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Comment by gabereiser | Hacker News Reader

This is awesome. I lived on a sailboat for a while and sometimes you get cloudy weather for days, blocking your ability to use solar to top up your batteries. The small M35 universal diesel engine I had had one thing going for it, it had a lot of torque. Torque I use to turn a 110V 120A alternator. The alternator (like a car’s) charges the battery, except in my case it was charging a lot of battery. 6 12V 200AH Lithium Iron batteries. These batteries ran all the “home” appliances for several days before needing a recharge. 120V 3000W inverter, A/C, Fridge, coffee maker, water maker, electric stovetop, lights, navigation, radio, Starlink, Xbox.

If having a vehicle is unsightly, you can remove the engine onto a stand and wire it up exactly as described in this video. The only thing you’d need to run an engine is a fuel line, a spark, and compression.

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You also need a cooling system to run nearly all engines. Generally a car engine doesn't have enough cooling system to run at max power for very long (it is only a few seconds between the light turning green and you being at speed, then you need much less power). Your sailboat as the nearly infinite ocean to cool itself with.

Most likely your engine also needs a computer, which implies an electrical system.

Living on a sailboat, the cool water would not be a problem. Just some filters to avoid clogging the cooling ducts.

> Most likely your engine also needs a computer, which implies an electrical system.

Old diesel clunkers not really, at least if you don't care about emissions control. Fuel injection / exhaust valve control is purely mechanical, all they need electricity for is the engine starter and, depending on age, the cooling fan.

Modern engines, on the other hand, these can be really hard to run on their own outside of a car, at least from hearsay - I only have had experience with an 1994 VW T4 van.

I've tried with Opel from 2004. I had a very modern version (with everything over CAN, even gas pedal) and I had to disconnect A LOT of sensors in order for it to no longer start (don't ask why). Modern diesel cars are a little worse for this, because of all the emissions regulations requiring adblue and dpf filters to work correctly. If you run out of adblue in some cars, you have to get it towed to dealer for checkup and reset.

>all they need electricity for is the engine starter and, depending on age, the cooling fan.

If you get an old enough diesel engine or can do the mod yourself you don't even need an electric starter. The first diesel engine I worked on used a gasoline engine as a "pony motor" to spin the diesel engine flywheel enough to generate the compression needed to start the diesel engine. From memory (probably wrong haha) you cranked the gasoline engine and brought it up to high rpm and then you started the diesel engine using a lever that gradually engaged the diesel engine flywheel bringing it up to operating speed. Once the diesel engine was running you backed off the lever and killed the gasoline engine.

An obvious disadvantage would be the necessity to maintain stocks of two fuel types. Other than that it is a near fool-proof way to handle cranking a diesel engine. The electric starter is replaced by the gasoline engine and flywheel linkage. You effectively roll-start the diesel using the gasoline engine.

Video of this in action:

https://youtu.be/AL0ls_UpT8w?t=361

The whole video is worth a watch, but I linked directly to the timestamp where he begins to explain how the engines are started with a petrol starter. To power a foghorn. Amazing stuff.

Yeah that is amazing and it is just like the engines we had on those post-WWII bulldozers and maintainers. Fire up the gasoline engine and get it screaming at high rpm and then use that high rpm to transfer power to the flywheel of the diesel engine which will crank and run once the compression is high enough to ignite the diesel.

Here is a video of a guy cranking a Caterpillar D2 like we had to crank our D4 back in the day. [0]

When I started working with that small family-owned company I had no real experience with mechanical things other than my own pickup truck. When I finally moved on from them a couple years later I could maintain, tear down, and rebuild gasoline and diesel engines, compressors, hydraulics, air brakes, etc. We did all of that ourselves in addition to the real jobs of pipeline maintenance and repair and oil spill cleanup. I don't remember all the times I spent laying on the dirt floor of the "shop" there in central Texas and cursing all the oily sand and crap that fell in our eyes and faces as we tried to fix things after the day's work was done. Luckily beer-thirty was a cherished event that came with hang-down (summer sausage), cheddar cheese chunks, fresh onion slices, cold milk and saltine crackers. We finished most days in the domino shack trying to avenge the previous days' losses. Good times indeed.

[0]https://www.youtube.com/watch?v=Ck210eL9qcI

> An obvious disadvantage would be the necessity to maintain stocks of two fuel types.

Wouldn’t a starter motor running off a battery charged by the very generator you are running just be an all around better solution? You can run some modern starter motors off a tiny 12x8 in AGM.

That may be true if you are building this today. There evidently were enough problems with that setup back when these pony motors were common to make the use of a pony motor instead of battery power more practical. Perhaps it was a battery efficiency issue or one where a battery couldn't supply enough amperage to generate the torque required for a standard starter to cause the diesel engine to start and run. I know that a pony motor starter was standard on old heavy equipment diesel engines until the late 1940's and possibly after that.

That’s true and there certainly other considerations. I know which I’d consider to be a more solid/reliable option if I were going to be somewhere without access to electricity, at least. It’s easy to see when you’re running low on gasoline and when you’ll need to top off, but I wouldn’t want to be relying on a small 12v battery if I didn’t have a backup jump source available.

That's true. For backup power on my own property I bought a used towable light tower/generator with an industrial Caterpilalr diesel engine and a 20 kW generator. It is portable, comes with its own lights, has a large capacity fuel tank so it can run for days, and it generates enough power to power my house and my shop should I lose grid power. Since it is portable I don't need to rebuild my old gasoline welder to use working on my fence since I can power my electric welder directly from the unit. It also has enough outlets to run several electric tools simultaneously.

I have to add a frequency meter on the generator so that I can make sure I get some clean power and a power conditioner to smooth all the wrinkles so my electronics inside the house won't be damaged. Then I need to have an electrician add the subpanel and manual or automatic power transfer switch but for the price I paid it is a bargain over the usual generator packages available.

That sounds like the making of a great setup! I likewise far prefer to purchase used industrial equipment instead of new residential-grade stuff. But as much as I’d love to be in your kind of environment, we’re in a more suburban setting at least for the medium term - where I’m blessed to have piped natural gas, though. I haven’t bit the bullet yet, but the convenience of a NG generator in that setting is hard to compete with.

I promise I would already have a NG generator if I had gas to the property. I have a high pressure pipeline easement across my place now but there is no way to tie in or buy a drop to supply anything here. It is a gathering system and not distribution I guess. Propane is doable but we decided to focus on solar for those things that aren't easily tied to the existing grid power and this portable generator for its high utility value out here. Good luck to you!

I think everyone here is underestimating power density of a car engine. GP's alternator is 110V/120A, that's 13.2kW, or up to 8-way tea kettle boiling or Xeon workstation use simultaneously(1.5kW each).

Chances are you won't be running 4 YouTuber editing machines, 2 pots cooking on IH stoves, 2 air conditioners and a USB-PD laptop charger all drawing full amount inside the living quarter on a sailboat. That's before counting in 6x 12V/200Ah = 14.4kWh battery system which safely doubles, possibly quadruple instantaneous draw.

Most household requirements are about 13kW. So not much different than your suburban bungalow needs.

I think there's something wrong with your palace if you're maxing out 100A breakers, that's 720[hr] x 13[kWh] x 0.30[$/kWh] = $2.8k/month. Even if you meant 1/3 duty it's $936/month.

Average household usage in US is 20-40kWh/day... not sure where does 13kW figure fits in that picture.

they missed a decimal point. Average US household consumption over a year is approx 1.25KW.

200A service is standard transformer to a house.

Constant 50% utilization is not!

We both understand that the service has to support the max load, right? The average is less than worthless for calculating capacity of circuit breakers etc.

Wouldn't it make more sense to install 230V on a boat? Modern electronics handle 100-240 anyway and you can save on cables.

Boats are typically so small that you can use smaller cables without problem even at 120 volts. Many of them run only 12 volts (often most things like lights and radios are run on 12 volts, but the owner as an inverter for a couple appliances they can't find in 12 volt). Of course nobody runs smaller cables at 120 volts because you would need an engineer to figure out the proper rating - it is cheaper to just use the standard code wires. If you do pay an engineer you will probably discover on boats you need to use the larger wires anyway for mechanical reasons.

Having wired up a couple travel trailers and a boat (and, incidentally, being an EE who can theoretically run those calcs), I agree with the parent: It would be better if the industry switched to 120V/220V AC for more parts, and away from 12V.

The problem is that the ampacity in a 12V DC light circuit is 10x that of an equivalent-power 120V AC system. And worse yet, power dissipation in a resistive element is equal to I^2 R, so you're heating the wiring harness with power losses are 100x worse than in a 120V system and almost 200x worse than a 220V system. So you have to oversize the wires to reduce R, which adds weight and cost. And if you drop 2V to line losses in your 12V system, your device is seeing 83% of the nominal voltage, while if you drop 2V in a 120V system (you won't, because Ohm says voltage drop is equal to IR, and I is 1/10th that of a 12V system), but still, you're 98% nominal.

They're running 12V because that's the voltage of a classic 6-cell lead-acid battery, and you probably didn't want 220V in your Model T, even with felted asbestos insulation, but I'd be confident enough to lick a modern XLPE wire carrying 220V. A century of using those lead acid batteries (and worse, 3-cell 6V systems...can't endorse converting your classic car to 12V enough...) created now-entrenched economies of scale for lamps, and switches, and pumps, and radios, and fans, and most of the other things you need in a boat or camper. The only advantage of using those 12V parts is that their manufacturers put a little more effort into making them efficient. No one (sadly) will notice or care if the AC-DC converter that runs the clock on your stove burns 5W at idle even though your wall clock can run on one AA battery for years, but they will notice and care if their camper battery is dead after leaving it parked for a couple weeks.

Today, I recommend using LiFePO4 batteries in whatever series cell arrangement gets you the required watt hours, regardless of that output voltage. Then run a modern, high-efficiency (high-frequency) digital inverter to bump the voltage up to whatever your local AC grid runs at. You can go 220V AC in the US if you really want more efficiency and smaller wires, and are willing to deal with the hassle of finding the right lightbulbs and international power cords and so on.

Doesn't a 48V DC installation provide a very reasonable compromise?

That's what I use for my off-grid solar installations, and it works pretty well. 4x less amps, and you still get a safe voltage.

Yes, but there aren't many 48V DC appliances -- radios, lights, gauges, etc.

Many larger boats have 24V DC systems, and there are quite a few boat electronics that run on either 12V or 24V (though you will still need either a 24->12v converter for many things, or be able to tap 12v from the battery bank).

DC-DC buck converters got incredibly cheap and efficient, every small appliance can have one.

Yep, that's a great compromise. 40V, 56V, 80V, 48V outdoor power tools use the same voltage for many of the same reason (they're slowly moving away from 18V battery packs for anything high-power). Maybe after a few decades, RV suppliers will standardize on 48V DC lighting circuits, a standard 48V DC receptacle, and provide fans and smoke detectors and pumps and sensors and so on that run on 48V DC. Integrated circuits will emerge in quantity designed to rectify 48V down to whatever the LED drivers and microcontrollers and so on use, and eventually compete in economies of scale with those used in the 12V automotive world.

But good luck finding those parts today.

I would think 110v would be a little bit safer in the wet environment. Not perfectly safe but better.

12VDC is the standard on boats, campervans, RVs, etc because it can be delivered straight from the batteries. In order to deliver 240/120VAC you'd need an inverter to generate the signal, and this obviously introduces loss during conversion. For cable runs through the length of my boat (52ft), the cables aren't particularly thick - the thickest cables are in the engine bay, going from the alternator on the diesel engine to the batts, and again from the Solar controller (MPPT) to the batts.

There's a plethora of stuff you can use with 12VDC to the extent that the only things I run off 240VAC is the vacuum cleaner and the TV (12VDC TVs are available but the cost vs quality payoff isn't really worth it).

230VAC flat screen TVs tend to be powered by 14VDC at the motherboard level, might well function if fed 12VDC from an external power source, bypassing the built-in step-down converter entirely.

Typically you don't want lethal potential in such wet environments. Ever wondered why emergency lights on ferries are different than the standard ones? Also, you don't want any earth breaker since you really want the lights, pump and motor to be working no matter how much water you have on the wrong side of the hull.

If you go diesel, you remove the need for spark, but perhaps starting is a greater challenge.

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