Converting a boat to electricity

[Simpo Two]

anonymous said:

[redacted]

Back to basics is always worth considering. Certainly anything that needs 3-phase is out as marinas only have normal mains.

Leisure batteries are comparatively cheap and plentiful... let's see if I can do some O-level physics...

A Hankook XL31 leisure battery provide 130Ah at 12V and costs £104. https://www.batterymegastore.co.uk/batteries-by-ap...

My boat has a 40bhp engine but i never use more than half of it. 20bhp is 15kW. So to run for 12 hours at 15kW needs 180kWh of battery.

130Ah at 12v > Ohm's law > 1560W or 1.56kW. So 180/1.56 = 115 batteries...

OK basics didn't work!

The molten sodium floating Chernobyl seems to win on paper.

[anonymous-user]

Simpo Two said:

Max_Torque said:

Second hand 3 phase 30kW AC motors are cheap and easily available

What's the reason for having an AC motor and then having to buy an inverter to make it work? Is it just that AC motor + inverter = much less wonga than a DC motor?

Max_Torque said:

If you bought a couple of used EV battery's from a crashed leaf or similar (budget around £2.5k each) , then a simple rewire of the 7.5v modules will give you the voltage you require and 50 KWh of energy, enough for 2 hours flat out, or 4 hours at quarter power (~half speed)

2-4 hours is way short of requirement (12+ hours). But what speed is 'flat out'? If flat out to you is 20kts then as I only need 5kts the range/running time might work...

AC motor because they are tough, reliable and easily found second hand. No brushes to wear out, no issues with magnets and can be run quite hot, easy to drive too, and have a wide constant torque speed range (good for getting a draggy boat moving)


a 30kW motor is 40 bhp. So it'll go as fast as it did with 40bhp (actually, probably faster, as you'll be able to fit a much better prop in terms of efficiency)

Boats have a horrible power vs speed curve, goggle "displacement hull power vs speed" to get an idea, and also for several online calculators that can estimate the characteristic for your boat.

One option could be to also buy a decent sized (say 12kW) diesel gen-set to use in emergency.

[hidetheelephants]

The power required for the OP's proposed use is modest;

7mph = 6.5kW
6mph = 4.25kW
5mph = 3kW
4mph = 2.1kW

On that basis a 8-10kW motor is ample for the purpose.

From psychosnail's speed calc thingy;power/speed curve for a typical 27' monohull.

Edited by hidetheelephants on Sunday 23 September 23:29

[Simpo Two]

I like this man!

Thanks also to MaxTorque; I'd considered a portable generator for emergency top-ups but it would need to be very portable to fit in a locker - if it's officially part of the boat the dear EA will rook me for even more licence fee and give the BSS man more things to fail it on (assuming I hadn't managed to distract him when he was about to lift the lid on the plutonium core... 'What's this?' 'Oh nothing - look, an eagle!'). And besides, every cranny of the boat would be full of batteries. Even the cutlery drawer will have some old cordless drill batteries cobbled together in it

All I need to do now is get some plasticine trousers and aim for the moon...

On a more serious note, and simple cash aside, this seems to me a massive risk - because the worst case scenario is that the new gubbins doesn't do the job for some unanticipated reason... so I end up with a boat that doesn't work and the old engine has been sold on eBay...

[peterperkins]

Now you are talking, call it 5kw for 6mph (including electrical losses in the controller/motor/batteries etc)

So for 12hrs you need 60kwh and a leaf pack or two is looking a little more realistic..

You could start off with one pack and if it works as indicated then add another/more to achieve your ultimate range goal.

Are the riverside hookup points really able to deliver a full 16A / 3kw or so for charging?
What do they charge £? per kwh?
Charging your 60kwh pack from flat would take a minimum of 20hrs...

As MT says a 10kw ish old ac brushless air cooled motor will be relatively cheap..

I ran a 96 volts 12kw ac induction motor in my old solarvan. It used a 450A Zapi ac drive.

Something like this though is cheap as chips.. EV Conversion kits..

https://www.alibaba.com/product-detail/Electric-Mo...

Edited by peterperkins on Monday 24th September 07:49

[dhutch]

Simpo Two said:

Stopping for snacks, tea and lunch are built into the boating experience .

Your doing it wrong! Get a set of your own stamped pint glasses and you can get a round in at each pub without stopping!

Simpo Two said:

...3-phase is out as marinas only have normal mains...

Basically right. Most will actually have three phase, but it will be in the workshop and or one outlet for a welder, so gaining access would be a pita and or a phonecall to each boat yard along the way!

As for is 16a (single phase) is available, it depends. The standard connection is a 16a blue ceeform but often they are on a smaller breaker, modern visitor moorings with 16a on tap are becoming the norm I think from what I see canalside, metered, but for instance or marina you pay a fixed rate unmetered but only get a 2-6amp feed depend on the standing rate you pay.

Canal comment in detail on what's common on rivers.


Daniel

[Simpo Two]

At my marina there's a monthly standing charge - £8 I think - then units are prepaid by card and despatched via ceeform. Apparently a law stops them reselling units at a profit.

There are no workshops or welders so I'm guessing 13A is the limit. No big deal as there are usually a few days between trips. Recharging is the least of my worries!

[anonymous-user]

An 8kW diesel genset would massively increase your range:

8kW_genset

You could use a single 24kWH leaf battery for the peak power / high speed dashes, and the genset for cruising an emergency re-charging (ie where no mains connection is available)

[Simpo Two]

Max_Torque said:

An 8kW diesel genset would massively increase your range:

8kW_genset

You could use a single 24kWH leaf battery for the peak power / high speed dashes, and the genset for cruising an emergency re-charging (ie where no mains connection is available)

I could use the existing diesel as the generator...!.... but a major part of the exercise is to avoid the need for water cooling. Hybrid doesn't meet the brief unfortunately. I'm not convinced of the point of running a diesel to charge batteries to run on electricity... you may as well sell the batteries and connect the diesel to the propeller

[Huntsman]

Simpo Two said:

I could use the existing diesel as the generator...!.... but a major part of the exercise is to avoid the need for water cooling. Hybrid doesn't meet the brief unfortunately. I'm not convinced of the point of running a diesel to charge batteries to run on electricity... you may as well sell the batteries and connect the diesel to the propeller

I looked at going electric for a 16ft harbour launch, I just could not make the sums add up.

The tech is there, but not at the price point, plus, at the moment, its a bit like using megasquirt to fuel inject your car, it needs masses of development and fiddling, no off the shelf solutions ready to fit, it needs a whole new level of plug and play.

Have you seen those Greenline hybrid slowbo's? I bumped into a chap on one in Bembridge (metaphorically that is, I didn't crash the Huntsman into him!) He was very proud that he'd got from Shamrock Quay to Bembers all electric, no need to run that pesky noisey diesel. There seemed to me 2 flaws in his wonderful tree hugging slobo'ing. First, he'd charged the batts from shorepower which is at least 50% fossil fuel electric, but worst, in order to get the range, he'd done the trip at 4 knots! 4 fking knots down the fking Solent! I do more than 4 fking knots at idle with just one engine in gear! 4 fking knots my arse, whats the fking point of that when you could go fking blam blam blam blam 30 knots at 20 gallons an hour burn? Hmm? Hybrid Greenline my arse, pointless!

[hidetheelephants]

Simpo Two said:

Max_Torque said:

An 8kW diesel genset would massively increase your range:

8kW_genset

You could use a single 24kWH leaf battery for the peak power / high speed dashes, and the genset for cruising an emergency re-charging (ie where no mains connection is available)

I could use the existing diesel as the generator...!.... but a major part of the exercise is to avoid the need for water cooling. Hybrid doesn't meet the brief unfortunately. I'm not convinced of the point of running a diesel to charge batteries to run on electricity... you may as well sell the batteries and connect the diesel to the propeller

There's no reason you couldn't have a keel cooler for something that small, although I appreciate the desire to get rid of the noise, smell and vibration of diesel; a possible compromise might be a Whispergen, they use a stirling cycle to produce about 1kW while making hot water. How often are you really going to be doing 12 hrs underway non-stop? There's also the issue of charging, if the only supply you can count on getting at marinas is a 13A socket then that is a real limit on power usage/supply; assuming you arrive at a stop at 4pm with the intention of leaving for the next stop at 9am, that's only going to give you 47kWh, a half-charge for the hypothetical 90kWh battery.

[Simpo Two]

hidetheelephants said:

There's no reason you couldn't have a keel cooler for something that small

I can't find anyone to do it.

hidetheelephants said:

How often are you really going to be doing 12 hrs underway non-stop?

It's not a question of 12 hours non-stop, it's a question of cruising up a river for a day, mooring in a field overnight (no power) then returning.

hidetheelephants said:

There's also the issue of charging, if the only supply you can count on getting at marinas is a 13A socket then that is a real limit on power usage/supply; assuming you arrive at a stop at 4pm with the intention of leaving for the next stop at 9am, that's only going to give you 47kWh, a half-charge for the hypothetical 90kWh battery.

The only marina in the picture is my own; I can't think of anything worse than overnighting in an alien marina (it doesn't work like that inland). I like fields. Once I get back to base the boat can sit and happily recharge for several days.

[hidetheelephants]

Simpo Two said:

hidetheelephants said:

There's no reason you couldn't have a keel cooler for something that small

I can't find anyone to do it.

You're being poorly served by luddites; keelcoolers are available off the shelf to bolt onto the underside of your boat. The toughest decision is whether to retain the wet exhaust(requires keeping a water intake and pump which may block with weed) or fit a dry exhaust; there are pros and cons for each.

[Simpo Two]

hidetheelephants said:

The toughest decision is whether to retain the wet exhaust(requires keeping a water intake and pump which may block with weed) or fit a dry exhaust; there are pros and cons for each.

Indeed, it's my back-up plan if electricity proves unfeasible - which it probably will, but I like to investigate all angles. The simplest answer is to move the water intake from underneath the boat to somewhere it can be reached in an emergency, eg near the transom/bathing platform. But I'm not sure if the turbulence there would affect operation.

[Steve_D]

For your water inlet how about having two with a changeover valve. Then a pump joining the two.

When one blocks turn the valve to use the other. Then use the pump to blow the weeds out of the blocked inlet.

Steve

[anonymous-user]

Hows about a low powered "skulling" motor, that allow silent low speed cruising, nice when you want to slowly cruise in silence, say downstream?

That could be a realistic first step?

[dhutch]

If the issue is the inlet for the coolant blocking is the core issue here, I cant help but feel as said the way to solve it with investment here.

You could convert to a dry exhaust (assuming its currently wet) and then use a keel cooler, the layout of the boat/engine etc will determine how easy it could be to go to a dry exhaust.

But as said you could also change the raw water inlet/strainer setup to make it more robust. I don't know what you have currently or where it is blocking, but you can get a range of hull fittings some which are better than others and or leg inlets, and you can also get duplex strainers so as said you can swap over when one is blocked and unblock the first either while going or at your leisure in the evening.

Depending on how great and issue it is and where the blockage tends to form, you can have more than one intake, and more than one strainer, and even a back-washing system as said.


Daniel