Choosing the right performance cruising cat for Uhuru.

[CapDave]

I know this is a tough question because everyone's power consumption is unique, but we have our boat spec'd with 3.2 kW of fixed glass panel solar in elevated composite frames with individual controllers for shading, and a battery bank of 600 Ah at 48V (28.8 kWh), so with that hardware how close to running fully off of solar do you feel we could achieve (on a scale from 1-10 with 10 being completely autonomous)

We rarely use A/C unless in a marina hooked to shore power, maybe to cool the master hull off on the occasional night when it's unbearable...or the nights my wife tells me to turn it on. The boat will not have a generator but will be equipped with dual Integrel chargers to further mitigate the use of diesel and help with autonomy.

Thanks for you input!

I can't answer your question because it takes a lot of data to answer it, which you likely have or can get, but isn't in your post.

The best way to answer this question is very labor intensive. Using a spreadsheet app, make a list of every electricity consumer on your boat in one column, and it's demand in Watts in the next column. Then estimate how many hours/24 hour day you use each consumer in the next column. Write a formula in the next column that multiplies those last two columns and you get Watt Hours for each consumer for 24 hours. Then add that last column vertically, and that's your whole boat Wh consumption for 24 hours. Then apply a Capacity Factor to the Wh rating of your panels - based on your latitude and weather regime - to approximate their 24-hour output. In the tropics, the capacity factor might be 20% - lots of sun, short days, high temps....And of course shading counts.

So with your 3.2Kw of panels maybe you're generating something like 15KWh/24 hours....Compare that with your consumption spreadsheet, and you have the answer....

Sorry if I'm telling you stuff you know....

On our boat we have 840W of panels, and in the tropics that will run everything on the boat except the watermaker. We run engine/alternator/inverter to make water. We have a small token AirCon that only runs at the dock, it's pretty useless anyway.

 

[Zonker]

What is your CONSUMPTION like??

Our 40' boat had 0.5 kW of rigid panels / 450 A.hr battery @ 12V.

We didn't have a chart plotter so didn't run that 24/7 at anchor or on passages. We had a 12V Spectra watermaker and a small, very well insulated fridge. Wife was sometimes on the computer (12V Intel NUC/19" monitor) for 8 hrs a day. SSB/Pactor modem. Relatively low powered autopilot. Those were the big power consumers.

We did fine. On rainy days we had enough for a few days without any solar coming in. Running the engine to make power was reserved for places where it rained every day for a week and eventually we'd get behind. Probably put on 40 hours engine run time over 8 years of owning the boat because not enough solar. i.e. so minimal we didn't think about it.

 

[ol70]

I can't answer your question because it takes a lot of data to answer it, which you likely have or can get, but isn't in your post.

The best way to answer this question is very labor intensive. Using a spreadsheet app, make a list of every electricity consumer on your boat in one column, and it's demand in Watts in the next column. Then estimate how many hours/24 hour day you use each consumer in the next column. Write a formula in the next column that multiplies those last two columns and you get Watt Hours for each consumer for 24 hours. Then add that last column vertically, and that's your whole boat Wh consumption for 24 hours. Then apply a Capacity Factor to the Wh rating of your panels - based on your latitude and weather regime - to approximate their 24-hour output. In the tropics, the capacity factor might be 20% - lots of sun, short days, high temps....And of course shading counts.

So with your 3.2Kw of panels maybe you're generating something like 15KWh/24 hours....Compare that with your consumption spreadsheet, and you have the answer....

Sorry if I'm telling you stuff you know....

On our boat we have 840W of panels, and in the tropics that will run everything on the boat except the watermaker. We run engine/alternator/inverter to make water. We have a small token AirCon that only runs at the dock, it's pretty useless anyway.

Thanks for the response & yes, I have the formulation of the energy consumption spreadsheet started, but I was more wondering how many KHW most of you guys' currently cruising are consuming as a daily average on similar type catamarans as a sort of back check for what we are planning on.

I realize it is an impossible question for someone else to answer with any accuracy as there are more variables than could even be listed.

Cheers!

 

[CapDave]

Thanks for the response & yes, I have the formulation of the energy consumption spreadsheet started, but I was more wondering how many KHW most of you guys' currently cruising are consuming as a daily average on similar type catamarans as a sort of back check for what we are planning on.

I realize it is an impossible question for someone else to answer with any accuracy as there are more variables than could even be listed.

Cheers!

What are you sailing?

 

[ol70]

What are you sailing?

Currently OPB's (other people's boats lol), but as I mentioned previously in the thread we are currently having a catamaran built by Nexus/Balance down in South Africa (526MkII). Since it is a semi-custom boat, I'm trying to glean as much knowledge off this crew on the forum to improve upon the build to the extent possible.

There are always nuggets of wisdom to found in the details in threads like this one!

 

[jmh2002]

Don't forget the big question of whether cooking will be gas or electric? It's also relevant when comparing to other boat's consumption figures too.

And as a general note, many cruisers from the past lived quite frugally onboard in terms of consumption, because that is what they were traditionally used to. I also think that just a couple onboard can manage their consumption to be much less too. A family may be quite a different situation.

But on the flip side, some people moving to boats now want to live more like they live in their house. They don't want to hear or care that they can't do this, or that.

Which category do you (or your wife, or family) fit into? How do you live at home?

For example, some people run a washing machine at home every day. For others once a week is sufficient. Same for showers, and women washing their hair (onboard you are both making water as well as heating it - both are big consumers). And what about women using a hair dryer too? Daily, weekly, or only occasionally when going ashore to a restaurant? Do you love to prepare and cook gourmet meals, or is just enough to survive more your style? That will affect the refrigeration, freezer, and cooking consumption numbers too, especially if electric. And will that be to regularly entertain friends from the anchorage, or guests that visit?

So it's the same for a lot of routine things actually. Everyone is different.

But those types of lifestyle related points are relevant to the boat too.

 

[Mambo Kings]

Thanks for the response & yes, I have the formulation of the energy consumption spreadsheet started, but I was more wondering how many KHW most of you guys' currently cruising are consuming as a daily average on similar type catamarans as a sort of back check for what we are planning on.

I realize it is an impossible question for someone else to answer with any accuracy as there are more variables than could even be listed.

Cheers!

This is one of three by Pierre on Marine electrical systems.

I found this table very interesting

 

[CapDave]

This is one of three by Pierre on Marine electrical systems.

I found this table very interesting

View attachment 581275

Putting NMC cathode batteries on a boat is not a good choice, and will very likely render your vessel uninsurable.

I’m about 2/3 of the way through a LiFePO4 upgrade. Lithionics UL listed batteries and dual-channel external BMS, APS Wakespeed regulators - all supplied by Bruce Schwab - wire size upgrades, alternator overhauls and pulley ratio changes, and a minimal monitoring and alarm system. All pre-cleared with my insurance company.

Three main reasons I went with this set of components. The UL listing, the capabilities of the Wakespeed regulators, and above all the dual channel BMS which no other maker provides, though you could kinda hack it with Victron components. And of course the canbus comms between batteries, regulators and BMS is just a different planet than otherwise achievable.

I’ll post more about this system soon.

 

[mpenman]

@ol70 i'll chat briefly about consumption. We're an unusual use case as we normally have 8 folks sucking on the power grid for everything from water to internet, to charging. Our kids are boat schooled so you have 6 of them fighting for desk space and charging outlets.

On our 57 we had 1.2KW of solar and a wind gen. We barely got thru the day on solar and scrimped on water consumption. Heads were salt water with manual flush. LOVED them, easy to fix. Previous owner did a great job with the setup and there was very little parasitic waste of electrons.

Current boat has 5.4KW of solar and we barely get thru the day on solar . This was by design. We have 880amp/hrs @24V of which 750 are usable, after which things shut down to stop me having to bring batteries back from the dead. Not an easy process if your BMS does not want to co-operate, which is normally around 8pm on a Sunday evening following a lively time ashore.

As @jmh2002 & @Capt Dave note, it's about usage. We now have fresh water electric flush heads, which means way more water. We added a dishwasher (love that thing). We use about 50% more water now than our previous boat.

One thing we noted on our previous boat was propane consumption, which was pretty high. We'd go thru a 11lb tank every week, but we have gourmet chefs and bread is baked with abandon. We now have an instahot onboard and absolutely love it. Hot water on demand anytime. Seems like a power hog, but interestingly enough our propane consumption is now about a tank every 6 weeks rather than every week. Much of our propane usage was heating up water for coffee or tea, which is consumed in large quantities onboard. Along with a Instapot, the use for the propane has fell off a cliff. So basically exchanging one energy source for another.

We have Termodinamica 24v AC units. They are 16k btu and can either feed the salon or the two main berths. That is run every evening as the admiral requires AC for sleeping. We do 2 loads of laundry a day (small loads relative to a normal house) and we also run the dishwasher 3-4 times a day. What's interesting is that it uses way less water than 2 under enthusiastic non-paid dishwashers.

So in summary, we store excess energy in the water tanks. When things get tight we load shed. Turn off three of the 4 inverters, turn off the instahot, don't make water, and if things get really tight, no AC for the Admiral.........but we pay for that the next day. We don't have a genset and never use the engines to charge the batteries.

If you are willing to load shed then 2KW is more than sufficient. If most US homes were built and felt that way, you'd be able to remove the power grid!!!

 

[mpenman]

I found this table very interesting

View attachment 581275

I don't agree with that table. Lead Acid's don't last anywhere near as long as LifePO4, and we're not even talking yet about the maintenance required on those things. They don't like being drained less than 50% nor being charged up at high rates. They're old school. Throw them out with the halogen lights!!! So costs are wrong already. Weight, crikey, those things are concrete blocks. Use them for your mooring, but not your battery bank. NMC, ahh NOPE!!!!

Right now the best bang for the buck is LifePO4 batteries with a very good BMS. I have Mastervolt 24/5500 but I have that in conjuction with Czone. I'm looking forward to Dave's write up on his setup. Once he's got his dialed in, I'll copy him

 

[nom de boom]

I agree with @mpenman , that table is somewhat lacking. It confounds chemistry and brand. If you isolate a single variable, say just within the MG Tech products (they happen to offer both NMC and LFP), then it becomes clear that LFP isn't more expensive than NMC, even for the same nominal capacity. At scale LFP is way cheaper (ask the auto industry).

Likewise the gravimetric density difference shouldn't be a factor of two, there are complications with looking at cell vs pack and across different brands, but again MG Tech offer both and the difference is more like 30%.

That table also assumes 80% usable capacities for both lithium chemistries which is fine if you don't care about the NMC system life, but otherwise questionable. LFP are happy to be charged to 100% routinely, take that into account and the density advantage of NMC is even smaller.

 

[socalrider]

Yeah NMC shouldn't really be a candidate for a boat. Surprised to see it in the video. LFP is a great chemistry, I don't see the argument for going with the riskier and more expensive NMC in exchange for a small weight advantage. Good BMS is key though.

 

[Mambo Kings]

I don't agree with that table. Lead Acid's don't last anywhere near as long as LifePO4, and we're not even talking yet about the maintenance required on those things. They don't like being drained less than 50% nor being charged up at high rates. They're old school. Throw them out with the halogen lights!!! So costs are wrong already. Weight, crikey, those things are concrete blocks. Use them for your mooring, but not your battery bank.

Isnt that what he is saying? On battery life, charging and weight lifePO and NMC way out perform Lead Acid. for the same storage a lead acid battery set would way 8.5X the weight....they are in fact impossible for providing the service on a modern Cat

Where he differs from you is that he prefers NMC over LIFiPO

He has made a semi-decent amount of capital from founding the software company that provides the software in several marine BM systems. (Of course if he had realized the potential for electric car engines vs BM systems for marine application, it would be an obscene amount of capital.) I think he is worth listening to for another opinion. He is a humble self depreciating guy.

NMC, ahh NOPE!!!!

Right now the best bang for the buck is LifePO4 batteries with a very good BMS. I have Mastervolt 24/5500 but I have that in conjuction with Czone. I'm looking forward to Dave's write up on his setup. Once he's got his dialed in, I'll copy him

 

[Mambo Kings]

Current boat has 5.4KW of solar and we barely get thru the day on solar .

Good Grief!

We're an unusual use case as we normally have 8 folks sucking on the power grid for everything from water to internet, to charging. Our kids are boat schooled so you have 6 of them fighting for desk space and charging outlets.

I have to agree.

. We now have fresh water electric flush heads, which means way more water. We added a dishwasher (love that thing). We use about 50% more water now than our previous boat.

One thing we noted on our previous boat was propane consumption, which was pretty high. We'd go thru a 11lb tank every week, but we have gourmet chefs and bread is baked with abandon. We now have an instahot onboard and absolutely love it. Hot water on demand anytime. Seems like a power hog, but interestingly enough our propane consumption is now about a tank every 6 weeks rather than every week. Much of our propane usage was heating up water for coffee or tea, which is consumed in large quantities onboard. Along with a Instapot, the use for the propane has fell off a cliff. So basically exchanging one energy source for another.

We have Termodinamica 24v AC units. They are 16k btu and can either feed the salon or the two main berths. That is run every evening as the admiral requires AC for sleeping. We do 2 loads of laundry a day (small loads relative to a normal house) and we also run the dishwasher 3-4 times a day. What's interesting is that it uses way less water than 2 under enthusiastic non-paid dishwashers.

So in summary, we store excess energy in the water tanks. When things get tight we load shed. Turn off three of the 4 inverters, turn off the instahot, don't make water, and if things get really tight, no AC for the Admiral.........but we pay for that the next day. We don't have a genset and never use the engines to charge the batteries.

If you are willing to load shed then 2KW is more than sufficient. If most US homes were built and felt that way, you'd be able to remove the power grid!!!

Sounds like the Admiral wrote the spec' and your job was to execute. I admire that you succeeded in meeting spec totally on Solar without a generator.

 

[Dogfish]

It's a complete minefield. I probably am the other extreme we suvive with 258watts of solar in the UK. No other means of generating power, fridge on 24/7 well insulated. 6 x 43 watt panels much better than a couple of large panels when it comes to shading, mounted on top of the cabin. Cook on gas. Going up to 10 x 43 watts and adding a freezer and maybe a induction hob. Often arrive after a passage with full batteries if it's sunny. But as the guy's say pretty dependant on the type of person you are, everything is pretty power effecient so I can relax with a cold beer.

 

[nom de boom]

I think he is worth listening to for another opinion. He is a humble self depreciating guy.

I took the time to watch the video and I agree with you on this.

I still think that his comparison is flawed though for the reasons I stated above.

LFP has gained a huge amount of market share in the 2.5 years since this video came out. It would be interesting to hear how he's changed his view since.

 

[mpenman]

Isnt that what he is saying? On battery life, charging and weight lifePO and NMC way out perform Lead Acid. for the same storage a lead acid battery set would way 8.5X the weight....they are in fact impossible for providing the service on a modern Cat

Where he differs from you is that he prefers NMC over LIFiPO

He has made a semi-decent amount of capital from founding the software company that provides the software in several marine BM systems. (Of course if he had realized the potential for electric car engines vs BM systems for marine application, it would be an obscene amount of capital.) I think he is worth listening to for another opinion. He is a humble self depreciating guy.

Point well taken.

I'll review the video. Did not take the time to do so.

 

[ol70]

@ol70 i'll chat briefly about consumption. We're an unusual use case as we normally have 8 folks sucking on the power grid for everything from water to internet, to charging. Our kids are boat schooled so you have 6 of them fighting for desk space and charging outlets.

On our 57 we had 1.2KW of solar and a wind gen. We barely got thru the day on solar and scrimped on water consumption. Heads were salt water with manual flush. LOVED them, easy to fix. Previous owner did a great job with the setup and there was very little parasitic waste of electrons.

Current boat has 5.4KW of solar and we barely get thru the day on solar . This was by design. We have 880amp/hrs @24V of which 750 are usable, after which things shut down to stop me having to bring batteries back from the dead. Not an easy process if your BMS does not want to co-operate, which is normally around 8pm on a Sunday evening following a lively time ashore.

As @jmh2002 & @Capt Dave note, it's about usage. We now have fresh water electric flush heads, which means way more water. We added a dishwasher (love that thing). We use about 50% more water now than our previous boat.

One thing we noted on our previous boat was propane consumption, which was pretty high. We'd go thru a 11lb tank every week, but we have gourmet chefs and bread is baked with abandon. We now have an instahot onboard and absolutely love it. Hot water on demand anytime. Seems like a power hog, but interestingly enough our propane consumption is now about a tank every 6 weeks rather than every week. Much of our propane usage was heating up water for coffee or tea, which is consumed in large quantities onboard. Along with a Instapot, the use for the propane has fell off a cliff. So basically exchanging one energy source for another.

We have Termodinamica 24v AC units. They are 16k btu and can either feed the salon or the two main berths. That is run every evening as the admiral requires AC for sleeping. We do 2 loads of laundry a day (small loads relative to a normal house) and we also run the dishwasher 3-4 times a day. What's interesting is that it uses way less water than 2 under enthusiastic non-paid dishwashers.

So in summary, we store excess energy in the water tanks. When things get tight we load shed. Turn off three of the 4 inverters, turn off the instahot, don't make water, and if things get really tight, no AC for the Admiral.........but we pay for that the next day. We don't have a genset and never use the engines to charge the batteries.

If you are willing to load shed then 2KW is more than sufficient. If most US homes were built and felt that way, you'd be able to remove the power grid!!!

Wow, 5.4kW of solar is pretty impressive. This feedback is definitely helpful, so thank you for sharing! We will have all induction cooking, and a few other things drawing a bit more power, but we will most of the time be 2 people, so on the surface I think we will also not need additional power generation. I'll definitely report back once I have some real-world experience with the systems.

 

[CapDave]

Where he differs from you is that he prefers NMC over LIFiPO

To get in the weeds for a moment, NMC is a metal oxide, FePO4 is a metal phosphate. The oxygen in the phosphate is more tightly bound in the molecule than the oxygen in the oxide. And, FePO4 runs at a somewhat lower voltage than NMC. This dings the energy density, but....

The volatile organic electrolyte that is substantially the same in both chemistries is quite sensitive to voltage and temperature. The threshold of spontaneous combustion is much closer at NMC voltage. Charge/discharge them hard, especially in high ambient temperatures and it starts getting a little scary. Then add shock, vibration, impact, etc, and the chance for a mechanical short rises - which drives temperature and can even provide an actual spark.

Over 100C the electrolyte starts degrading, at 140C the electrolyte degradation accelerates rapidly leading to spontaneous combustion, and the NMC metal oxide gives up its oxygen to fuel that. In the parlance, it's "rapid oxidation accompanied by spontaneous disassembly" In English that's fire and explosion. And nearly impossible to extinguish with the materials themselves providing the oxidant.

Every study I've seen, all the data I've seen, backs this up in multiple different scenarios. The tipping point is that NMC burns so hot with all the oxygen the oxide surrenders at lower temperatures that thermal runaway is nearly inevitable, and the entire battery pack then burns at very high temperatures. Like burn a hole through the bottom of your boat temperatures. With FePO4, most of the time the pack doesn't go into thermal runaway, and the event is local, a cell or a couple cells smoke or burn but don't drive thermal runaway, and the boat will survive it.

For me the ~20% bump in energy density isn't worth the risk. And with LiFePO4 I get two of the biggest benefits of the upgrade from PbA anyway - indifference to Partial State of Charge, and full Charge Acceptance across the entire range of State of Charge. Those are very valuable properties.

 

[CapDave]

made a semi-decent amount of capital from founding the software company that provides the software in several marine BM systems. (Of course if he had realized the potential for electric car engines vs BM systems for marine application, it would be an obscene amount of capital.)

Actually he probably would have made nothing; automotive BMS was (and is) a heavily competed space with scores or more of startups not to mention incumbents' own internal programs. The BMS systems that won were those strongly tied to the incumbent battery and auto OEMs that were either in house projects or startups that got bought (very) early. There's a few smaller independent electrification players around still alive, but mostly struggling.