Pete7
Well-Known Member
Yes and that includes us. So whilst we might be able to make it work, just not for a while yet, but worth keeping a watch on developments. Oh and the Ocean Volt solution was 40k euros the last time I looked.
E-propulsion I-Series (inboard)
- Thread starter DangerousPirate
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AntarcticPilot
Well-Known Member
Doesn't matter. I was merely using 12v to work out an equivalent measure of battery capacity in a form familiar to most of us. The point is that an hour of operation at full chat would need a battery capacity equivalent to 1250 Ah at 12V. In other words about 10 times my capacity of about 220 Ah lead-acid, which only yields a useable 110 Ah.
The only realistic way I can see to get a useful range would be to get the battery bank out of an EV, along with the battery management system (without the BMS it would probably be dangerous). My EV has a 65kw battery; that would power a 15 kW motor for 4 hours (it's good for up to 240 miles in the EV; I do about 4 miles per kW). But that would require serious amounts of space, and would be heavy enough to require serious consideration of the weight distribution. Again, my EV is significantly heavier than an equivalent ICE car.
dunedin
Well-Known Member
Unfortunately this thread is in the PBO forum - if we were Yachting World segment and thinking of buying a new yacht, this shows what is available for new build with a big budget - a fast sailing boat with an OceanVolt drive configured as a serial hybrid for huge range Xc 47 #1 – Hybrid |
Kelpie
Well-Known Member
There's no point thinking of electric propulsion in terms of a normal electrical system. It's replacing the entire engine and fuel tank, so you need to think in terms of how much space and weight that frees up.
A 280Ah LFP pack weighs around 25kg, so you could get 66kwh for the weight of a 250kg diesel engine plus 250l of fuel. Minutes the weight of the motor itself but they're not that heavy.
ithet
Well-Known Member
My back-of-envelope calculation just looking at fuel used and endurance to calculate energy requirement:
I have a 34ft AWB, that uses about 2l/h (typical cruise at 5.5kn), and a 70l tank, therefore 35hr endurance.
So, 2l/hr suggests around 8.5hp load on engine.
8.5 * 750 = 6,375watts (almost spot on to the graph at #18)
For same endurance:
6,375 * 35 = 223,125 w/h required. So, more than two Tesla's worth. How much are those batteries?
Electric propulsion for most cruising yachts would give a massive reduction in engine only range. Of course, one might be happy with a lower motoring range, it depends on ones usage. But I like enough range to know I can motor cross-channel and back if need be (there never seems enough wind). Already I carry extra fuel in cans. I know this is not the whole story as electric propulsion requires less energy input (due to lower shaft and gearbox losses?).
I have a 34ft AWB, that uses about 2l/h (typical cruise at 5.5kn), and a 70l tank, therefore 35hr endurance.
So, 2l/hr suggests around 8.5hp load on engine.
8.5 * 750 = 6,375watts (almost spot on to the graph at #18)
For same endurance:
6,375 * 35 = 223,125 w/h required. So, more than two Tesla's worth. How much are those batteries?
Electric propulsion for most cruising yachts would give a massive reduction in engine only range. Of course, one might be happy with a lower motoring range, it depends on ones usage. But I like enough range to know I can motor cross-channel and back if need be (there never seems enough wind). Already I carry extra fuel in cans. I know this is not the whole story as electric propulsion requires less energy input (due to lower shaft and gearbox losses?).
boomerangben
Well-Known Member
I wonder if this is going to be the limitation of electric propulsion of yachts - being big enough to sail fast enough to recharge the main propulsion battery storage. XC 47 looks interesting but a range of 30 miles on battery and 11kW generator for long range - at much reduced speed is going to disappoint someone used to filling a tank and having a range measured in more than three figures at 6 - 7 knots.
Then again it would be fine for getting in and out of a marina where a hook up is ready and waiting. I think buyers of EY (electric yachts) and hybrids are going to have to be very honest about how they expect to use their yacht when specifying it.
Pete7
Well-Known Member
I am not sure you will need to supply 15kW to the electric motor. We have the same yacht and I think that if you were happy to motor at a sedate 4 knots say cross channel because there is no wind, then you will need 2kW for 4 knots. 60 miles at 4 knots, say 15 hours which is 30kWh.
You won't get 30kW of LifePO4 in our engine space, so some will need to go in place of the diesel tank. The tank is on the port side and the boats already lean to port
So perhaps the wardrobe in the rear cabin has go and the space used for batteries. We have a taken ours out and put the freezer in there. So what size of motor? well Lynch do a 8kW electric motor about 11hp, though its not a direct comparison and does sound incredibly small, but it only needs to run at 6kWh to do 5 knots in calm water.
Why haven't we done it? because we only burn 100 - 150L of dino juice a year, not worth the effort. Oh and regen from sailing with the prop turning, doesn't do much if you can't regularly achieve 6 knots and preferably 7 or 8 knots.
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dunedin
Well-Known Member
I haven’t looked up the diesel tank capacity on this particular boat, but as a DC generator works at peak efficiency I wouldn’t be surprised if this long waterline length boat could run at 6 knots in hybrid mode for well over a thousand miles.
Certainly another similar hybrid I did the maths on could run for twice as far as its traditional diesel engine sister ship.
Trident
Well-Known Member
NO they will not - I'm not sure where you get your figures from but as a marine electrician I would never consider 485A through a 70mm cable - or even a 120mm cable (ok maybe that one if the distance from battery to motor was about 30 cm but I'd still worry)
In the real world the type of cable, the length of cable, the way its fixed or put in conduit all count. For example a 250 amp flow through 1.5 m of 70mm Oceanvolt multi strand (the best there is) gets it too hot to touch - upped to 90mm and still quite warm after 30 minutes of an air fryer on. Now with 120mm and fine. 400 amps would have been a fire. And thats 1.5m which is impossible for most battery banks and motors in a boat. More likely 4-5 m each way.
There is a very real place for electric motors but people must know everything required to do it safely - the fuse boxes, cut off switches etc must all be sized to the continuous current not the peak and thats very prices and bulky too. Nothing compared to the cost of the motors but its not a place to skimp.
lustyd
Well-Known Member
Oceanflex
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lustyd
Well-Known Member
You’re assuming this change will be made in isolation. It won’t.
I just fitted Starlink to my boat which means I can work anywhere, removing the requirement to motor back across the channel. We proved during lockdown that many jobs can and should be done remotely, paving the way for more freedom.
Continuing to use diesel long term simply isn’t an option so we need to work out alternatives. For those unable to work remotely I’m afraid that means local sailing only, so shorter range is fine. For those able to work remotely time isn’t an issue and neither therefore is range.
ithet
Well-Known Member
I was making an "all things being" equal comparison and concluded that current capacity limitations would mean a considerable change in the way I use my boat. You are ahead of the game in those changes so I think we are in agreement.
It was just a mathematical exercise without any regard to the environmental consequences or politics.
penfold
Well-Known Member
Only if the system remains at 48v; upping the voltage brings cable size back into practical limits.
AntarcticPilot
Well-Known Member
And increases the hazard. EVs have to be worked on by people trained to handle high voltages. On a boat, maintaining insulation might be a concern.
I think that serious adoption of electric propulsion will require a bottom up redesign, and that retro-fitting it will always be a second best.
dunedin
Well-Known Member
But according to some experts I spoke to, regulations in many markets mean different maintenance / certification challenges when go above 50V installations.
But yes electric cars are way above 48V - but are less likely to have their battery packs submerged under salt water in the event of a minor collision
Kelpie
Well-Known Member
They're also more likely to use NMC, whereas LFP makes the most sense for boats.
Alan S
Well-Known Member
OK then, required power is 15kW if you want to use full throttle. I took that as read.
DangerousPirate
Well-Known Member
Yeah, the longer this thread goes on, the less I think they are feasible for cruiser. Maybe for the weekend sailors who stay in their bay and lough and only go out during nice weather without any time pressure.
Until it's useable for the rest of us, we are limited by the current battery technology. Maybe in 30 years batteries will be small and efficient enough that we can store the required amount of energy. This is probably what my mate meant after he motored down the whole east coast of england because he had to be back in time for work after a 3 months sailing holiday with his family - he was livid because he had to motor the whole way as the winds were not in his favour and spent 600 pounds or something just on fuel. For the next 3 weeks he was constantly talking about getting an electric engine and putting more solar panels up, but then settled with a sad "It's not feasable. I can't carry that many batteries with me.".
But you can go completely off grid once the batteries are small enough for this. You got all the electricity you need, starlink for internet, watermaker for, well, water, you can fish every day, and use the electric engine. What do you really need at that point? Maybe food every now and then, but everything else is already possible to have without having to step ashore. Cool times to live in!
Until it's useable for the rest of us, we are limited by the current battery technology. Maybe in 30 years batteries will be small and efficient enough that we can store the required amount of energy. This is probably what my mate meant after he motored down the whole east coast of england because he had to be back in time for work after a 3 months sailing holiday with his family - he was livid because he had to motor the whole way as the winds were not in his favour and spent 600 pounds or something just on fuel. For the next 3 weeks he was constantly talking about getting an electric engine and putting more solar panels up, but then settled with a sad "It's not feasable. I can't carry that many batteries with me.".
But you can go completely off grid once the batteries are small enough for this. You got all the electricity you need, starlink for internet, watermaker for, well, water, you can fish every day, and use the electric engine. What do you really need at that point? Maybe food every now and then, but everything else is already possible to have without having to step ashore. Cool times to live in!
Kelpie
Well-Known Member
We live fairly off grid already.
Rainwater collection, 1200w of solar allowing electric cooking, and a sailing rig for the dinghy meaning we don't use the outboard much. We very occasionally catch fish too... but it's quite hard to grow onions or produce flour on a boat! We're experimenting with herbs but not really reaching harvestable quantities.
Of course we will use the engine but rarely for more than half an hour at a time, and even that could often be reduced if I wasn't fussy about giving it a decent run each time.
But we have no schedule, no time pressure, and are sailing in a place with very favourable conditions.
Rainwater collection, 1200w of solar allowing electric cooking, and a sailing rig for the dinghy meaning we don't use the outboard much. We very occasionally catch fish too... but it's quite hard to grow onions or produce flour on a boat! We're experimenting with herbs but not really reaching harvestable quantities.
Of course we will use the engine but rarely for more than half an hour at a time, and even that could often be reduced if I wasn't fussy about giving it a decent run each time.
But we have no schedule, no time pressure, and are sailing in a place with very favourable conditions.
penfold
Well-Known Member
Needing to motor 450 miles in one go is rather an edge case? 3 days motoring at 6kts with perhaps 2 fuel stops; a 35' AWB with 15kW and an arbitrary 70kWh could do the same distance in 4 days motoring with 4 charge stops of ~12hrs. Maybe ferry skippers would baulk at this but most people don't relish doing non-stop coastal pilotage for 72 hours and might like 40 winks.