Electric outboards

[pcatterall]

Suprised that the recent PBO trials on 3 of these stir up this debate again.
The bigger of these looked quite impressive though expensive
I think I would do without the special battery and spend my money on two good external batteries.
I can see a good use for these if you have good charging facillities or are just doing short trips ashore and back.
Any one actually using one of these??
Regards

 

[Colvic Watson]

Yes. Outstanding technology, but I declare an interest as I've just become a dealer for them. Battery technology is the hold up and the reason that lots more people don't have them, but it's also holding up the development of lots of other technology; and it's the reason that I need to carry 80kg of lead and acid, just to run a few cabin lights and show me where the plotter thinks I am. The Travel 401 and 801 adequately replace a tender's petrol outboard because of the efficiency of the 'clip on' battery and the 46% efficiency of the motor, it will happily get you to and from a moored boat but do so without the hassle of petrol, oil, weight, smell and noise. The Cruise 2.0 (not shown in the PBO report) needs 24v from lead acid batteries but it punches a mighty kick for an electric o'b. Torqeedo are selling a lot of their units in Europe and the US.

 

[Channel Ribs]

Not the ones featured but I use a small electric outboard as an auxillary auxillary on Cottontail, which works a treat. It can easily be moved to the tender if it is too far to row (I use a smallish gel battery which is easy to lower into the tender for that).

As a manouvering thruster to the boat it is great, instant power at the twist of the grip and enough oomph to get into and through locks etc. Much nicer than starting the engine for the sake of 20 minutes - mostly in neutral. The inboard gets used to motor out of the channel and there is a voltage sensative relay which tops up the EO's battery while under power.

(I don't sell them by the way, so this is a consumer's perspective)

 

[William_H]

With all due respects to pasta_simon but I can't see it. 46% efficiency. I always imagined electric motors even more efficient than that.
But you can't get away from the fact that 1 hp equals 650watts and 650 watts is about 50 amps at 12 vollts. That means a lot of battery to give any power/ endurance. So as Simon says it is battery technology that is the hold up.
Small electric o/b obviously have their place in some circumstances but they rely on a very small amount of thrust being enough. Ok for a tender out to the boat? maybe until you get a headwind and sea.
So make sure you can augment the electric o/b with workable oars.
Don't expect too much from electric o/b and small battery. olewill

 

[pcatterall]

I have looked again at the trial. The Torqueedo uses AC which at 2 knots on the 3m Zodiac was 4 times as efficient as the dc motors and gave a range of 2 miles per 100watt hours.
This motor would drive the zodiac at 3 knots for 3 hours on its 10 Ah LiMan battery or 15 hours on a lead acid 110 ah at 50%.
These figures were a suprise to me, I guess I have only seen figures for dc motors before.
Does PBO get down under??
My 1960s Seagull is still going strong and now starts first pull!!

 

[MikeBz]

[ QUOTE ]
This motor would drive the zodiac at 3 knots for 3 hours on its 10 Ah LiMan battery

[/ QUOTE ]

What voltage is that battery? Can't be 12V surely... otherwise that's 0.06hp to do 3 knots...

Mike

 

[mandlmaunder]

Had an electric 'Thruster' motor until very recently, drove our 'Tinker' - was great around the marina/in bays and close to shore in the UK, quiet enough so that we could talk to people on boats as we passed. Hoicking the battery in and out was not too much of a pain and it never let us down.
However, the comment made earlier regarding effects of wind and sea conditions is what finally made the decision to get rid of it....it had been unused since we left the UK 5 years ago!

Btw....an electic motor on AC? Long extension lead???????

 

[pcatterall]

Sorry!! 3 knots for two hours with the 10 Ah internal battery(I read the wrong line on the chart) and 7 hours at that speed with an external 110Ah battery at 50% discharge. The 7 hours from 55Ah doesnt tie to the 2 hours from 10Ah but possibly the 50% discharge was not accuratly measured ( the flat 10Ah battery should be a more accurate measure?!!.

And, yes, AC motor not AC power!!
This is what the testers observed.

 

[Colvic Watson]

[ QUOTE ]
What voltage is that battery? Can't be 12V surely... otherwise that's 0.06hp to do 3 knots..

[/ QUOTE ] It's a 24v battery (all their ob's are 24v). The current draw for the Cruise 2.0 (equivanlent to 6HP petrol ob) is 10amps at half throttle and 50amps at 75% throttle - someone with a lot more understanding of elctrickery could please explain that for me!

The figures on efficiency rely on the much greater efficiency of electric motors. But in terms of weight, gasoline produces approximately 600 times more energy than lead acid batteries. That's how a petrol ob gets away with being less than 10% efficient, yet runs for hours at full throttle on 10kg of petrol.

 

[pvb]

[ QUOTE ]
It's a 24v battery (all their ob's are 24v).

[/ QUOTE ]As you've said you're a Torqeedo dealer, you obviously know about the product, but their website claims that the 401 models are 12v - can you get that corrected?

 

[pcatterall]

The cost of fuel comparison was quite interesting as well.

 

[Colvic Watson]

I was a bit surprised by that - 1p per mile with the Rolls batteries against 30p per mile for the petrol ob - but that didn't include the replacement cost of some expensive batteries, so it wasn't a completely fair comparison; still it looked interesting.

 

[MikeBz]

OK, so 2 hours on a 24v 10Ah battery is 120W. If the motor is 46% efficient then that's 55W of output, which is 0.085hp. Still quite surprising how little power you need to do 3 knots.

Mike

 

[jenku]

You can make 3 knots by rowing. How many horsepower is that?

 

[Colvic Watson]

If your correlation between watts and hp is correct, then it's more than surprising, it's a bloomin miracle! I'm not doubting your maths at all, just that there must be some other factor. You can't make a 2.7m Zodiac go at nearly 4 knots with just 8.5% of a horsepower. Or can you.......(cue the X Files theme tune)

 

[MikeBz]

To be fair I'd used olewill's assertion that 1hp==650 watts in my calcs. A quick google reveals that it's more like 746 watts, so revise that 0.085hp to 0.074! No I don't know what's going on either... Ignoring the hp conversions I'm still surprised that you can keep a dinghy going at 3knots for just 55W, I mean, that's only just over half a 100W bulb innit...

Mike

 

[Colvic Watson]

I guess it's what that power is doing - a light bulb is producing heat with the light as a bit of a by product, but put 100 watts through and amp, place the speakers near you ears and you'll be deaf in no time. If the 100 watts is turning a very efficient motor...?

Just out of interest, when we anchor in cool weather (ha ha, what's that?) we run a pair of electric blankets off an inverter on the domestic batteries; a whole night of toastie warmth uses just 27amps.

Going back to your calculation, either electrickery is super efficient at powering a motor, or we've missed something.

 

[pcatterall]

I should not have started this topic!!
Have had to do my own maths and I made it 0.66Hp !!
Still not much but if a 4Hp petrol jobby only produces 0.4 (10% as stated previously) and the Torqueedo gives out almost 50% ie 0.33 Hp they look similar.
Or did I do my figures wrong!!

 

[paulburton44]

I use a rhino on my Parker 235 at Rutland water.........it does very well for me...I have a 24ah gel battery ...

 

[Robin2]

Following the PBO article I had been looking at the Torqeedo website before this post came up.

Calculating power for a thrust producing motor (eg aircraft propellor, jet or boat equivalent) is notoriously difficult because, unlike a car, it does not have a rigid connection to the ground. I downloaded a Torqeedo booklet in which they describe output power as Thrust x Speed - presumably (but not definitely) the boat's speed. This immediately raises the interesting speculation that you get more power, for the same thrust, in a lighter (ie. faster) boat even though it may be consuming the same amount of electricity. This method of calculating power is why the Torqueedo seems inefficient.

I have never seen a petrol outboard's power calculated in the same way. The power that is normally mentioned for a petrol (or diesel) engine is roughly analogous to the input power of a Torqueedo. However it is common enough for the petrol engine power to be measured on a bench while it is not burdened by accessories or a transmission.

As far as I can see the Torqeedo uses a brushless motor (anyone interested in electric model airplanes will be familiar with them) and a 14:1 reduction gear. These brushless motors are capable of very high power outputs and high torque (for their size) as well as being very efficient - well over 80% usually. Because they have no brushes they need to have the DC power manipulated by some clever electronics to make them work. This means that the speed control is also very efficient.

Now, after all that, has anyone any experience using one of them - especially the powerful 2kw cruise version