Converting a boat to electricity

[Simpo Two]

(you know what I mean!)

27' GRP cabin cruiser, currently powered by 40hp inboard diesel. It's noisy and vulnerable to weed clogging.

Top speed required is 7mph (normal cruising speed 4-6mph), and enough power for a weekend trip - say 12 hours' cruising between charges.

Possible? And if so how much and where to get the bits?

(If the motor needs to be water-cooled that would spoil the plans a bit though)

[Simpo Two]

Thanks folks - I should point out that the boat is inland, and the marina has shore power, so recharging isn't an issue.

The Elysian 27 is very close so that would be worth pursuing. Also the Vetus link; my boat has quite a few Vetus bits.

Apparently 40hp is 30Kw... so if my sums are right that Vetus 2.2kW motor is only 3hp - that can't be right surely? Another website says 'The Oceanvolt AXC series is a modular system available in four power configurations 10kW, 20kW, 30kW or 40kW; the latter of these provides power to the equivalent of up to 100hp'. In which case I'd need 16kW...

PS That NauticExpo link looks very interesting; it's clear I need someone with experience to help me pick my way through the jungle. Unfortunately I don't think there are any!

Edited by Simpo Two on Monday 17th September 09:49

[Simpo Two]

bluesatin said:

Perhaps this http://www.hushcraft.com/

I found that but they seem to be hybrid systems, ie they retain the original engine.

[Simpo Two]

IforB said:

Simpo Two said:

bluesatin said:

Perhaps this http://www.hushcraft.com/

I found that but they seem to be hybrid systems, ie they retain the original engine.

Hushcraft do both. I would know, I took the picture of Bluesatin's boat...

Maybe they do, but how do I deduce that from their website? http://www.hushcraft.com/thrustpilot/

So they miss a possible sale!


Many of these websites seem to be a page of guff, a CGI image of a boat - and no actual real life examples at all!

Edited by Simpo Two on Monday 17th September 22:52

[Simpo Two]

I clicked on Products.

Happy to talk if they can provide a complete kit to electrify a 27' cabin cruiser.

As for Projects, the first two are hybrid, the third is about mapping the ocean floor.

[Simpo Two]

Will do - just realised I know his father! Thanks Ifor.

[Simpo Two]

Mr2Mike said:

How fast is the boat with the 40hp diesel engine?

I've never used all 40hp. At 2200rpm (less than halfway round the dial) it does about 6mph which is all I need and makes quite enough noise and wash.

I'm not sure if it would be best to have a motor that's flat out at 6mph flat out, or one with extra power that's not used. Are these things most efficient at max rpm? Talking of rpm, a gearbox could be an issue as I have no plans to change the prop.

One gotcha may be cooling. Some of these motors seem to need water cooling - and if so, a big advantage of changing over is lost.

[Simpo Two]

anonymous said:

[redacted]

There's shore power.

Thanks to Ifor I'm making constructive progress. Currently trying to evaluate costs, as there are costs and savings both on one-off and ongoing bases. There's an amount I'm prepared to invest but not more. Also a few technical/practical issues to sort out such as heating and hot water.

I had hoped that electric boats would be tariff free, but no luck, only a 25% discount


I know there are some brokers here - would an electric inland cabin cruiser be worth more than an identical diesel-engined version?

[Simpo Two]

NeilB12 said:

Heating and hot water could be provided by a Webasto / Eberspacher / Mikuni unit. Just need a small diesel tank somewhere.

Actually it has an Eberspacher D4 already, for hot air heating (but it's noisy and the control panel is too clever). Don't suppose it can do hot water too with some kind of conversion?

[Simpo Two]

Thanks Daniel; I'd need more than 8 hours but on the plus side I only need to do 6mph which should help.

Unless you're going to burn more electricity to run a cooling fan, air cooling doesn't really work on river cruisers so if it's not water-cooled it will just have to radiate. Hull cooling would be wonderful but no-one seems to have the courage to fit it to a cruiser.

[Simpo Two]

Thanks HTE, you're obviously well up on this subject. The first quote has come in and you're right, e32K fro Oceanvolt (24% VAT doesn't help). That makes the whole project a non-starter by a country mile, and assuming other companies are similar, I'd have to look at 'salvaged' parts... but is a random collection of second-hand batteries wired up with no warranty a wise way to spend even £10K? I can't think so.

I think the electric dream - not just for me but for the world in general, is a long way off yet. It can't cut the mustard and it's too expensive.

[Simpo Two]

hidetheelephants said:

Rob the battery out of one of these; the only down side is dealing with remelting the battery after it's been allowed to solidify, assuming you are cruising continuously for several days followed by a long period of no use then that would be manageable, the bms manages battery temp while charging.

Wow. Not sure if I'm up to remelting sodium nickel chloride though!

[Simpo Two]

hidetheelephants said:

It sounds very alarming, as does the operating temp range of 250-250C, but the charger controls all that and the alarmingly hot molten stuff is safely locked up in the battery and insulated from you by what is effectively a vacuum flask, so the outside is just warm to the touch.

YHM sir.

I wonder what the EA and BSS would make of it? They love electricity of course but are terrified of petrol so what would they make of a boat full of molten sodium?! Hopefully they'd be satisfied with just 'Batteries'!

[Simpo Two]

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...

[Simpo Two]

Chainsaw Rebuild said:

I'm no expert so forgive me if this isn't a workable idea; could you put solar panels on the boats roof to charge the batteries a bit while you are going along? perhaps you could alter your habits a bit and stop for once or twice for snacks/tea/lunch as well to give the solar panels time to top you up a bit more.

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

Unfortunately solar panels wouldn't come close to providing/replacing the power needed.

[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.

[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...

[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!

[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

[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.