Xpm-78 -All the amenities/No generator

Wayne's latest post is on the DC Battery-Based electrical system for our new custom 78-foot aluminum extreme expedition passage maker (XPM-78) under build in Turkey.

All electric galley, washer/dryer, and two techie nerds with lots of tools and toys.

Lots of solar and big alternators, but we will have NO generator.

Everything is theoretical since we've never done this before, so we're very interested to learn from your comments.

Check out the electrical diagram here:

https://mobius.world/tech-talk-xpm78-mbius-electrical-system-overview/

Wow, 14x360W solar panels is a lot of surface area!

From a guy with a boat that got caught in Dorian and had his two big solar panels blown off the mounts, how will you be sure the solar will withstand possible very high wind loads?

Granted, mine were probably not mounted as securely as they should have been, and if I was close to the boat I would probably have removed them and stored them inside the boat, but just wondering how y’all plan to mount your solar.

Great stuff, as always. And what would a reply be without a few questions? ......

I’m curious how you envision operating on 60hz shore power with a 50hz boat? Assuming your inverters are programmed to 50hz, they will only
Lock on to 50hz shore power. Alternately you can open up the acceptable input frequency really wide to accept both 50 and 60hz. But if you do that then the 60hz shore power will pass through yielding 60hz on board rather than your native 50hz. This implies that all the onboard loads are 50/60hz agnostic.

Oops, that was only one question.

Personally I wouldn’t be comfortable without a generator, if go no other reason than to provide a backup power source.

And I’m really envious of your 5kw of solar.

I’m also interested that you have separate inverter systems for 120 and 240v. The alternative is to use an auto transformer or just a reduction transformer off a 240v inverter system. Curious what your thinking is on this. I have personally become very sensitive to the standby power draw of the Victron’s, all of which run all the time. Others like outback idle parallel inverters and bring them online progressively as loads demand.

I have 6 x 345W solar, 2 x 200A engine alternators and a house bank of 1284Ah @ 12v. And no generator. So, a scaled down version of what is planned for the xpm78. I have a propane galley, but refers are 12V. They are the biggest draws.

After a six years of use, a few observations are:
1. weaker winter irradiance and/or angle means noticeably less solar Ah replacement. In higher latitudes this would be accentuated unless the panels can be tilted.
2. If I get panel shading, and that occurs with SE winds at anchor for me, then solar will not match daily use in winter. Down here in Oz the SE trades blow all winter, so it is an issue!
3. Moving after a few nights at anchor allows the house bank to be boosted enough for the solar to cope. But if you want to spend a week somewhere, other than in low latitudes in warmer months, then you need to do serious power management (saving) on board.
4. I have the ubiquitous Honda 2000 for backup, and on average over a year I use it 5-10% of time anchored. All things considered I would install a 5kW genny if doing it again.

For the schematic on the blog, there is a typo. Alternators are "250V @24V" should obviously be "250A @24V".

Using inverter/chargers would not be my choice next time. I would seperate the functions. So, both 230V and 120V inverters (at 50Hz and 60Hz respectively) and Victron's universal input chargers (90-265V, 50/60Hz). Wiring & switching is more simple.

As TT notes, parasitic loads add up and its not just the Victron's. eg Sat dish always on in case I've set the PVR to record something, TV on standby, laptop plugged in, USB chargers plugged in for phone/ipad charging, router and switches running. It ends up being a surprising amount, and too much of a PITA to be running round turning off/on etc. Easier to have a larger house bank and more charging options. Hence the genny.

" I have a propane galley, but refers are 12V. They are the biggest draws."

A switch to propane reefers would cancel the biggest electrical load on most boats.

Second choice would be custom built super insulated (4-6 inches) and eutetic plates.

These could be engine charged or solar tho the engine driven seem to do better with freezer temps 0-F plates with -10F needed to charge . The downside is the plates and thick insulation take up a lot of room.


Air cond only under way?

For comparison my 1,500 SF Florida condo uses 12 kWhr per day on average during the winter months. No air conditioning or room heat and all other loads are comparable to your boat: electric stove, washer dryer and water heater for two, TV, router all on 24/7, etc.

A 5 kW solar panel should put out 20 kW on an average sunny day so you should be in balance with your solar capability in most latitudes even with cloudy days and even if you don't move and supply power with the engine alternators.

Since your hot water is electric (except presumably when you have run the propulsion engine recently), consider installing a heat pump hot water heater. Should cut your hot water energy usage in half, although these don't typically have a coil for engine heat. Depends on your ratio of hanging out on the hook vs underway whether it helps or not.

David

As echoed by others, a genset install may prove helpful more often than not. My 12.5 kW unit in its sound shield measures 23"x40"x26" with a 5kw unit for sure smaller. A lot more money can be spent trying to avoid a genset than installing one.

I think their plan is to use the main as the genset, when required. That’s a pretty common sail boat approach, and is perfectly viable with an accompanying set of trade offs. But as a infrequently used power source, I don’t think it’s a bad approach. My biggest concern would be having a backup if there is some issue with the main engine charging system. Then you only have solar, and there WILL be times when it’s not enough. But a little portable screamer may be all that’s needed as a backup. Hopefully Wayne will be able to share his thinking soon. He’s probably typing away.

If the boat is set up to live off the batteries the shore power is simple, you just need it to run a battery charger.
Hz problem solved.
We had no generator on the sail cat, just big alternators and solar. I didn't want air conditioning and three small diesel engines seemed one too many. However running a 38hp diesel to charge the batteries is easier to justify than 120hp or 300hp on a trawler.
We also had a propane fridge but having a pilot light going the whole time plays on your mind. When it failed in Thailand we replaced it with another 12v

"We also had a propane fridge but having a pilot light going the whole time plays on your mind."

A proper installation is safe ,a poor one is never safe.

The pilot light is doing refrigeration 24/7 the energy is not lost .

Thats how a 20lb bottle can last a month (with cooking too) with a home sized reefer on board..

The number one safety label you see on boats in New Zealand is "turn the gas off at the bottle"
It is really good advice and saves lives.
With a propane fridge you can't do that, plus you have a pilot light going.
Even though we had one for two years of continuous use I didn't like it.
To me it is RV technology where, when you have a leak, the gas eventually drains outside, not into the bilges.

I like it.

I like the redundancy of the separate 120v and 220v inverter banks, although being from Australia where the standard supply is single-phase 240v/50Hz, I would delete the 120v system completely and just use 240v appliances. Nearly all guest 'plug in' chargers etc. are voltage/frequency intolerant these days.

At this point in the design phase, I would definitely explore running the house DC system at 48v rather than 24v. The current draw on the DC bus in a "everything off the inverters all the time" system is massive, and I like the reduction in current at 48v. It also seems to make for an easier transition to lithium-based battery banks later if the system is already 48v nominal.
Another DC-DC converter for the 24v bus is easy.

Awesome looking boat!

cardude01 said:

Wow, 14x360W solar panels is a lot of surface area!

From a guy with a boat that got caught in Dorian and had his two big solar panels blown off the mounts, how will you be sure the solar will withstand possible very high wind loads?

Granted, mine were probably not mounted as securely as they should have been, and if I was close to the boat I would probably have removed them and stored them inside the boat, but just wondering how y’all plan to mount your solar.

Click to expand...

Sorry for taking so long to responds here "Cardude". We can relate all too well to your concern about solar panels and other equipment when your boat is caught in severe weather. When I was singlehanding my steel sailboat around the world I had quite the experience when the tsunami hit Pango Pango in American Samoa almost 10 years ago to this day. (Sept. 29, 2009) and then when Christine and I happened to be hauled out in Fiji, doing a huge refit to that same 52' steel Bruce Roberts cutter, when Winton hit and we experienced winds reportedly over 220kmh and were actually "knocked down" when the big steel support stands underneath gave way.

Those experiences taught us well to take such situations into account as we designed the new boat and we have several ways of protecting the solar panels in a cascading degree of severity of conditions. The first stage is "just" eXtremely strong mounting of the panels to the boat. We have three "banks" of solar cells, one bank of 3 up front on top of the PH roof that are mounted on a dedicated single frame which in turn is mounted very solidly to the aluminium superstructure of the PH. Then there is a bank of 8 solar panels which also act as the roof panels on the roof over the SkyBridge which is a single welded structure of rectangular aluminium extrusions. These 8 panels are held in place with a combination of bolts through the AL extrusions and industrial adhesive. Then the aft 3 panels are mounted to the aluminium roof which is pat of the PH superstructure itself which forms a overhanging roof above the deck to the rear of the PH. All these panels should be able to withstand weather and sea conditions we experience 90+% of the time.

For the exceptional scenarios, our practice is go into what we call "hunkered down" mode where we remove any and all gear that can be removed and additionally secure that which cannot. For example, we have gone to great lengths to design and now build the roof overtop the SkyBridge to be able to fold down such that its whole perimeter is down resting atop the coaming and can be secured there. We designed in this feature as part of a larger system where the whole arch assembly is hinged and we can lower our air draft dramatically to enable us to go cruise canals or other situations where there are low height restrictions. This same capability also serves us well when we want to go into this "hunkered down" mode such as we would do if we were to leave the boat for an extended time in a location within hurricane/cyclone zones.

You will be seeing more of this articulated fold down roof/arch system in the coming weeks here as we start mounting the roof.

-Wayne

twistedtree said:

Great stuff, as always. And what would a reply be without a few questions? ......

I’m curious how you envision operating on 60hz shore power with a 50hz boat? Assuming your inverters are programmed to 50hz, they will only
Lock on to 50hz shore power. Alternately you can open up the acceptable input frequency really wide to accept both 50 and 60hz. But if you do that then the 60hz shore power will pass through yielding 60hz on board rather than your native 50hz. This implies that all the onboard loads are 50/60hz agnostic.

Click to expand...

Hi Peter, thanks for stopping by as I'm sure things are very busy for you as well as your new build progresses.

Great question and I will cover this in more depth in coming Tech Talk posts on the blog but short answer (for me) is as follows. Given that we very rarely ever have shore power and when we do it is usually when we are leaving the boat for some time, the first way we deal with 50/60Hz supply is via the different inverters. The three 220 inverters will be 50Hz and the two 120V will be 60Hz, so this will cover us in probably more than 95% of the time.

On those occasions when we do plug into shore power, all of it comes aboard through the Isolation Transformer which gives us the ability to chose and match any voltage we want for input/output from 120-240V, but of course does not directly address your question about Hz. What we are doing to have both Hz onboard when on shore power is to have the shore power supply ONLY the charge side of the inverters and have ALL AC output coming from the inverters only. This is why in the Electrical Summary article on the blog, I've characterised our electrical system and our boat as being "Battery Based". With no generator and no shore power supplied AC onboard, we have no "inverter only" load switch as everything is "inverter only". In this setup, shore power is only used to run the battery chargers, which can accept 50 and 60Hz and then all the AC (and DC) comes from the batteries.

In the little diagram I made for the Electrical System Overview article, you can see that coming out of the Isolation Transformer, the AC power goes directly to the AC input of the inverter/chargers and is only used for the charger side of the MultiPlus units, not passed directly through.

Your question has pointed out to me that I forgot to label the diagram in the TT post to have the Hz for the AC outputs so I will go and update that. Thanks.

I fully understand that this type of setup would not make sense for many/most boats as they are much more often plugged into shore power or running a genset, but for our use case this is what we think will work best.

Make sense to you? Raise any concerns? I would certainly welcome and appreciate any and all questions and suggestions you would have as you are certainly for more experienced and expert in such matters.

Thanks!
Wayne

"To me it is RV technology where, when you have a leak, the gas eventually drains outside, not into the bilges."

When installed in a vessel the fridge is secured above the water line and in a deep lipped pan , with an overboard drain.
We placed ours in the cockpit that is self draining .
PIA in the AM getting breakfast goodies , but great in the PM for a cold beverage.


Never a dead battery .

Whodgins said:

In the little diagram I made for the Electrical System Overview article, you can see that coming out of the Isolation Transformer, the AC power goes directly to the AC input of the inverter/chargers and is only used for the charger side of the MultiPlus units, not passed directly through.

Click to expand...

Hi Wayne,


If I'm following you correctly, I don't think the Multiplus devices operate the way you want them to. Or maybe I don't understand them either...


But my understanding is that they are always either inverting OR charging, but never both. They can be set up to only charge, but in that case they will not invert.


I think you want them to invert at 60hz on the output side, while simultaneously accepting 50hz on the input side and using that to charge. But I believe they can only do one of those things at a time.

Wayne
When contemplating a new build FPB the discussions around inverters, gensets and get home engines were interesting. When in NZ we talked with the folks in Whangerei about various subtleties of these combinations. Each prospective owner had a slightly different take on the various combinations.

Given Steve's decade plus of many FPBs I'd guess you've got his current thinking based upon field experience? As I recall he removed his genset from his big sailboat. But, his first FPB Windhorse came with a genset I believe.

Your clean sheet build is to be applauded and presents great reading on boat building 101. Along with Peter's posts over the years lots to learn on TF for the inquisitive.

Whodgins said:

In the little diagram I made for the Electrical System Overview article, you can see that coming out of the Isolation Transformer, the AC power goes directly to the AC input of the inverter/chargers and is only used for the charger side of the MultiPlus units, not passed directly through.

Click to expand...

That's not how they work.

A Multiplus will actually pass directly through the AC source when connected.
It can boost this using the inverter as well, but in general operation, when AC is present at the input, that AC is switched through to the output.
The charger will also operate and charge the batteries when AC is present.

The better way to become shore-power intolerant as far as frequency and voltage, is to replace the Multiplus units with straight inverters, and add a bank of multi-voltage/multi-frequency chargers. This way it will work as you have stated; shore power will only charge the batteries, and your ship loads will only ever see inverter output AC.

twistedtree said:

Oops, that was only one question.

Personally I wouldn’t be comfortable without a generator, if go no other reason than to provide a backup power source.

And I’m really envious of your 5kw of solar.

I’m also interested that you have separate inverter systems for 120 and 240v. The alternative is to use an auto transformer or just a reduction transformer off a 240v inverter system. Curious what your thinking is on this. I have personally become very sensitive to the standby power draw of the Victron’s, all of which run all the time. Others like outback idle parallel inverters and bring them online progressively as loads demand.

Click to expand...

Quite right Peter that having a generator adds another layer of redundancy or backup for onboard AC power and we thought long and hard about it as we designed Möbius. Our thinking is that we have two independent "generators" onboard in the form of our two ~6kW alternators on the Gardner. Granted, this makes Mr. Gee our Gardner, a single point of failure, but we think the probability of loosing the engine or both alternators is acceptably low.

I'm glad you brought up the question about inverters vs autotransformers and I would REALLY appreciate knowing your thoughts on the pros/cons of each and which way you are going on your new build? I'm a bit undecided as to the best route to go for the 120V via inverter vs Autotransformer and we have not placed the Victron order quite yet but need to soon.

I've worked through the parasitic “No loads” which the Victron inverters have and have convinced myself at least that these are manageable with a combination of running only as many inverters as needed for a given situation, just one at night on anchor for example, and then using some of Victron’s “Search Mode” to reduce the “no load” drains. I don’t have any personal experience with these settings yet so if you or others have direct experience with these MultiPlus inverter/chargers I would sure appreciate you sharing it On our previous boat I just ran our MultiPlus units with AES (Automatic Economy Switch) turned on which as per Victron: “If this setting is turned ‘on’, the power consumption in no-load operation and with low loads is decreased by approx. 20%, by slightly
'narrowing' the sinusoidal voltage. Applicable in stand-alone configuration only.”. However on the new boat I will experiment with the additional “Search Mode” option which again as per Victron manuals is “If search mode is ‘on’, the power consumption in no-load operation is decreased by approx. 70%. In this mode the MultiPlus, when
operating in inverter mode, is switched off in case of no load or very low load, and switches on every two seconds for a short period. If
the output current exceeds a set level, the inverter will continue to operate. If not, the inverter will shut down again.
The Search Mode “shut down” and “remain on” load levels can be set with VEConfigure.
The standard settings are:
Shut down: 40 Watt (linear load)
Turn on: 100 Watt (linear load)”

Again, I look forward to your much more informed opinion and what you are doing regarding things like these parasitic loads. You mentioned that “Others like outback idle parallel inverters and bring them online progressively as loads demand.” And I’m not sure how this is different than the MultiPlus “Search Mode” and would appreciate any help with understanding the differences.

I should also mention that being a “Battery Based” boat, DC is our primary voltage, both 24 and 12 and so where given the choice we have 24V DC equipment rather than 220v AC so in many situations we can simply turn the inverters off. For example all our navigation equipment is running off 24DC, we are all PC based with Furuno and TimeZero so no MFD. All our many monitors are all 24V DC as are all our personal techie devices running on 24V DC. Hot water primarily comes from our Kabola diesel boiler and/or the heat exchanger from the Gardner when he is running so no AC needs there for domestic hot water or our in floor heating. We do have a 240V heating coil in our calorifier so that’s always an option if we are on shore power or need such a load. However we definitely have our share of equipment that requires AC such as all electric cooking (induction hob, smart oven and BBQ) and washing machine. We do have the cabinets and infrastructure for a dishwasher and dryer but we prefer to not have these onboard, a very personal decision I appreciate, but then what decision in building a boat isn’t?

Thank for the great questions Peter, that’s one of the biggest values and reasons for blogging and posting right?

- Wayne

twistedtree said:

Hi Wayne,


If I'm following you correctly, I don't think the Multiplus devices operate the way you want them to. Or maybe I don't understand them either...


But my understanding is that they are always either inverting OR charging, but never both. They can be set up to only charge, but in that case they will not invert.


I think you want them to invert at 60hz on the output side, while simultaneously accepting 50hz on the input side and using that to charge. But I believe they can only do one of those things at a time.

Click to expand...

Pretty much correct.
When supplied with AC; the Multiplus will switch through the supply AC to the output side, and also use the AC to run the charger; charging the batteries.
The Multiplus can also 'boost' the output by using the inverter to assist, giving higher peak-load handling when on limited-current shore power, but generally, on a Multiplus, if there's AC present at the input, that AC is passed through to the output.
The neutral-earth bond is also opened at the Multiplus; relying on the supply source's neutral-earth bond.
When operating purely as an inverter (no AC input present); the neutral-earth is bonded at the Multiplus output.

FF said:

"To me it is RV technology where, when you have a leak, the gas eventually drains outside, not into the bilges."

When installed in a vessel the fridge is secured above the water line and in a deep lipped pan , with an overboard drain.
We placed ours in the cockpit that is self draining .
PIA in the AM getting breakfast goodies , but great in the PM for a cold beverage.


Never a dead battery .

Click to expand...

That's probably about as good as can practically be done. But anyone considering this should know that it doesn't meet any of the safety standards for propane on a boat. Something like a fridge or a space heater that operates and cycles on it's own needs to have the combustion chamber and intake and exhaust totally sealed off from the vessel interior, and only drawing/exhausting to the exterior. And there are requirements on the intake and exhaust to ensure gas doesn't find it's way into the boat through other means.

Insequent said:

I have 6 x 345W solar, 2 x 200A engine alternators and a house bank of 1284Ah @ 12v. And no generator. So, a scaled down version of what is planned for the xpm78. I have a propane galley, but refers are 12V. They are the biggest draws.

After a six years of use, a few observations are:
1. weaker winter irradiance and/or angle means noticeably less solar Ah replacement. In higher latitudes this would be accentuated unless the panels can be tilted.
2. If I get panel shading, and that occurs with SE winds at anchor for me, then solar will not match daily use in winter. Down here in Oz the SE trades blow all winter, so it is an issue!
3. Moving after a few nights at anchor allows the house bank to be boosted enough for the solar to cope. But if you want to spend a week somewhere, other than in low latitudes in warmer months, then you need to do serious power management (saving) on board.
4. I have the ubiquitous Honda 2000 for backup, and on average over a year I use it 5-10% of time anchored. All things considered I would install a 5kW genny if doing it again.

For the schematic on the blog, there is a typo. Alternators are "250V @24V" should obviously be "250A @24V".

Using inverter/chargers would not be my choice next time. I would seperate the functions. So, both 230V and 120V inverters (at 50Hz and 60Hz respectively) and Victron's universal input chargers (90-265V, 50/60Hz). Wiring & switching is more simple.

As TT notes, parasitic loads add up and its not just the Victron's. eg Sat dish always on in case I've set the PVR to record something, TV on standby, laptop plugged in, USB chargers plugged in for phone/ipad charging, router and switches running. It ends up being a surprising amount, and too much of a PITA to be running round turning off/on etc. Easier to have a larger house bank and more charging options. Hence the genny.

Click to expand...

Thanks for the thoughtful response and sharing your setup Brian and sorry to take so long to respond. Time is at a premium as the build progresses and launch date approaches. Hopefully!

I value such first hand knowledge and experiential learning about the highest of any and it is in rare supply so much appreciated. Re your points:
1. Yes, there is quite a range of solar output in different seasons, locations and weather though the newer panels and MPPT controllers are improving this more and more. I did a bit of computer modeling of our panels in different locations and dates but more so gathered as much real world data as I could find over the past many years from others who have solar on their boats to get as realistic a guesstimate as possible for the output we an expect. I will cover this in more detail when I write the Tech Talk article on our solar setup but the result of my analysis is that we should be able to expect a low of 15kW and a high of 21kW per solar day. I've then factored this expected solar output as well as our estimated "worst case" maximum 24hr consumption rates, both at anchor and on passages of 9-12kWh and used these to of into the sizing of the battery bank. Time will tell how well these theoretical calculations measure up against the real world when we get out there.
2. Being a very “global” boat with no location for any extended periods of time, I have tried to size everything to work in pretty much any location and season. I’m not going to say that there are no situations where we might wish for more but I think they will be relatively few and far between.
3. Yes, our years of living full time onboard our previous boats has taught us to be very good power mizers and energy frugal in all regards. We do have the significant benefit of those two 6kW alternators on our main engine so they will add a lot of charge quite quickly whenever we are on the move and of course we can fire up the Gardner at any time at anchor as well, though I have tried to build the system to not require this much at all.
4. We had a 6kW Northern Lights generator on our previous boat and used it extensively though less and less as we added more and more solar and other improvements and in the end we went without it for the last year we lived aboard. As I noted above and to Peter earlier, we think that our 12kW alternator output will give us a good backup “genset” if needed and more than enough charging capacity when underway and we think we have enough solar output to keep our batteries topped up almost every day on anchor.

Thanks for catching that typo on the alternators and I will update that illustration as soon as I can.

I had very similar thoughts about separating the charging and inverting to dedicated units but in the end there were so many shared components that I think it best for us to go with the combined MutiPlus. I’ve had them before and I think the wiring and switching is actually easier with the combined units vs separate.

We have built the overall electrical system with much of the scenarios you outlined and have made it as easy as possible to reduce the PITA of running around as you captured it well. And we’ve done as you noted by sizing the overall electrical system with a larger house bank and more charging options, though just the 2 in our case; solar and alternators.

Thanks Brian,
- Wayne

FF said:

" I have a propane galley, but refers are 12V. They are the biggest draws."

A switch to propane reefers would cancel the biggest electrical load on most boats.

Second choice would be custom built super insulated (4-6 inches) and eutetic plates.

These could be engine charged or solar tho the engine driven seem to do better with freezer temps 0-F plates with -10F needed to charge . The downside is the plates and thick insulation take up a lot of room.


Air cond only under way?

Click to expand...

Hi FF, pretty much match your experience and suggestions I think. We have designed Möbius to be a "single fuel" boat, so no propane or gasoline and we have always had good success with DC reefers and are going that way again with the new build. We went mostly with your "second choice" and have built super insulated cabinets for our 2 fridges and 2 freezers which themselves are already quite well insulated. All 4 units are running on remote compressors below the floor in the basement which enables us to build the cabinets in this way with no air circulation required around the reefer units themselves.

I considered eutectic plates but decided that individual DC Danfoss compressors and super well insulated fridge/freezer compartments would work best for us. Part of my thinking was what you mention of plates taking up a lot of your reefer volume and more so it was not wanting to have to run the engine to run the compressor when at anchor.

We expect to be able to run our AirCon at anchor or underway and have sized our battery and charging systems accordingly. The biggest factor in making this possible is that we have insulated the boat to mimic a Thermos bottle and so our AC loads are very minimal when we do chose to use them, which doesn't tend to be too often for us. We rely more on very good and both passive and active ventilation to give us great air movement at all time so it makes living aboard very comfy almost all the time we are at anchor in tropical climates, where we have easily spent the most of our years sailing.

- Wayne

djmarchand said:

For comparison my 1,500 SF Florida condo uses 12 kWhr per day on average during the winter months. No air conditioning or room heat and all other loads are comparable to your boat: electric stove, washer dryer and water heater for two, TV, router all on 24/7, etc.

A 5 kW solar panel should put out 20 kW on an average sunny day so you should be in balance with your solar capability in most latitudes even with cloudy days and even if you don't move and supply power with the engine alternators.

Since your hot water is electric (except presumably when you have run the propulsion engine recently), consider installing a heat pump hot water heater. Should cut your hot water energy usage in half, although these don't typically have a coil for engine heat. Depends on your ratio of hanging out on the hook vs underway whether it helps or not.

David

Click to expand...

Appreciate the real world data and your experiences David, thanks.

Our estimated max daily energy consumption ranges from 9-12kWh so not too far off your estimates. We have gone to great lengths to over insulate all the living spaces and so that should increase our efficiency dramatically when it comes to AirCon and heat requirements so we think we are sized to be able to have AirCon/Heat within our daily estimates and be able to supply all that via our solar and alternators.

Our primary energy source for hot water is actually diesel, via our Kabola diesel boiler which is extremely efficient and gives us almost no electrical demand for hot water production. We do make lots of long passages but in the overall time in a year we are easily at anchor the vast majority of the time so we have designed and sized all the systems primarily for at anchor scenarios.

- Wayne

sunchaser said:

As echoed by others, a genset install may prove helpful more often than not. My 12.5 kW unit in its sound shield measures 23"x40"x26" with a 5kw unit for sure smaller. A lot more money can be spent trying to avoid a genset than installing one.

Click to expand...

I think that for most boats and people a genset makes lots of sense and we had a 6kW Northern Lights on our previous boat.

However for our new boat we don't think a genset is needed and the reduced maintenance of one less system is a big plus. No doubt we have invested a bunch of the budget on all that EPDM insulation and other ways of making this boat super efficient but we see this as just that, an investment in the boat overall and one that will continue to pay us very nice dividends every day we are aboard.

I'm not "anti-generator" or any other setup, just doing my best to design systems and an overall boat that is the best Goldilocks just right, just for us, fit and so for us a genset isn't needed.

twistedtree said:

I think their plan is to use the main as the genset, when required. That’s a pretty common sail boat approach, and is perfectly viable with an accompanying set of trade offs. But as a infrequently used power source, I don’t think it’s a bad approach. My biggest concern would be having a backup if there is some issue with the main engine charging system. Then you only have solar, and there WILL be times when it’s not enough. But a little portable screamer may be all that’s needed as a backup. Hopefully Wayne will be able to share his thinking soon. He’s probably typing away.

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Guilty as charged TT, both Christine and I are former sailors so no surprise this is very much a "motorboat designed by and for sailors" in many regards and our overall electrical system design certainly reflects this.

Also quite right that we see the 12kW total output from our dual 240A @ 24V alternators on the main engine to be our "genset" when needed and when underway and that our 14 solar panels are our primary source of charging the batteries. As per the diagram of the Electrical System in the blog post my current design is to have an MPPT controller for each solar panel so this will increase the overall solar efficiency and reduce the effects of shading of any of the panels.

I'm sure that there will be times as you noted when solar output on a given day isn't enough but with the Carbon Foam batteries able to go down to such a low SoC (20% or less) and that they can be at any PSoC for prolonged periods with no impact to their SoH (State of Health), I think we have a system that will deal well with times when solar output isn't enough.

Our "backup" or "genset" is our two alternators and with just a single engine that does create a dependency on the engine and a potential single point of failure. But we think that Mr. Gee, our Gardner 6LXB is about as reliable an engine as exists so we've reduced the probability of such a failure to a point that is acceptable to us.

And as you guessed, though I'm late getting to it, I am typing away here trying to catch up with these responses and ones over on the blog. The build consumes almost all of my time and attention and more so than ever of late so I quite enjoy this "distraction" and just needed to carve out some time to respond here. Thanks for your patience!

-Wayne

darkside said:

If the boat is set up to live off the batteries the shore power is simple, you just need it to run a battery charger.
Hz problem solved.
We had no generator on the sail cat, just big alternators and solar. I didn't want air conditioning and three small diesel engines seemed one too many. However running a 38hp diesel to charge the batteries is easier to justify than 120hp or 300hp on a trawler.
We also had a propane fridge but having a pilot light going the whole time plays on your mind. When it failed in Thailand we replaced it with another 12v

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We seem to be very like minded in our thinking. Had propane fridges in past RV's and campers but don't think they make sense on a boat and we also wanted to go "single fuel" with this boat so no gas or propane aboard the new boat. Reefers are all 24V DC.

Been following that amazing build...

nitrolx said:

I like it.

I like the redundancy of the separate 120v and 220v inverter banks, although being from Australia where the standard supply is single-phase 240v/50Hz, I would delete the 120v system completely and just use 240v appliances. Nearly all guest 'plug in' chargers etc. are voltage/frequency intolerant these days.

At this point in the design phase, I would definitely explore running the house DC system at 48v rather than 24v. The current draw on the DC bus in a "everything off the inverters all the time" system is massive, and I like the reduction in current at 48v. It also seems to make for an easier transition to lithium-based battery banks later if the system is already 48v nominal.
Another DC-DC converter for the 24v bus is easy.

Awesome looking boat!

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We thought about going 220V only for many of the reasons you noted but we think that the added flexibility of being able to have some 120V appliances and equipment onboard as well as able to accommodate guest items which may need such, was worth the relatively small cost and complexity of having the 120V inverters. I'm seeing the same thing as you with more and more devices being able to accept any voltage range and we are also seeing more and more of the larger AC based appliances being 50/60Hz agnostic. So I think these concerns will continue to decline more and more over the next 10 years.

I thought long and hard about going 48V but don't think it makes sense for us at least, even with a new build. No question that the reduced current on a 48 vs 24 volt system would be a big plus and reduce cable sizes but we've been able to create an overall wiring setup with no more than 3% voltage drop anywhere using an all 24V system. When considering a 48V system there seemed to me to be just too many instances where we would need to convert down to 24V and some 12 in places, all with their inherent losses and costs and maintenance, so I've elected to stay with 24.

The benefits of Lithium, while many and significant, don't match up well with our use case and I don't see this changing in the future. I made the call to go with Carbon Foam as I believe these give us all the advantages of both Lithium and traditional FLA/AGM/Gel batteries with almost none of their respective limitations. Weight for example, which Lithium has a major difference, is not only not a factor for us, we actually wanted and benefited by the weight of the Carbon Foam batteries by containing them in dedicated battery compartments which are integral with the hull and on either side of the massive Keel Bar running the length of the boat, so the 835kg of our batteries acts as ballast and improves our ride and stability.

The use case and construction of these XPM boats are definately different that most others where things such as Lithium would be a better choice, but in our case the 24V Carbon Foam based system seems to be the best match.

- Wayne