Longest time/distance you've had to motor?

[jcarr]

I believe current lithium ion batteries pack about 2% of the energy per pound as a pound of diesel fuel. Understanding that electric motors are more efficient than internal combustion engines you can move that comparison from 2 percent to 7%, still not very good. So until we get the power density/pound of batteries significantly improved I would not want to be anywhere close to a lee shore in unfavorable conditions.

[a64pilot]

I had a curiously look at using Prius traction battery packs as House banks because used ones are so widely available, but there are a few issues, first they are something like 300ish volts, so getting 12V isn’t real easy, but the real issue was that they are designed primarily for high amp mini discharge events if you will, not long slow deep cycles, or so I have been told. As you likely know the Prius cycles its bank no higher than approx 80% SOC and not under 40% or close to that anyway.

It could be done, and may be the ticket, but I gave up.

Prius design life for the traction battery is 10 years or 250,000 miles. Ours is now 8 yrs old and has 215,000 miles on it. I’ll get a “rebuilt” pack when the time comes as they are far les expensive.

[dfelsent]

I was speaking with a Vendee Globe competitor the other day. They have a requirement for five hours at five knots. Electric is a possible solution for them. Lighter motor combined with expensive battery bank plus solar charging plus hydro generators weighs less than diesel plus fuel plus hydro generators. Of course remember no toilet because that weighs too much.
The energy density in Joules per Kilo is so much higher with chemical fuels than batteries.

[a64pilot]

I thought those race boats were the ones that drug a hydro generator. I didn’t know they had Solar. I guess they could build it into the deck?
Really don’t know much about them, but saw a video of one that was showing off it’s carbon fiber head.

[dfelsent]

Hydro generators for sure. At least two cause they fail when you hit something at 25 knots. Solar supplement beginning to be used more. They are on a four year cycle. The last vendee was 2016 which means the designs started in 2012. 2020 designs are being built and finalized now. The sailors want about a circumnavigation on the boat before they circumnavigate in the race.

[a64pilot]

25 kts is inconceivable to me, especially in the open Ocean in the conditions that give you enough wind, to get to 25 kts.
If I didn’t know they did it, I wouldn’t believe it’s possible.

[stevensuf]

Originally Posted by nimblemotors

I have mostly decided to not have any sails and build my boat using a hybrid drive of both gasoline and electric propulsion. There is no question that you can't beat liquid fuel for energy density. There is also no question you can't generate such fuel yourself and must go ashore to buy more of it when you run out. Solar doesn't run out, and what makes it so attractive is that sitting at anchor it continues to provide great value.
With the current collapse in the price of panels, it makes more sense than ever.

What is really needed for a yacht is a way to store a lot of generated electricity.
If you could store enough energy to travel long distances, you can generate it while at anchor until you have enough to make a passage.
Unlike for cars, a yacht system could be big and bulky and inefficient, but must be cheap and have high energy density
Current batteries are not even close. What is needed is something more like creating liquid fuel from electricity on board. I don't know of any way that is possible at present, but that is the kind of breakthrough needed.

A significant improvement would be using zinc-air batteries.
They have 4x energy density than lithium. If one can recycle zinc-oxide back into zinc using a system small enough to fit on board, it would be a big improvement.
Zinc

JackB

Old post, but keels were made of lead and some still are, batteries are lead acid , can we not make a lead battery keel, 2 birds , one stone!

a 3000kg lead acid battery would have a fair amount of storage!


My numbers might be wrong but id say at least a 100kwh f storage
add 300kg more for fuel and 300kg for engine makes 600kg more batteries for the same weight boat.
so a 42ft mono with 3600kg ballast as batteries , could store around
120kwh in its keel battery,


A 10hp petrol will push a 9000kg boat at 4-5 knots in calm weather ,a 10hp petrol is equivalent to about a 3kw 90 percent efficient electric
motor, giving a calm weather cruising range of say 40 hours at 4-6 kn,
i imagine a good sized solar bank or fleixible solar sail? or tow generator could add on!

[Training Wheels]

As this is on a multihull forum, most multihulls don’t have lead keels.