle; as opposed to house batteries which power everything else.

Got it. I see LFP more commonly used to indicate LiFePO4, but not a problem. And I get that you are using "traction" just to describe the purpose of the bank.

 

[twistedtree]

Recharge times will be a challenge when you only have 30A available. That's 3600W, so 34hrs to recharge your 120kwh propulsion bank. And there is another thread running currently about overloading shore power connections, and the virtues of limiting continuous power draw to 80% of capacity. Plus you will have a house bank to recharge, water to heat, and life to live, all of which will consume some of that power. It should work out OK with 50A (12kw), but with 30A you will need to plan on a few day stop.


I get the milestone of making it to AK and back, but operation of such a boat is much more suited to marina hopping around Puget Sound. But that's probably your longer term use, right?


Changing topics a bit, what are your plans for the propulsion machinery? There is another guy here who is converting a sailboat hull over to electric, and plans to use salvaged Prius parts.


And another one... what's the backup plan when the weather turns and suddenly you can't make it to the next power plug? It doesn't take much wind or seas to significantly change the theoretical power consumption numbers. Personally I'd be much more comfortable planning on destinations that are no more than 1/2 of my theoretical range.

 

[nwboater]

Like many before me, (including several who have posted on this forum), I'm afflicted with the passion to create a solar-electric trawler. I can't help it, I'm a solar nut: electric car, solar house, builds LFP battery systems for neighbors and relatives, need I say more.

I know, I know... I've run the numbers; when building true solar-electric boats (no hybrids) the force is not with you. Solar electric is not the future of pleasure boating, it doesn't make sense, it is something you have to really want to do. That being said, I think it is possible to build a workable boat and use it to cruise from Seattle to Juneau.

Three years ago I was searching for the right boat to base my project on. When I first saw a picture of Great Harbor's TT35, I knew I had found the right platform; a large flat roof for solar panels and a long, narrow, light weight boat for efficiency. So I began doing the calculations.

By ditching the AC (I'm cruising to Alaska after all),and moving the electronics to a mast up front it is possible to build a rack that holds 12 full size (60-cell) solar panels with an overhang of just 4 inches on the sides. At the time (3 years ago) this would yield 4200 Watts of solar, but now, using Sun Power's 440 watt panels you could get 5280 watts.

5280 watts is a big array, and in Florida where the solar insolation values are 5-6 you could expect to average about 30KWh per day. But in Alaska, where the insolation values are less than 2, and where it can rain 3 weeks straight in the summer, it is best to plan for very little solar contribution (although I am going to build the panel frame and populate with the highest efficiency panels anyway, who knows, someday I may transport the TT35 to FL and do the Grand Loop.)

So my boat will be more of an electric boat than a solar boat, sucking up shore power wherever it can.

My goal is to build a boat with a range of 120 miles at 7kts. This is the minimum range required to join the slow boat flotilla that cruises from Seattle to Juneau each year (slowboat.com).

Last June I corresponded with Ken Fickett who was kind enough to help me with the calculations. It seems when he announced the boat in 2016 that a couple of electric motor companies contacted him about the possibilities of creating a solar eclectic boat and they created a spread sheet modeling what could be expected. Ken shared this spreadsheet with me and it showed you could expect 7kts with 7000 watts of power. That is 1 nautical mile for1 kilowatt. Pretty handy huh? Maybe the force (EMF) is with the project after all.

This means I need two 60KWh batteries, one for each outboard on the TT35. I have designed a battery consisting of four parallel stings of sixteen 280AHr cells. Each string is protected by an Orion BMS and connected by a Blue Seas contactor to a common DC bus. When delivering 7000 watts to the motor, each string will be discharging at rate of 0.125C. Each string is designed and wired to run the full 7000 watt load by itself, so even in the WCS, if 3 strings dropped out, the last string standing would be able to safely handle the load, (although I surely would have switched to the other battery and motor by then). I have ordered the cells for the first string and hope to get them in a few weeks.

OK, here is where all the old sea salts on this forum can help. I may know a bit about solar and building LiFePO4 batteries, but I am a complete novice when it come to boats and boating. Except for a sea kayak, which I used often when I lived in Seattle, I have never owned a boat. So now I am trying to design the charging system with no experience with shore charging.

Here are my questions. Please Help.

1. Are marinas more likely to have 30 amp service or 50 amp service?

2. When using 30 amp service, is it ever possible to use two 30 amp receptacles (and pay double of course) or are the slips usually so full that this would be unlikely?

3. Is the 50 amp service always 240 volts or are there still some docks with 50 amp 120 volt service? (I am hoping for 240 volt service because I am planning to split the phase and charge both batteries simultaneously with 50 amp 120 volts)

Thanks for your input.

Scott

All very interesting and doable. Keep in mind that many “stops” along the way, particularly north of Port Hardy, may only have 20 amp power available at the dock and likely produced by a generator. Also, many facilities only run their generators for a few hours each day...or not at all!

I’m sure you’re thinking about contingent “get home” power...in which case the TT35 is ideal, set up with outboards. Look forward to following this adventure!

 

[Fletcher500]

I don't know enough about Solar to offer any help, so I will follow along. Keep us posted. Sounds like a cool project.

 

[Xsbank]

You will still need a genset or you may find yourself attached to a dock for a week. Your requirements will prohibit anchoring out. 103/7= about 14 hours of running from one spot to the next; I don't know about you but that's way past my capacity to endure day after day with days spent tied up waiting for a charge.

What's the point?

ABYC has no enforcement mechanism nor does it have the power of legislation. It may be a compendium of " best" practices but it can't deal with innovation. It is not the final arbitrator.

The coast is not amenable for solar. On a sunny day, my panels put out their rated power but they are horizontally mounted so you automatically lose a percentage of their potential. Then the wildfire smoke or simple clouds cut that back dramatically. On a sunny day I am "floating" my battery bank by 13:00, on a smoky day I need to run the genset.

I think you will find that some places will not want to run their 15 or 30 amp generators for days at a time to charge you up. Which is another consideration, how long will it take to charge your large bank with 30 amp power? It's the same problem with the current crop of electric cars, getting them charged so you can actually use them.

"Solar power and electric cars don't run on the sun, they run on subsidies."

 

[Scott Harris]

It should work out OK with 50A (12kw), but with 30A you will need to plan on a few day stop.

My hope was to use two 30 amp plugs when a marina has only 30 amp power. That is 7.2Kw of power which would recharge the traction bank in 120/7.2 = 16.6 hours. I am thinking more like 22 hours given efficiency loss and derating.

However, this time is for pulling up to the dock with completely empty batteries which would not be a safe cruising plan. If I can get power at Duncanby landing (likely) and Klemtu (unsure), then my longest leg is 98 miles (Kake to Juneau) and the average leg is 71 miles. A 71 mile refill would be about 20 hours for one 30 amp plug, 10 hours for two 30 amp plugs, and 5 hours for one 50 amp plug, plus maybe 25% for efficiency loss (my chargers are 94% efficient) and derating.

So at docks with 30 amp service only (about 40% of them), I would have to stay two nights (yuck) if I can get only one plug, and just overnight if I can get two plugs.

So the important question is, how likely is it that I can snag two 30 amp plugs at the dock. Please let me know your experience since I have never docked a boat.

 

[Scott Harris]

Keep in mind that many “stops” along the way, particularly north of Port Hardy, may only have 20 amp power available at the dock and likely produced by a generator. Also, many facilities only run their generators for a few hours each day...or not at all!

I didn't think about that. I will have to do some more research into the docks along the route. Maybe make some calls and see if I can arrange for paying for more power than they are used to providing.

Thanks for the head's up

 

[Scott Harris]

what are your plans for the propulsion machinery? There is another guy here who is converting a sailboat hull over to electric, and plans to use salvaged Prius parts.

My plan is to use two Torqeedo 10.0 R outboards that replace the gas outboards on the TT35. I am hoping to bring the first traction battery to Mirage Manufacturing this spring to do a test to see if 7kts at 7000 watts output on one motor is achievable.

Car motors run at 380-420 volts. Anything above 48 volts on a boat is way too much excitement for me. I wish that brave sole luck though.

 

[Scott Harris]

You will still need a genset or you may find yourself attached to a dock for a week. Your requirements will prohibit anchoring out

I don't understand why I would not be able to anchor out. If my average run between marinas with electricity is 71 miles, I don't see why I could not take 3 or 4 days to do that. My house bank will be 30KWh. Would that not last 3 or 4 days? (Remember, it is a small boat with no air conditioner). Also, it will have a 5,000 watt solar array. If the sun shines, that is a 10-15KWh refill everyday. So the number of times I can anchor out will be extended on sunny days.

 

[DavidM]

"Please let me know your experience since I have never docked a boat."

Hmmm. And you are going to convert a $250,000 hull to solar power???? I think you need to team up with someone who knows something about cruising boats. This forum is great for blue sky dreaming, but you need someone with practical, real world experience on your team.

David

 

[Scott Harris]

"Please let me know your experience since I have never docked a boat."

Hmmm. And you are going to convert a $250,000 hull to solar power???? I think you need to team up with someone who knows something about cruising boats. This forum is great for blue sky dreaming, but you need someone with practical, real world experience on your team.

David

Yes good advice for sure. But all projects start with blue sky dreaming and that is the stage I am in now. However, soon I will be building the first traction battery, the cells will arrive later this month.

 

[Nomad Willy]

First you’ll need a full displacement hulled vessel. No other hull is suitable. Unless you want to show that old trawlers could do it. Sure but you could do that in Lake Washington in Seattle.

Another thing that would be nice for you to have under your belt is a few trips by slow boat to Juneau. With our 6 knot boat it takes about 22 days running probably a little under 10hrs a day. I’m trying to impress upon you how far it is. Kayakers know and those that row boats to Alaska know. You don’t. And it may be a nasty run all the way or calm seas and a bit of fog.

But there’s lots of people that run sailboats north. Usually cold and rain gear clad unhappy people. But one thing’s for sure .. the other guy mentioned with a sailboat is way ahead of you. First and obvious is fuel (or electron) consumption. Sailboats are even more fuel efficient that full displacement rec trawlers.

But it seems you’re just doing this as a lark so I’ll say “may the best adventure be had”. And keep us in the loop as we’re down on interesting threads.

 

[BandB]

Scott

Have you actually purchased this boat? Is it in Alaska?

 

[Scott Harris]

Doing it on a lark? Well maybe. (Have you been talking to my wife?) But I am not a reckless person. I would never attempt to make the trip alone.

There is an organization named slow boat (slowboat.com) which guides a flotilla of five boats from Roche Harbor to Juneau or Sitka each year. They usually take about 30-32 days and do a lot of anchoring and sightseeing along the way. My plan is to qualify to go with such a group.

I reached out to one of the leaders of the slow boat group earlier this year. At first he was quite excited about the project (I think he is an electrical engineer), but I sensed the excitement waned as he calculated how difficult it would be to pull off such a project. However, I think it is doable and I am going to try.

Do I own a boat? Read the first entry and you will see that the only boat I have ever owned is a sea kayak. But I used it well; including a 5 day 175 mile solo trip from WA to Canada. Ironically this is further than any of my friends with sailboats and motor yachts had ever ventured and I loved teasing them about it. I sense that you guys are much, much more adventurous than my friends. Maybe even some circumnavigators.

So no, I don't own a boat. I have a lot to learn and that is why I joined this forum.

My first milepost does not require me to own a boat. The goal is to build the first 60KWh battery, acquire the Torqeedo motor and take them to Gainesville FL, to test on one of Mirage manufacturing's TT35 boats. I need 7kts at 7000 watts. If I can achieve that I will plan for milepost two.

 

[Scott Harris]

First you’ll need a full displacement hulled vessel. No other hull is suitable.

\\

I think that the TT35 is a planing hull. It moves pretty fast when using twin gas outboards. Of course I would be going only at displacement speeds. I'm not sure what problems not having a displacement hull would cause me. But if I can reach 7kts with 7000 watts of power I will be happy.

 

[Nomad Willy]

Scott,
Like your post.
Gain from a FD hull? Just less power required. 35’ sailboats have 15 to 30hp. Trawlers have far more. But they go faster too. You should probably shoot for 6 to 6.5 knots. But a sailboat may not work w the cruising groups you mentioned above as they will want to go faster.

An inboard electric motor would be far more preferable than the OB. And a sailboat low on draft like as swing-keel (I think that’s what they are called) would reduce draft. When the weather gets nasty you’ll want (rightfully so) you would run for the nearest anchorage. It may be very shallow and it may be very deep.

I don’t like them but a catamaran may be the best for low power consumption but you’d need two drive motors. Also a long anchor line would be a good safety feature. About 500’.