Simple vs complex energy systems on board

[rslifkin]

I often see generators over-sized to be able to run every last thing on the boat at the same time. In many cases, actually doing that is pretty rare. I'd much rather see a generator sized to a realistic load scenario. Over-sized generators are much more likely to suffer from issues relating to under-loading, or require you to effectively waste power (and therefore increase fuel consumption) to keep them from running too lightly loaded much of the time.

Needing to run large amounts of air conditioning away from shore power is the biggest use case that still needs a generator. Personally, I'd rather avoid the fuel, noise, fumes, and maintenance most of the time, so outside of a few high power draw tasks and occasional really hot weather where we can't just go somewhere to plug in, we try to run the generator as little as possible.

 

[cfr]

confirming.....after spending 8 years in greece with 35 degrees on land but beeing allways at anchor we missed aircon maybe 10 nights per summer, but we have a good ventilation. one hour in the evening while cooking it would have been nice. instead of my 25 year 12 kw i would prefer a 6 kw. but the exchange is complicated, selling the old difficult etc so i run him until he is dead

 

[SteveK]

In residential apartments generators were used to run emergency lighting. They worked great until they did not. However, there were no replacements for small generators as one size fits all was adopted.
Perhaps this occurred in boats as well.

I know with my 8kw GEN I plan ahead to load it up most of the time.

 

[mydacha]

I decided to add a separate isolated AC system based on a 48VDC architecture, in addition to the existing 12VDC–220VAC setup.
The system includes a 9 kW genset, 1.2 kW solar panels, a 600 Ah 48 V LiFePO₄ battery bank, and 280 Ah 12 V lead-acid batteries. The port engine has a 12 VDC 5 kW alternator, and the starboard engine has a 48 VDC 6.8 kW alternator.


All systems are isolated and can operate independently, powering different AC load groups such as air conditioners, heaters, washing machines, watermakers, grills, icemakers, and fridges.
At idle, the main consumers are the fridges, Starlink, CCTV cameras, and dehumidifiers.

It all sounds complex, but once the system is isolated into separate circuits and interacts only through AC, everything becomes much simpler.

 

[O C Diver]

another question....my genny will have 12 kw which is a lot, so i need to consume 8 kw to run it ....why they are so big. so need to charge 2 kw to batteries 2 kw to bake bread run the washing machine and cook on the induction cooker......i would need a electric sauna to use so much available power.

One concept for sizing is to size it for your shorepower connection. 12 KW is 240 volts at 50 amps. I'm assuming that's what your shorepower service is.

You don't need to run it at 2/3 of maximum load. The objective is to get it up to operating temperature and cook the moisture out of the oil. What you don't want to do is to run it for short periods where it doesn't reach operating temperature. Basically, run it for atleast an hour.

Do a load of laundry.
Recharge the house bank
Run the water heater.
Cook dinner

The above will easily get the generator up to operating temperature and should provide over an hour of use. If you're really worried about it, plug in two 1,500 watt heaters (on seperate circuits) on the back deck, that will give you 3 KW of additional load. IMO, load it up in the beginning to cook the oil, then try to keep it around 2 to 3 KW. What you don't want to do is let it run below operating temperature or below 2 KW for hours.

Ted

 

[Jeff F]

a refreshing guy when we all want to maximise energy use......

I don't think it's about energy use for most on this forum.

If you don't have AC your total energy consumption for house needs will be small. Let's guess at 10 kwh per day. You can generate that by burning 4l of fuel.

That certainly adds up if you're anchored for weeks at a time without moving. But if you're travelling regularly it's not going to be noticeable at fill-up time.

I have solar and love it. I leave my boat moored and unattended quite often, and solar keeps my fridge, anchor light and internet connection up and running indefinitely when combined with a big battery bank. That's a big plus for me. The other big plus is minimizing noise from the genset. I'm writing this from a quiet anchorage where I've been for the last day or so without running an engine.

There's a lot to be said for using what you've got, but I'm not sure the skepticism on solar is warranted. It's not all or nothing. And who is arguing that small battery banks are better than big ones? Whether there's a payback for change depends on your individual use case and preferences/goals, and appetite for change.

 

[READY]

Beeing new to this power hungry boats with fridge freezer etc i was hoping that one can run the 1 or 2 hrs a day, never thought about running it 24 hrs. My genny is also too big with 12 kw....after a season i might know better how the average consumption is. Or do you have somefigures at hand ? Isnt a 1000 a 12v house bank enough for 12 hts and can be charged in an hour or does one need lifepo for this fast charging, i have zwo victron combi 12 120 3000

Yes you need LFP for fast charging. AGMs or lead acid have a much lower charge acceptance rate vs. LFP.

But there are limits based upon charger, wiring and battery as to how fast you can charge LFP.. With your dual Victrons you are maxed at 240 Amps/hour so if you drain a 1000 amp LFP bank you need about 4-5 hours to charge them back to 100%.
Ken

 

[Fish53]

I have two group 31 12 volt batteries, a battery switch and an alternator on my engine.

 

[cfr]

as we will cook and bake at least once a day this can be combined with some charging. but i will look for a slim solar bimini. luckily charger and genny are there and running so its not urgent to change......

 

[Bmarler]

Solar will really help. I have 1125 amp hr bank of agm and two solar panels on the pilothouse roof. I rarely run my genset. I don’t have electric cooking though. On the rare occasion that I need to run the genset to charge batteries I put a bulk charge in for an hour or two, then let the solar finish.
I typically use 30% of my battery capacity in 24 hrs. with no charging happening.

 

[Frosty]

As I'm sure you can tell above, I'm a fan of solar. Since I don't have big usage items most of the time, it basically provides all my recharging. If there is a string of cloudy days, I can get through around 4 days just on battery power, and then if I get underway I can turn on the engine charging.

But that aside (just figured it was fair to say where I'm coming from), I think the "ugliness" of solar panels -- to my mind -- is tempered by their utility and blessed silence. They also never need fuel, oil changes, or much in the way of spare parts carried along.

But I think it must be something like deck railings. Sure, every boat might look better without them in theory; but I like to see a boat with good, sturdy railings/bulwarks because I know how useful they are. So their looks improve, in my mind, based on that function. Same with an anchor on a beefy roller (I guess the boat itself would look better without one), etc. Their lack of ugliness is inversely proportional to what I know they can do.

(Of course you can still have a better- or worse-looking installation of any of these things depending on how you go about it.)

That said, @cfr , your boat has gorgeous lines, so of course you will want to think about that if/when you add solar. But apropos of that, you don't have to add a ginormous array that will do it all to get any benefit. Even if it just silently helps you along with some of your re-charging, I think it's worth it.

 

[rslifkin]

I agree that solar is well worth it. Having power just appear without having to think about it is incredibly convenient even if it doesn't cover your whole power budget.

 

[Bmarler]

completely agree. solar doesn't cover everything i need unless it's a bright day in the middle of the summer. but, even in winter it helps stretch out the time between engines running.

 

[cfr]

yes to keep batteries happy its nice. on my sailboat i have trojan batteries and k leave the boat 6 month in sunny italy and they charge some a every day and keep them happy. ill find some place, maybe i toss two in the dinghy, better then nothing.

 

[Delta Riverat]

I like my solar too. I was able to install it so that the only clue it's there is a couple of wires on the port fly Bimini. Can't see the panels at all.

 

[ABfish]

I can't run my air conditioner without the generator. If generator fails, I can charge my house bank with my port engine. Charging with the engine gives me the same redundancy as solar.

I can run the gennie overnight to run A/C (wife can't sleep without it) and fully charge my house bank, heat water, run the electric grill, etc. I've not added propane to the boat as we've come to appreciate the Kenyon electric grill.

If I anchored out a lot, I might feel differently, but for my use case solar is one more system to learn and monitor with minimal benefit. I reached the same conclusion about adding a propane cooktop in the galley.

Count me in the "keep it simple" and "use what you've got" camp.

 

[tiltrider1]

This is another 1 vs 2 engine discussion. My generator is pretty quiet. If the tv is on I can’t even hear it. My maintenance is pretty non existent, oil change once a year and an impeller every 5 years. In the summer it might run 4 hours a day to make water, heat water and charge batteries in the winter it might run 12 hours a day just to heat the boat.

Don’t care if solar panels would get me by with less genny time. Don’t care if solar panels would cost me more or save me more. I’m happy and if it’s not broke I am not going to fix it.

Now if a generator is an issue for you and solar solves the problem then great, you have a solution. Everyone has different issues and different solutions. Adding Complexity for no gain makes no sense to me but some times what others think of as complex I think of as simple.

 

[Frosty]

Now if a generator is an issue for you and solar solves the problem then great, you have a solution. Everyone has different issues and different solutions. Adding Complexity for no gain makes no sense to me but some times what others think of as complex I think of as simple.

Or, in the same vein but opposite, a person might have solar and a well-sized battery bank; so for them adding a generator would be the more complex route.

Seems like the friend of the OP figured "everyone" has a generator and so adding the so-called "ugly" solar panels and better battery bank was complex and running a generator, simple; but as you said, it's much more variable than that and depends on the boat setup -- and the boater.

 

[Ithaka7]

I would say you have critical systems that need to be simple and redundant. For me this is the starting battery, engine controls, the anchor system. Separate and independent for each engine. Everything else is a matter of interest in tinkering, age and familiarity with technology. If it pleases you, go ahead. I also like the idea of replacing the bimini with solar panels... it is actually cheaper than a new bimini and it can be made to look good! Amazing.

 

[LargeMarge]

... there are alleays compromisses

.
Screenshot, cropped, added to screensaver rotation.

 

[Lepke]

Previous owner of my boat ran a generator 24/7. There are 2 generators, both had glazed cylinders from running to much on light loads. I put in an 48v inverter an an inverter bank that lets me have power for about 3 days unless I have a lot of people on board. I added 48v alternators on my twins.
Running I never need a generator, the bank stays charged. At anchor, about every 2-3 days I run a generator, charge the bank, do laundry, make water, turn on the water heater, etc. My hot water tank is super insulated, and stays hot several days. I have a diesel stove so I don't have to run a generator to cook.
With a properly sized inverter, and the ability to charge while running, I almost don't need a generator. If I want, I can make water or do laundry while running. I use 8d batteries because I don't trust batteries that have a reputation for catching fire.

 

[Mambo42]

I use 8d batteries because I don't trust batteries that have a reputation for catching fire.

Which batteries have a reputation for catching fire ? Am kind of curious if i missed something.

 

[OldDan1943]

always think of the next owner. Try to keep it simple, easy to understand and maintain.
You can have high capacity inverter but you need lots of battery capacity to support it.
I am 82 years old and I hate 8D batteries

 

[Frosty]

Which batteries have a reputation for catching fire ? Am kind of curious if i missed something.

I'm guessing he means lithium (Concorde, etc.). IOW, lithium types which I've not heard of anyone using on boats. But sometimes people presume all lithium containing batteries are the same -- so maybe that's what happened.

BTW, @Lepke, I've never seen your boat, but it sounds pretty cool!

 

[Lepke]

When I buy 8d batteries, they come with a couple gorillas. I replace all, including starting batteries at the same time and get a better price. I'm too old to lift 8d batteries. I have 3 banks of 48v and a starting bank of 4.

 

[Rigamarole]

I came from a sailing background where over the ownership period I made the boat totally self sufficient down to making water. The only thing I couldn't run off the solar array was the a/c.

With my new (old) LRC I'll have to simply modify the expectations. I absolutely hate the sound of a generator running, even if it has the drystack exhaust. We have two generators, a 13kva and 26kva and a 3000 watt 120v inverter/charger. There are 12 8D batteries for the house bank.

What we will probably work towards is installing an automatic generator start system and an 8000 watt 230v inverter. Right now the inverter would mostly be sized to charge the house bank quicker. When the existing house bank gets older and doesn't hold a charge overnight, we'll upgrade to lithium. Then the small generator would run at about 60% load to recharge the bank and we can use the stove/oven off the house bank inverter.

After this is set up I'll probably look at some of the portable a/c options out there so we can at least cool two of the berths without running the whole boat a/c system - which draws about 32 amps / 230v. It's unlikely solar will make sense due to the high power consumption of the boat, the fact it already has two generators, and that we would be cruising in areas without high sun days (PNW). And, the fact of the matter is with my sailboat we spent 95% of our nights at anchor and with the power boat it's going to be 50/50 (I hope).

For the A/C it would be something like this where we can just take the exhaust hose and put it out our side port. Super small, inexpensive, easy, and very low power draw.

Amazon.com

 

[rslifkin]

It's unlikely solar will make sense due to the high power consumption of the boat

Even if it only cuts down generator runtime some it might make sense. But it's also a question of how much solar you can fit.

 

[hollywood8118]

This is a great thread, I too am trying to figure out the best option on our new boat. The previous owners had no solar aboard, they obviously ran the genset for ac and power needs. I have started to collect solar to add to the two bimini tops with separate controllers for each section,roughly 1200 watts total. One will be the latest generation of flexible panels, the second will be an array of hard panels. The boat just had new bimini's in the last few months. I probably should have just had them hold off on the aft bimini and just modded the frames to accept the hard panels.. live and learn. The battery banks are 8d AGM units under 3 yrs old. For now the plan is run them until the die.. then i guess do lifepo replacements. Planning to keep the start and thruster/hydraulic crane banks as lead acid. Just now I am trying to wrap my head around the tech on how I will charge charge the LFP units with the alternator(s) and keep all the chemistries happy. I doubt the main inverter/charger has the correct charge profile to deal with LFP so that is another issue. The boat is fairly power hungry (although I haven't spent a night on the hook yet to see how hungry) with a pair of 120v house refer/freezer units, 3 zone ac for winter/summer comfort, starlink etc. I plan to add a typical diesel air heater to augment the heating as they are pretty energy efficient on the hook.. and I already had a new unit I hadn't installed on the last boat. One thing seem to have a hard time understanding is Dc to DC charging some people do to be able to mix the chemistries together and keep the alternator happy, they seem like such minimal amp charging units that negate the massive charge rate profiles is a big benefit of LFP banks.. more homework needed I guess.
Hollywood

 

[Rigamarole]

This is a great thread, I agree!

Planning to keep the start and thruster/hydraulic crane banks as lead acid. Just now I am trying to wrap my head around the tech on how I will charge charge the LFP units with the alternator(s) and keep all the chemistries happy. My understanding is you need to use a battery to battery inverter. IMO it really is like a drop in the charging bucket though. I'd rather go to a super high amp output inverter/charger off my generators and just get the house bank recharged. I doubt the main inverter/charger has the correct charge profile to deal with LFP so that is another issue. The boat is fairly power hungry (although I haven't spent a night on the hook yet to see how hungry) with a pair of 120v house refer/freezer units, 3 zone ac for winter/summer comfort, starlink etc. I plan to add a typical diesel air heater to augment the heating as they are pretty energy efficient on the hook.. and I already had a new unit I hadn't installed on the last boat. One thing seem to have a hard time understanding is Dc to DC charging some people do to be able to mix the chemistries together and keep the alternator happy, they seem like such minimal amp charging units that negate the massive charge rate profiles is a big benefit of LFP banks.. more homework needed I guess.
Hollywood

Your situation is similar to mine. I look at it like I'd rather invest in the inverter/chargers than mess with a lot of other inter-connected systems. Like really I could install two 24 volt Victron 5000 watt 230v Quattro's and have 240 amps charging into the house bank. That's a poop load of recharge and would match up with my small generator KVA perfectly.

 

[Fletcher500]

When we had a new build going on in 2017-2018, AGM was the standard and I believe LiFePO4 was just coming on line so I went with a large AGM bank.

We have moderately sized solar panels on the Bimini (Solbian Flat panels) which have held up well and still producing their same yield, but I remove the Bim and panels for the winter and don't install until the spring.

Our use case is longer travel distances (12 plus hours), but then anchoring or mooring for multiple weeks without plugging in to shore power. We therefore don't have a lot of opportunity for alternator charging every few days that often occurs with PNW and East Coast cruising where there are nearby travel destinations and the boat is being run often.

We also go through A LOT of water, mainly due to showers on the swim step for water sports, in and out of the ocean all day. When my kids and their significant others are on board, it can be 75 + gals of water for showers alone in one day.

When I was looking at stabilization options and traveling in the Channel Islands with lots of kelp and carpet bombing lobster pots staring in the fall, I wanted to avoid external protrusions on the hull which led to me to an internal Gyro - SK5 which requires a Gen.

I therefore decided to go with a larger Gen (9KW) for the above loads. I have no problem loading it properly and drawing 50-60A. For multi week trips and just my wife and I with no shore power, I turn off all non essentials and we operate like a sailboat. In this mode, I can get by with 1.5 hrs of Gen run time per day which is low impact and very minimal fuel.

If I were doing it all over in 2025/2026, LiFePO4 for sure, but I would also have a Gen.

Everyone's use case is different, but for us, this set up has worked out well.