Replacing diesel with electric

[skipmac]

Originally Posted by Screwdiver

The motor is from a small shop specialized in converting boats and cars and it is of the automotive variety.. The motor itself is pretty standard, it is the control unit that contains the magic ;-). My idea was: I didn't want to buy components, i wanted a system with charger, motor and control unit incl. joystick. This came for roughly 4500 Euro, i added 1500 for the genset, 1000 Euro for batteries and again 1000 for welding and so on. All in all this was the same price as a cheap marine diesel.

For my use case it is next to perfect. Ample power for very short usage.

As so often in electrics the problem is with the energy lost as heat. You need to think about cooling. I took with air cooling, as i could readily shape an airflow through the engine room. Ironically it is the control unit that produces most of the heat.

This illustrates one of the objections I have to "marine" electric propulsion systems. In the US systems (motor, controller, cables, no charger) I see small 5 kW systems sell for €5000-€8000. 12-16 kW systems well can be €15,000.

I know these are small volume products, not like auto electric systems that make hundreds of thousands of units, but still, one major barrier to marine electric is price. Until the suppliers and manufacturers get real on price electric will be a very small niche.

[rosatte]

wait till ur 50 miles from ur destination and theres no wind for 3 days u.ll be glad u have a diesel because no electric motors gonna take you that far..

[keith4001r]

Originally Posted by rosatte

wait till ur 50 miles from ur destination and theres no wind for 3 days u.ll be glad u have a diesel because no electric motors gonna take you that far..

Thanks, most helpful response yet.

[GrowleyMonster]

I went electric. If you like to tinker with stuff, you can get your foot in the door for less than a third of what a new Beta 10 diesel in the crate will cost. A turnkey system will cost a good bit more, but all the engineering is already done for you. There is a yahoo group for electric boats that you might want to check out. https://groups.yahoo.com/neo/groups/electricboats/info to join. My own (ongoing) electrification oddysey can mostly be found at http://www.growleymonster.com/eboat/ and it needs a lot of updates as I have done stuff that I have not documented yet on the site.

Electric is IDEAL if you only need mechanical propulsion for short distances. It CAN be cheap to install. A kw/hr of shore electricity into the battery charger costs an average of 12 cents. Diesel? You do the math. Diesel fuel is very energy dense. It also costs considerably more per actual kw/hr of work done, even so. With electric there is no more fuel smell. No more fuel pumping. No more fuel leaks. No spills or fines. WAY less noise. Instant power, no warmup. Simple mechanics. All the magic is inside the controller, a "black box" (usually aluminum actually) with a bunch of wires and lugs for attaching cables.

With electric you can go pretty far. You can go fairly fast. You can get by with a fairly small battery bank. Unfortunately you got to pick just one of the above and compromise on the other two. You can't have all three or even just two. Me, I don't mind going slow, or having a big heavy bank. My conversion from Atomic 4 to electric cost as I recall just under $2500 including my eight 6v golf cart batteries, after selling the old atomic for I think $400. I could have gone cheaper, with a salvaged forklift motor and controller, but I did not want a brushed motor. Salvaged golf cart equipment can be used as well, and is sometimes cheap.

What I like the most about my electric drive is the maneuvering characteristics. With a diesel, you have a minimum idle speed at 600 to 700 RPM. To go slow, you have to "bump it" in and out of gear. When backing, this creates a LOT of lateral force that you have to deal with. With electric, you can ghost along at 50RPM or less. You don't have to cross your fingers when hitting a start button. Flip a switch. It's on. Twist a knob. prop turns. Instantly. Boat hard to tack? No crew? Leave the drive in standby. When you are ready to tack, give it some throttle and power through onto the other tack.

There are electric outboards, too. Not as efficient as inboard, but portable. There is the Torqueedo line, and also some more serious outboards from 5kw up to 12kw, and there are a lot of homebuilt ones out there using the carcass of an old motor with the powerhead replaced by electric.

Best of both worlds of course is hybrid. A pulley on the prop shaft, and you can belt drive it with the electric motor. Or start the diesel and turn the prop with that. Optionally you can set the regen control so that the turning shaft drives the motor and the motor becomes an alternator, the output of which is conditioned to clean DC to charge the batteries. Lots of options.

If you need long range you are probably going to want to go diesel, or at least have a gas outboard for backup. Long range for electric, without recharging, is like 100 miles or so, typically, and that is doing a knot or less. Double the batteries, double the range. How many thousand pounds of batteries do you want to carry?

Cheapest way to go is 6v golf cart batteries. A typical small boat installation is 8 of them in series for 48v and about 220ah. Sams Club has them for about $85/ea, plus core fee and tax, and they are around 75 or 80lbs each. Best bang for the buck. Higher tech batteries like LiFeP04 or LiIon will need a good BMS (Battery Management System) for safety. Some e-boaters use AGM but I don't like them for numerous reasons.

For VERY short range, i.e. JUST docking, a 48v e-bike battery is a nice compact portable solution. A 20ah pack with BMS built in starts at around $420 via ebay from China. As a bonus you can use it to power your bike, with a $200 or less hub motor kit. That same battery, and a 36v PWM controlled trolling motor, and you have an extremely portable propulsion system for a boat under 30 feet. Switch it to your dinghy as needed.

Yes, you can recharge from solar. Realistically, you want a bare minimum of about 600w of solar, and this is in a place with good sunlight. Thats a lot of solar for a small boat. I will someday have 2kw of solar panels but that will be on a canopy covering my entire boat. Mast and sails greatly reduce the performance of solar panels, BTW. Don't even think about wind. On paper, it takes about a 10 foot diameter turbine to give you 1kw of juice. Not very practical. And real world performance usually lags theoretical performance or even advertised performance by a great amount.

Some guys keep a portable 2kw or so gasoline powered generator onboard for get-home emergencies. It is very inefficient, but as a backup system it is worth considering.

Again, IDEAL application of electric drive, if you are not just into it for the science and technology and tinkering aspect, is for in and out of the marina, especially for day sails, recharging from shore power. If you are one of those guys who actually like to SAIL his sailboat, and doesn't mind being becalmed, it is hands down superior to diesel. For long range motoring, you need to think about something other than a pure electric solution. LOTS of solar, or diesel drive, hybrid, or a genset.

[navy davy]

Electric motors are the way to go and are ready for prime time ..... Here is how ! ..use solar ,wind, and hydro charging to the batteries and have a diesel generator for when the other renewable energy venues are not keeping up with the batteries ! Be sure to use AC electric motors because they are brushless and last a long long long time ! Lead acid batteries are not the ones to use because they can be killed easy by discharge over 50% and only charge up to 90% , sooo to overcome the battery situation , lithium batteries can take as big a charge as you can throw at them and hold their charge well but I like the firefly Oasis carbon foam batteries because you can discharge them 95% thousands of times without hurting the battery and they charge quickly and almost 100% so when you are without wind and you want to keep moving , just kick on the diesel generator and power those AC motors untill you run out of fuel if you want ! There is a gunboat that has this setup , it works ! And the AC motors can outrun and out power diesel engines ! There is YouTube videos of tug o war between two cats and race between two cats ! Electric won both times ! Got money ? Go for it , but most sailors are too broke to pay for the initial setup ! 😶

[seandepagnier]

I started out with electric, I have never used engine.

I can say it works fine, and I was able to go 3 knots using half my deck area in solar panels without battery draw. I could motor 10 hours using 8 golf cart batteries.

Please don't expect to have a very efficient system if you use the existing propellor shaft. It is optimized for convenience not energy efficiency for diesel inboards. Really sad. If you want efficiency, consider the size of a fish or whale's tail to it's body.

In other words, you need a propellor diameter approaching the beam of the vessel. At least, every doubling in propellor diameter gives 40% more thrust for the same power input (lower rpm more torque) It's much better to move lots of water slow than a little bit fast.


Eventually I realized you don't need electric propulsion, in fact, sails are more than sufficient, and I have also an excellent sculling oar which I used yesterday to move against the tidal current despite having 2 year old paint, and about 1 inch of bottom growth.

[GrowleyMonster]

Originally Posted by navy davy

Electric motors are the way to go and are ready for prime time ..... Here is how ! ..use solar ,wind, and hydro charging to the batteries and have a diesel generator for when the other renewable energy venues are not keeping up with the batteries ! Be sure to use AC electric motors because they are brushless and last a long long long time ! Lead acid batteries are not the ones to use because they can be killed easy by discharge over 50% and only charge up to 90% , sooo to overcome the battery situation , lithium batteries can take as big a charge as you can throw at them and hold their charge well but I like the firefly Oasis carbon foam batteries because you can discharge them 95% thousands of times without hurting the battery and they charge quickly and almost 100% so when you are without wind and you want to keep moving , just kick on the diesel generator and power those AC motors untill you run out of fuel if you want ! There is a gunboat that has this setup , it works ! And the AC motors can outrun and out power diesel engines ! There is YouTube videos of tug o war between two cats and race between two cats ! Electric won both times ! Got money ? Go for it , but most sailors are too broke to pay for the initial setup ! 😶

For some FLA batteries, an occasional dip below 50% is not a death sentence. In fact, the rare discharge to 30% will only marginally reduce battery life for some. This is of course only for true deep cycle batteries. Talking dedicated energy storage system equipment, or golf cart batteries. I charge mine to 100% routinely, and leave them on float. I do a proper equalizing charge twice a year. Three years in, they are slightly better than when they were brand new. I expect to get 2 to 4 more years out of them.

There are brushed motors over 100 years old that still run just fine. No need to trash brushed motors. Changing brushes every 10 years or so is a trivial task. Also, what most of us call a brushless DC motor, or BLDC, is also often referred to as a PMAC, or Permanent Magnet AC motor. Both types are more efficient than inductance AC motors. In an inductance motor, the controller supplies power to both stator and rotor coils. DC brushed or brushless motors have permanent magnets for the rotor, and require current only for the stator coils.

Lithium batteries can pose a serious fire risk on a boat. More so than FLA, anyway. With a BMS failure, things can go north pretty quickly. Just sayin. Lithium has a lot of advantages, but cost, and safety, are not among them. Yes you can routinely discharge them to near zero. Yes they weigh less and with a proper BMS, will last longer. But that is not always the best solution. Depends on the useage and user. Don't throw the lead battery under the bus. It is perfect for some of us.

I am hearing good things about the carbon foam batteries too. But, do you have them on your electric boat? How long have you had them? Just curious. Got pics?

As for tug of war contests, that is a no brainer. A given hull can easily carry three times as much power in electric motors than diesel engines. Engineer an electric boat for HUGE power output for short duration? Simple. No braggin rights there. I could easily gang up a half dozen 12kw motors that together weigh less than a Beta 10HP diesel and take up less room as well, and have 72kw, or 100HP, sustained power, and over 200HP peak for a minute. But the cost is to the batteries. Or generator. Sometimes apples are better than oranges. Sometimes, not. OTOH, a turbocharged nitro diesel hotrodded and ran to insane RPM can surprise folks with its power, too. Basically, a tug of war doesn't really mean much.

Many ships are diesel/electric. I am a seaman, BTW. I have been on a diesel/electric cruise ship, a dredge, and a cable ship. Every other ship I have been on has been either steam turbine or diesel. Diesel electric is desired in some applications for maneuverability and flexibility, and for operating at low power levels for long periods of time, which diesels don't really like. Most ships use low speed direct drive two stroke or increasingly these days four stroke diesels, for efficiency. Warships are increasinly turning to gas turbine propulsion.

The use of electric drive for sailboats is a special case, which is why the technology is finding a lot of converts these days in spite of being a whole different way of doing things. Niche market, you might say.

[valhalla360]

Originally Posted by keith4001r

I've been a diesel truck driver since 1983 so I get how much energy a gallon of fuel contains. I also know I've spent many hours on the side of the road broken down, lots of those times were engine (or fuel) related.
The sun will shine eventually and it's free. As I said earlier, I will have a small generator to charge back up if the sun is bashful. I only want mechanical propulsion to get in and out of a slip and for an emergency.
Weather forecasts are everywhere, I won't go out on calm cloudy days and if I get caught out, I'll sit with a drink while the generator charges up the batteries.

So thanks for all the responses, positive or negative (see what I did there?).
Thanks for the links and the advice.
Thanks for being a sailing community that is willing to share information, advice and opinions.

I wouldn't count on an electric system never breaking down...simply different things break down. (can you rebuild the control unit?)

The sun may shine but a huge solar array may be 2000w. In ideal conditions, that will put out about 3hp. Of course anything other than clear mid-day sun and it's putting out a small fraction of the rated wattage. Likewise, if you plan to use a little 2000w honda portable as backup (a large built in diesel generator would blow any cost savings), you are down to around 2hp (continous output is limited to 1600w). Your average 30' monohull runs 15-20hp diesels, so you are way down on power.

Against a good headwind or current (and the Georgia coast has lots of currents), you won't be able to make any headway.

If you only need to get in and out of a slip and are willing to sit waiting for hours for the wind to die down or the tide to change, it can work but you will be seriously limited for weekend type cruising.

[Dockhead]

Originally Posted by keith4001r

Respectfully-
That's my problem, my Google-** has always been weak. I've never been able to get search results I was looking for even after people said there are thousands of threads on the subject. My search always comes back with either nothing or 1 million things that might mention for example the word diesel or mention the word electric or mention the word replace. This is why I ask specific questions looking for specific answers.
I was looking for someone who had actually done the conversion with the hope that I might take this to PMs and pick their brain.

So...

Anybody?

I think it's actually pretty easy to summarize the mass of discussion.

* Electric propulsion fairly expensive, but might work just fine for light usage -- principally getting in and out of marinas in reasonable weather and otherwise doing everything else under sail.

* No substitute for diesel if you expect to motor any kind of distances in calms or motor against the wind in strong weather.

* Hybrid electric propulsion -- trying to get the range and power of mechanical drive diesel propulsion by pairing an electric motor with a diesel generator -- doesn't really work at the scale we have and technology which presently exists. Because the generator has to be so big, and efficiency losses converting to electricity and back, and all the weight and volume of so many systems.



I think you will get it more or less right if you think of electric propulsion as an enhancement to the functionality of an engine-less boat, rather than as a substitute for diesel propulsion.

A diesel auxiliary engine -- they way they have been specified for the last few decades -- turns a cruising sailboat into a truly dual propulsion vessel, which can either sail or motor, or motorsail. If you use your boat like this, you will be disappointed in electric propulsion.

However, if you are experienced sailing engineless boats (I am, for example), and don't mind using your boat that way most of the time (I do mind, but YMMV), then you might be delighted with the advantages of electric propulsion -- silent, clean, simple, no fuel, etc., etc. This remark of yours: "I only want mechanical propulsion to get in and out of a slip and for an emergency." -- sounds like you might be a good candidate.

[TheThunderbird]

I suppose a heavy duty diesel coupled to a charger could offer a mix of the Two worlds' advantages.

But a few engines are set for additional torque connection.

Another limitation is Voltage, proportional to power, and installation costs. Above 70V risks are high

[valhalla360]

Originally Posted by TheThunderbird

I suppose a heavy duty diesel coupled to a charger could offer a mix of the Two worlds' advantages.

But a few engines are set for additional torque connection.

Another limitation is Voltage, proportional to power, and installation costs. Above 70V risks are high

Actually the worst of both worlds:
- Heavier
- More Complex
- More cost
- Less efficient

There really is nothing it does better. It isn't even good for running house electrical loads as a generator sized for propulsion is massive overkill for house loads.

Not sure what you are implying about torque. Assuming the generator is matched to the engine, torque isn't an issue.

The voltage isn't a big concern if you are OK with running a 110v or 220v system. Yes, it needs respect and proper installation but no more dangerous than your Mr. Coffee.

[Jim Cate]

This remark of yours: "I only want mechanical propulsion to get in and out of a slip and for an emergency." -- sounds like you might be a good candidate.

I'm struck by the "emergency" part of the statement myself. Many "emergencies" are situations where the minimum power present in the proposed electric system would be sadly lacking. Other "emergency" scenarios would over tax the range limitations.

I'd say that only the "in and out of a marina berth" application is well suited to the electric drive as described.

Jim

[Dave_S]

You have probably seen this but these guys did this for US$1400. It's worth a look if you haven't seen it.

Sailing Uma— Electro-Beke

[hafa]

One thing I've not seen nor heard of is a prop shaft that can be directly driven by either an electric motor or a diesel engine. Did I just miss it?

[StuM]

Originally Posted by Dockhead

This remark of yours: "I only want mechanical propulsion to get in and out of a slip and for an emergency." -- sounds like you might be a good candidate.

Depending on what sort of emergency you are anticipating.