48-volt house bank. Next Gen for boats?

[mvweebles]

Impressive!!!! I extracted the schematic at the end of your article as eye candy. Having done a similar schematic for Weebles (sans 48v), I have an inkling of the amount of time, research, and effort there is to create this. Bravo!

I wish I were younger. Future looks super cool.....

Peter

 

[Jeff F]

Yep. Interesting. 17 kwh per day from solar, you reckon?

I've been playing with the idea of a 48v saildrive that would be used for getting to safety in case of propulsion failure. But I'd keep it well exercised by using it when underway to take advantage of excess solar power. A poor person's hybrid.

That's really what got me thinking about 48v.

Mcarthur, where is your boat these days? Did you buy in the Caribbean and get to the Med? I remember early discussions then kind of lost track.

 

[mcarthur]

Hi Jeff,
Yes, we bought in the Caribbean. Shipped to UK after we got a great quote compared to other methods. Was getting her ready for the French canals and Med (and even the European Loop!)... then covid locked us out. After a time it became clear that Australia was shutting doors for some time, so we investigated options to get her closer without us (you couldn't leave Oz at that time ), and ended up shipping on a RORO almost to the door.

So we're in Australia at the moment while I finish working to pay for the changes (and other things ).

re: solar, we've got 9sqm on the current cabin top, which will do about 2kW. The new solid top on the flybridge will hold another 3-4kW. Extending that over the rear deck will add another 1.5-2kW. Where we are now we get about a 4-4.2x daily kW multiplier, and in the lovely tropics it'll go up to 4.5 or so. So about 7kW of panels should give between 28-32kW/day. At an estimated 8kW propulsion from battery for 5kn of speed, that's a (sunny!) day's travel of 15-18nm on pure solar with some left for the house. Go to 4.6kn and it's 5kW for 23nm.

There's no benefit for all of this solar unless you are an energy profligate of the first degree, or using some of it for propulsion (our intent). Otherwise you'd probably stop at 2-4kW of panels.

 

[mcarthur]

Impressive!!!! I extracted the schematic at the end of your article as eye candy. Having done a similar schematic for Weebles (sans 48v), I have an inkling of the amount of time, research, and effort there is to create this. Bravo!

I wish I were younger. Future looks super cool.....

Peter
View attachment 135377

Thanks Peter. We have been watching your changes with lots of interest and learnt from your changes and posts about it - thank you.

I'm updating the schematic a bit as I've learnt more and a few things have changed. For example, my fusing was way off . I can have a single negative DC bus combining the 12V and 48V negative buses. Also I think I can get away with a couple of smaller and simpler one-way 48-12 DC buck converters rather than the bidirectional Calex 3000's. etc.

Actually the electrics are the easier bit - I'm not mechanical, and the parallel hybrid on the engine itself has languished as I need a "mate" to largely do it ... anyone happen know a good thinking mechanic in southern NSW?

 

[Jeff F]

re: solar, we've got 9sqm on the current cabin top, which will do about 2kW. The new solid top on the flybridge will hold another 3-4kW. Extending that over the rear deck will add another 1.5-2kW. Where we are now we get about a 4-4.2x daily kW multiplier, and in the lovely tropics it'll go up to 4.5 or so. So about 7kW of panels should give between 28-32kW/day. At an estimated 8kW propulsion from battery for 5kn of speed, that's a (sunny!) day's travel of 15-18nm on pure solar with some left for the house. Go to 4.6kn and it's 5kW for 23nm.

Thanks for that, and it's nice to get caught up. We've been living through strange times.

I have quite a bit of real estate available. Figure I could run primarily on diesel but blend in excess solar through a saildrive to reduce consumption/increase mpg.

So for me 48v would be to facilitate big solar and propulsion, and probably an inverter. Interesting to contemplate.

I seem to be at about a 3.5 - 4.0 daily multiplier midsummer Great Lakes. No tropical aspirations. So it's a tougher case.

 

[Jeff F]

Looking at 48v at https://www.currentconnected.com as recommended by CMS.

25 kw pack with BMS, inverter and MPPT for $9,500. Built with SOC drop ins. Hard to find fault at first glance.

 

[rslifkin]

I seem to be at about a 3.5 - 4.0 daily multiplier midsummer Great Lakes. No tropical aspirations. So it's a tougher case.

That agrees with what I've found as well. Typically we're in that range in decent weather, although in mid summer we have gotten up towards a 4.5x multiplier a couple of times on really clear days with no stuff near the boat to cause shading early or late in the day. Ours varies a little more than some, as our panels are angled slightly forward and outward on the boat due to the mounting surface. So solar production is slightly better with the boat facing south than any other direction.

 

[socalrider]

Looking at 48v at https://www.currentconnected.com as recommended by CMS.

25 kw pack with BMS, inverter and MPPT for $9,500. Built with SOC drop ins. Hard to find fault at first glance.

Very good price but I'm not sure how those server rack batteries would hold up in a marine environment.

 

[Jeff F]

Very good price but I'm not sure how those server rack batteries would hold up in a marine environment.

See my earlier thread. Batteries are replaceable at current price of $1,600 each. Durability is the least of my concerns.

Not sure about the $1,000 device that holds it all together though.

 

[Jeff F]

So here's my hypothetical 48v setup.

25 kwh 48v pack. $10k
10 kw saildrive. $10k
10 kw solar. $10k

Ship systems remain unchanged. I choose to run AC from 48v rather than 12v inverter.

Benefits:
1) minimum 2.5 hour electric only at full power, for me 6+ knots.
2) under diesel power can reduce throttle and blend in excess 48v by running saildrive at partial power. Typical cruise for me is 7.5 knots. I suppose I could boost top speed as well in a flank speed situation. My motor is 135 HP.
3) reasonable get-to-safety backup for me, which I currently lack.

If you price generated electricity at $0.50/kwh the economics start to look OK for my use case, which is 200+ days per year underway.

Comments?

ETA: quick calc says $4k per year in my pocket. Seems worth pursuing.

 

[mcarthur]

Jeff, rather than a sail drive you may be better off with either parallel hybrid off your existing diesel (is there one?) or if its mostly just a backup then even consider a 6kW or so outboard. Either one would mean no new holes in the hulls. If you go the parallel, then you can do the alternating diesel-electric: 1 hr diesel with alternator and electric motor in regen mode then 1hr electric only.
I have a spreadsheet which I'm playing with and I can get to 6 hrs electric, 2 hrs diesel in an 8hr day for 44nm total in good sun for solar.

For batteries, I'm going DIY EVE 280K or 304's along with one of the better BMS.

One other thing that start getting ouchy is the cabling - if you are going 10kW saildrive (assuming 10kW continuous) then at peak you are likely drawing 11kW from the battery (at a 90% transfer efficiency). That is 230amps. If your battery is, say, 2m from the motor which is a 4m round trip, then you are talking 3/0 or 4/0 wires. If you want a 48V alternator off the diesel helping recharge, and that's 2m away from the batteries then that would be 2AWG for a 6kW alternator putting out 5kW of power.

 

[Jeff F]

Jeff, rather than a sail drive you may be better off with either parallel hybrid off your existing diesel (is there one?) or if its mostly just a backup then even consider a 6kW or so outboard. Either one would mean no new holes in the hulls.

I have a single diesel ex work boat with nice flat sections aft. Not afraid of making holes, and some of the saildrives keep hull penetration to a minimum. Maybe 6 kw would be sufficient. I'm just exploring.

Not really interested in charging from my motor. Been down that path. See recent thread.

We all can customize individually to our needs on a DIY basis. That's the cool thing, as Weebles pointed out earlier.

 

[Jeff F]

Perhaps I should maximize solar and reduce battery and do 6 kw. Off to to some measurements

 

[mvweebles]

Perhaps I should maximize solar and reduce battery and do 6 kw. Off to to some measurements

I would think first step is an energy budget, then build to that with a margin for cloudy days and error; plus a factor for battery reserve-days. In this URL is a link to an Excel spreadsheet that is a good start. Looks like it's mostly DC loads, but expanding to AC would be easy.

Peter

 

[Jeff F]

I would think first step is an energy budget, then build to that with a margin for cloudy days and error; plus a factor for battery reserve-days.

I've got house needs pretty much covered now, although maybe a little thin with guests.

My 48v would be undertaken with two goals in mind:
1) providing reliable backup propulsion for my single screw boat, and
2) capture solar where feasible, and translate the energy into propulsion, reducing diesel consumption and GHG emissions.

Thanks for the comments. It helps me to more clearly refine my needs and hence a budget-oriented solution.

I should add that in general my approach is to fully refine a "what would I do now" solution, then revisit it at the next refit opportunity. These discussions help me, and others on the journey, I hope.

My solution is starting to look more like $5k batteries, $5k saildrive, and $10k solar. Saildrive is the only sunk cost, if set up properly.

I'm surprised nobody's challenged my $4k/yr number. Maybe I've put everyone to sleep...

 

[Jeff F]

On my last voyage I covered 10k miles and burned 2,200 gallons for propulsion.

If I implemented this system, maximizing solar, what would the next voyage look like?

Interesting question. Hope I'm not dragging the thread off.

 

[sunchaser]

On my last voyage I covered 10k miles and burned 2,200 gallons for propulsion.

No matter what you add in the way of solar, batteries or different drives, there is no denying you have a super efficient vessel. Given your vessel's current great nmpg might I suggest you focus on insuring the highest level of on board systems reliability and redundancy.

In other words, don't mess with a good thing.

 

[Jeff F]

Given your vessel's current great nmpg might I suggest you focus on insuring the highest level of on board systems reliability and redundancy.

I had some cases of sudden engine failure last season. Think I've finally fixed that, but it got me thinking of backup propulsion. 48v electric seems like a practical solution.

I've got room for more solar, and my existing array is a big hit.

I dunno. Maybe a big solar array will pay for itself in fuel savings?

I'm just spit balling here.

 

[Jeff F]

I was looking at this guy last night. A couple of holes through the bottom of my boat to install, and I'm sure 5 knots for me.

https://www.torqeedo.com/us/en-us/products/pod-drives/cruise-6.0-fp-torqlink/M-1269-00.html

 

[mcarthur]

The fine print there says input power: 6kW, propulsive power 2.7kW. I've never seen it quite said that way but I suspect there shouldn't be much loss in the straight through drivetrain. If so, then it's only a 45% efficient prop ... which doesn't equate to their "58% overall efficiency" statement either.

Also the prop speed of 1130rpm is pretty low for a 12" prop. May not be a problem running at 4kn, but probably is getting up to 6kn or more.

That efficiency question is odd, and the overall Torqueedo history in their smaller units in comments from people online hasn't been great. Hard to know how prevalent any issue is, and certainly not many pod's out there to compare with.

 

[Jeff F]

Appreciate comments.

There seem to be a wide variety of pods aimed at the new sailboat market, with a growing secondary market in repowers. Lots of action in that sphere.

I too am skeptical of power claims. Probably 10kw is where I'll fetch up. Or possibly a pair of 6kw. Agree that propping is a consideration. Torqueedo has several props available.

 

[Jeff F]

That efficiency question is odd, and the overall Torqueedo history in their smaller units in comments from people online hasn't been great.

I'm inclined to believe that expectations haven't been well managed in a lot of cases. We're in very early days, and I'm going off-label. Eyes wide open. But it's really an attractive system for me. And done right, I can rationalize the $$.

Edit to add: I've been using the crude metric of 10 kwh = 1 gallon diesel. I think we've established that for diesel -> DC. I think that could be used to approximate DC power to prop. Haven't really dug into it.

 

[Jeff F]

One more thought. It appears that my stern thruster is pretty much shot. I've been planning to repair it to the tune of $3k.

Maybe I should pop in a couple of 6kw pods, widely spaced, and abandon the stern thruster.

 

[rslifkin]

The fine print there says input power: 6kW, propulsive power 2.7kW. I've never seen it quite said that way but I suspect there shouldn't be much loss in the straight through drivetrain. If so, then it's only a 45% efficient prop ... which doesn't equate to their "58% overall efficiency" statement either.

Also the prop speed of 1130rpm is pretty low for a 12" prop. May not be a problem running at 4kn, but probably is getting up to 6kn or more.

That efficiency question is odd, and the overall Torqueedo history in their smaller units in comments from people online hasn't been great. Hard to know how prevalent any issue is, and certainly not many pod's out there to compare with.

The low prop RPM makes me think that like a lot of the other electric drive stuff currently available, they're optimizing for low speed thrust, not ability to go fast.

 

[mcarthur]

The low prop RPM makes me think that like a lot of the other electric drive stuff currently available, they're optimizing for low speed thrust, not ability to go fast.

Yes, my thought too. Works decently, perhaps really well, for heavier vessels at low speeds, say around 3-5knots. Could even deal with the silly wind against tide/lee shore/9,000mph super hurricane argument decently for as long as your battery lasts.

 

[Jeff F]

The Torqueedo thrust prop is optimized for 6-7 knots IIRC. Seems about right for me. Since I have to go with an offset mount I think twins make sense.

 

[Jeff F]

Edit to add: I've been using the crude metric of 10 kwh = 1 gallon diesel. I think we've established that for diesel -> DC. I think that could be used to approximate DC power to prop. Haven't really dug into it.

Coming back to this, I know
a) how fast/far I can go right now on a gallon of diesel.
b) that I could generate 10 kw from that same gallon of fuel

So I *think* my 10kw boat speed should be very close to my 1 gph boat speed. Pod prop is more highly optimized and in clean flow.

That's kind of where they're going to get their diesel equivalent numbers I think. They're suggesting 12 kw = 20 HP. I'm getting pretty close to that too.

 

[rslifkin]

Giving some thought to your situation Jeff, would it make sense to use outboards instead of pods on your boat? That way you could get the props out of the water when running on diesel and avoid the extra drag. By the same logic, if it weren't for the cost issue, it would be nice to have a feathering or controllable pitch prop on the main shaft to reduce drag when running in electric mode.

 

[Jeff F]

I'm kind of thinking I'd often run with both diesel and electric. So at my usual 7.5 knots instead of burning the usual 1.5 gph I'd throttle back to 1 gph and blend in 5 kw solar and maintain the same speed. Or 0.5 gph and 10 kw if I've got excess power.

Maybe this is off base, but it sounds feasible. I hang my dinghy on the transom, and don't want outboards back there as well, plus propping etc is a concern. I have a yanmar SD on my sailboat and like it.

I was looking at this guy more recently. Two 6.0 kw units. https://www.epropulsion.com/pod-drive/

 

[rslifkin]

I'm kind of thinking I'd often run with both diesel and electric. So at my usual 7.5 knots instead of burning the usual 1.5 gph I'd throttle back to 1 gph and blend in 5 kw solar and maintain the same speed. Or 0.5 gph and 10 kw if I've got excess power.

Maybe this is off base, but it sounds feasible. I hang my dinghy on the transom, and don't want outboards back there as well, plus propping etc is a concern. I have a yanmar SD on my sailboat and like it.

I was looking at this guy more recently. Two 6.0 kw units. https://www.epropulsion.com/pod-drive/

On that thought, other than not gaining anything in the maneuverability department, what about attaching one of the inboard electric motors (ELCO and Epropulsion both make them) to the shaft so the electric and diesel drive go through one prop? That gives no extra underwater drag from the setup and you'd still have prop wash over the rudder for better steering if running electric only. Only thing I'm not sure of is whether the control systems for those motors would work well with another power source on the same shaft.