Switched to Electric

Santanasailor

Charter Member. Scow Mafia
1,360
710
North Louisiana
We are using a 30lb thrust trolling motor on Anna Eleise.  Finally sold the, always needing an annual carb rebuild, small four cycle outboard from a normally very reliable manufacturer.  It had not run in several years and virtually gave it away.  Still, while the electric trolling motors are not infallible and usually require replacing about every two to three years, the replacement cost is less than than a carb rebuild.  

I suppose the best plan would be for a small inboard electric.  There is certainly plenty of room under the Santana’s cockpit.  However, the practical solution, cost wise,  and the direction we will go is to a 4 or 5 hp Tohatsu.  It will do double duty on our Jon boat that we like to fish out in the cove we live on.  Weight is the key issue and that will decide the actual motor chosen.  

Still, the old Evinrude, sits in our shop for years, put it on a boat, pump some fresh gas in it, give it a few pulls on the starter and she chugs away.  Being an 8 hp, with a 25 inch shaft, It is way too large for the Santana.  

People can whine about how dirty/nasty two cycle outboard are, but never have I heard many complaints about old fashioned reliability.    

 

Santanasailor

Charter Member. Scow Mafia
1,360
710
North Louisiana
So are sailboats.
Not exactly, I would not refer to Brenda and I as being particularly wealthy but we do enjoy our sailing.  

Its where you live and how you live and what your priorities are.  Big city thrills are big city pocketbook spills.  Live in the outback and enjoy the Whip-poor-wills.  (And some damn fine sailing) 

 

The Q

Super Anarchist
So I think he says it is an 85 hp engine, with two 10 kw electric motors. A bit later he says the electric power is equivalent to 2/3 of the diesel power. Jon Favreau school of physics? 20 kw is 26 hp if 100% efficiency is assumed. It is an interesting solution, but you should love it for what it is, not what it isn't.
I may have pointed out before but the listed power of an ICE engine is almost always the power made without the losses of water pumps, alternators and gearboxes . Not the tail shaft horse power.

Electric, although there are losses, they are a lot less at the shaft than a complete Ice engine.

 

Elegua

Generalissimo
I may have pointed out before but the listed power of an ICE engine is almost always the power made without the losses of water pumps, alternators and gearboxes . Not the tail shaft horse power.
My understanding is since the 70's SAE and JIS measure net HP at the flywheel with all accessories. So no drivetrain losses, both other parasitic loads are present.  Not sure that changes the answer...

 
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DDW

Super Anarchist
6,712
1,243
Many zealots in the electric boat business simply overstate the power output of their product. Call it lying, marketing puffery, whatever, it is simply not true. Net SAE, JIS, and DIN output includes everything on the engine (but not the transmission). At the same time, many electrics are being advertised on input power, not output, and they are only about 90% efficient. 

 Electric power is a great idea. Sell it and love it for what it is, not what it isn't. 

 

floater

Super Duper Anarchist
5,164
887
quivira regnum
People can whine about how dirty/nasty two cycle outboard are, but never have I heard many complaints about old fashioned reliability.
I had a two stroke outboard on my first boat. I still suffer from PTSD from its lack of reliability (although I did learn how to sail in and out of my slip because of it). but now, I am only just beginning to trust my diesel (which I have been assured is in fact much more reliable that that old POS gas/oil fired evinrude). lol.

 

DDW

Super Anarchist
6,712
1,243
If you think about a 10 kW motor running at 95% efficiency  (I hope any motor you use for propulsion would have that sort of efficiency). So 9.5 kw output, 0.5 kW waste heat. 500 watt is like a small space heater operating on 1/3 power. Pretty easy to air cool with some cooling fins on the casing and not heat up the interior of the boat too much.
Most of the BLDC motors I have looked at are 90%, maybe a bit less if everything (batteries, controller, etc) are looked at. Very few electric motors are 95%. Yeah, 10 kw that is only 1000W rejection, not too bad for air cooling, though it is being released in a small volume. But also only 12 hp output. Nice for a 25' boat in fine weather, not so much if more demanding circumstances. 

Aircraft have lots of airflow, but big heat sinks are also very draggy. There is currently a big shift in self launched and "sustainer" sailplanes, moving from ICE to electric. This is a pretty good application case as you need significant power for only ~10 minutes. For self launching around 30 KW is required (the ICE self launchers are 45+ KW). The motors are typically in the full airstream and air cooled, but on the edge of overheat always, and many will only allow full power for like 3 minutes then you must back off. Of course they are using the smallest possible motors for this as weight is a factor, on a boat not so much. 

 

167149

Super Anarchist
ok there's a lot of knowledgable DC power people here right now so i'm going to ask a sort of pertinent question, My old man bought an electric scooter thing (called a "Harley" of all things) from china, it has a 60volt battery pack and the charger says it's output is 67.2...2.0amps, this charger is dead/wont go  and having a look online i noticed that this output voltage amps etc is available not just 2 amps but 3,10,20 etc etc amp output as well, I assume it's charging a ithium ion battery pack, my big question is that say ordering a 3 or 10 amp charger as opposed to 2 amp is there any likelyhood of battery damage occurring  or is this more or less going for a rapid charge setup, apart from makita battery tools my familiarity with batteries other than lead acid is virtually zilch so any info on this is good for me

 

Bull City

A fine fellow
7,201
2,840
North Carolina
ok there's a lot of knowledgable DC power people here right now so i'm going to ask a sort of pertinent question, My old man bought an electric scooter thing (called a "Harley" of all things) from china, it has a 60volt battery pack and the charger says it's output is 67.2...2.0amps, this charger is dead/wont go  and having a look online i noticed that this output voltage amps etc is available not just 2 amps but 3,10,20 etc etc amp output as well, I assume it's charging a ithium ion battery pack, my big question is that say ordering a 3 or 10 amp charger as opposed to 2 amp is there any likelyhood of battery damage occurring  or is this more or less going for a rapid charge setup, apart from makita battery tools my familiarity with batteries other than lead acid is virtually zilch so any info on this is good for me
THREAD DRIFT ALERT!!! THREAD DRIFT ALERT!!! THREAD DRIFT ALERT!!! THREAD DRIFT ALERT!!!
 

Bull City

A fine fellow
7,201
2,840
North Carolina
Regarding batteries, I have often thought how wonderful it would be if battery weight could be incorporated into ballast.

My 4K Wh battery weighs about 100 lbs., which gives me let's say 25 nm range at 3.5 knots. My boat has 1600 lbs. of ballast. If ½ of that were a battery, say 800 lbs., that would give 200 miles.

 

Zonker

Super Anarchist
10,201
6,396
Canada
Probably best to see if you can find a seller of these scooters on ebay or Alibaba and get the proper charger.

Li-ion can absorb very high charging current, but it depends on the battery management system which may not be very sophisticated. I'd be super careful here.  Li-ion battery fires are a (bad) thing.

 

Zonker

Super Anarchist
10,201
6,396
Canada
My understanding is since the 70's SAE and JIS measure net HP at the flywheel with all accessories. So no drivetrain losses, both other parasitic loads are present. 
The output generally does not include the gearbox for marine engines because many different gearboxes can and are fitted. But gearbox losses are in the 5% range max.

My favorite is "equivalent in thrust to a XX HP motor". Which is bullshit because it all depends on prop size and gearing. And you don't motor around at zero knots, which Torqueedo is comparing thrust at.

 

chester

Super Anarchist
6,650
1,606
Regarding batteries, I have often thought how wonderful it would be if battery weight could be incorporated into ballast.

My 4K Wh battery weighs about 100 lbs., which gives me let's say 25 nm range at 3.5 knots. My boat has 1600 lbs. of ballast. If ½ of that were a battery, say 800 lbs., that would give 200 miles.
what a great question/thought...Why couldn't batteries be housed in keels.

 

jmh2002

Member
314
245
Dashew's boats incorporate large battery banks as part of the ballast and have purpose built compartments in the keel stub. 

Obviously they are not just tossed down in the bilge sump... 

 

Zonker

Super Anarchist
10,201
6,396
Canada
On small boat, the keel isn't wide enough for COTS size batteries.

Just for info I figured out the density of a typical golf cart battery. About 2.2.  Lead is ~11.3.  Steel is 7.8.

So not exactly ideal for keeping the wetted surface of a keel reasonable or as a ballast material (if you think about it there is significant volume taken up by electrolyte, plastic casing, terminals on top, wiring (which I ignored). 

Li-ion golf cart batteries are lots worse density - about 1.1 or about the same as water! By the time you fit hold downs and wiring you'd be better off filling the top of the keel with a water tank. Which is simpler than a battery bank.

 


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